ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 51,2025 Issue 8
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- The Future Projections of Extreme Weather, Climate and Water Events and Strategic Responses
- A Review of Downburst Genesis Mechanism and Warning
- The Pattern Structure and Thermodynamic and Dynamic Processes of Severe Storms Associated with Linear Convective Gales
- Analysis on Extremity and Characteristics of the “21·7” Severe Torrential Rain in Henan Province
- Diagnostic Analysis on Water Vapor and Jet Characteristics of the July 2021 Severe Torrential Rain in Henan Province
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2025,51(8):901-913, DOI: 10.7519/j.issn.1000-0526.2025.061901
Abstract:
This article aims to explore the potential application and challenges of large language model (LLM) in weather forecasting. Through analyzing LLM application in meteorology and related industries, including knowledge retrieval, foundation models, diagnostic analysis, tool calling and text generation, the article demonstrates that LLM has tremendous potentials in improving weather forecast accuracy and business intelligence. LLM serve as powerful assistive tools for forecasters by efficiently processing massive meteorological knowledge, integrating cross-domain multi-source information, and generating customized forecast products. The effectiveness of LLM in weather forecasting can be further enhanced by building high-quality meteorological corpora, optimizing benchmark testing frameworks, and incorporating external tools. While LLM brings new technological opportunities to the meteorological field, their widespread application still requires continuous exploration and improvement in corpus quality, model optimization, and human-machine collaboration. Moreover, LLM still has limitations in understanding the spatio-temporal dynamics of atmospheric motions and issues with bias and hallucination, which need to be addressed through data cleaning, debiasing, fine-tuning, and retrieval-augmented generation techniques.
This article aims to explore the potential application and challenges of large language model (LLM) in weather forecasting. Through analyzing LLM application in meteorology and related industries, including knowledge retrieval, foundation models, diagnostic analysis, tool calling and text generation, the article demonstrates that LLM has tremendous potentials in improving weather forecast accuracy and business intelligence. LLM serve as powerful assistive tools for forecasters by efficiently processing massive meteorological knowledge, integrating cross-domain multi-source information, and generating customized forecast products. The effectiveness of LLM in weather forecasting can be further enhanced by building high-quality meteorological corpora, optimizing benchmark testing frameworks, and incorporating external tools. While LLM brings new technological opportunities to the meteorological field, their widespread application still requires continuous exploration and improvement in corpus quality, model optimization, and human-machine collaboration. Moreover, LLM still has limitations in understanding the spatio-temporal dynamics of atmospheric motions and issues with bias and hallucination, which need to be addressed through data cleaning, debiasing, fine-tuning, and retrieval-augmented generation techniques.
2025,51(8):914-927, DOI: 10.7519/j.issn.1000-0526.2025.052301
Abstract:
Heavy precipitation is one of the most widespread hazardous weather affecting the socioeconomic stability and people’s livelihoods in China. Accurately forecasting such events poses significant scientific challenges. The multi-scale nonlinear characteristics of moist physical processes make numerical weather prediction and objective corrections for precipitation become considerably more difficult than for other meteorological variables like wind and temperature. Utilizing station observations and numerical model forecasts, this paper explores the application effect of machine learning algorithm (LightGBM) in correcting 3 h accumulated precipitation forecasts for the Beijing-Tianjin-Hebei Region through strategies such as constructing and sampling precipitation datasets, inputting relevant physical features, and training on residuals. The results demonstrate that, to address the long-tailed distribution challenge of precipitation samples, when constructing the dataset it is crucial to comprehensively consider maintaining the true distribution of precipitation while moderately increasing the proportion of samples with stronger precipitation intensities. This is a key step in enhancing the correction effectiveness of heavy precipitation. Statistical tests on the independent test set show that the LightGBM correction scheme achieves significant improvements in skill scores for precipitation ranging from 0.1 mm to 20 mm compared to the raw model forecasts, and the increase rate ascends upward as the threshold rises. Statistical tests and individual case evaluations of precipitation by type show that the LightGBM correction scheme presents comprehensive adjustments in rainfall intensity and fall area in different types of precipitation forecasts. Among them, the number of forced precipitation samples by severe weather systems is relatively superior, and the correction effects on each precipitation threshold are more remarkable. Additionally, the evaluation of classified heavy precipitation indicates that it is more challenging to achieve improvements in the correction of convective heavy precipitation forced by weak weather systems, in particular in the cases with precipitation ≥15 mm. The adjustment of the fall area of precipitation is more challenging. This suggests that the unbalanced distribution of precipitation samples remains a challenge for machine learning correction. However, machine learning has shown particular promise for correcting larger magnitudes of heavy precipitation events with lower forecast accuracy from the model, that is, the lower the model’s forecast ability, the greater the room and extent for the correction improvement of machine learning. The analysis of feature importance shows that the input of physical features such as dynamics, thermodynamics and water vapor, which are closely related to precipitation, has a positive contribution to enhancing the correction score of LightGBM.
Heavy precipitation is one of the most widespread hazardous weather affecting the socioeconomic stability and people’s livelihoods in China. Accurately forecasting such events poses significant scientific challenges. The multi-scale nonlinear characteristics of moist physical processes make numerical weather prediction and objective corrections for precipitation become considerably more difficult than for other meteorological variables like wind and temperature. Utilizing station observations and numerical model forecasts, this paper explores the application effect of machine learning algorithm (LightGBM) in correcting 3 h accumulated precipitation forecasts for the Beijing-Tianjin-Hebei Region through strategies such as constructing and sampling precipitation datasets, inputting relevant physical features, and training on residuals. The results demonstrate that, to address the long-tailed distribution challenge of precipitation samples, when constructing the dataset it is crucial to comprehensively consider maintaining the true distribution of precipitation while moderately increasing the proportion of samples with stronger precipitation intensities. This is a key step in enhancing the correction effectiveness of heavy precipitation. Statistical tests on the independent test set show that the LightGBM correction scheme achieves significant improvements in skill scores for precipitation ranging from 0.1 mm to 20 mm compared to the raw model forecasts, and the increase rate ascends upward as the threshold rises. Statistical tests and individual case evaluations of precipitation by type show that the LightGBM correction scheme presents comprehensive adjustments in rainfall intensity and fall area in different types of precipitation forecasts. Among them, the number of forced precipitation samples by severe weather systems is relatively superior, and the correction effects on each precipitation threshold are more remarkable. Additionally, the evaluation of classified heavy precipitation indicates that it is more challenging to achieve improvements in the correction of convective heavy precipitation forced by weak weather systems, in particular in the cases with precipitation ≥15 mm. The adjustment of the fall area of precipitation is more challenging. This suggests that the unbalanced distribution of precipitation samples remains a challenge for machine learning correction. However, machine learning has shown particular promise for correcting larger magnitudes of heavy precipitation events with lower forecast accuracy from the model, that is, the lower the model’s forecast ability, the greater the room and extent for the correction improvement of machine learning. The analysis of feature importance shows that the input of physical features such as dynamics, thermodynamics and water vapor, which are closely related to precipitation, has a positive contribution to enhancing the correction score of LightGBM.
2025,51(8):928-940, DOI: 10.7519/j.issn.1000-0526.2025.011201
Abstract:
The refinement level of wind forecast by numerical prediction models cannot meet the needs of inland waterway transportation, and its adaptability to different regions varies. This article takes most of western hilly area and central plain area in Hubei Province, including parts of the Yangtze River waterway, as the research areas. Referring to the 10 m wind real-time product of ART_1 km, this article analyzes the adaptability of 10 m wind forecast of the European Centre for Medium-Range Weather Forecasts high-resolution atmospheric model deterministic forecasting product (EC-HRES) and the China Meteorological Administration mesoscale model forecasting product (CMA-MESO) in the research areas. A U-Net++ deep convolutional network model is constructed to achieve downscaling correction of wind speed forecast. The correction model improves the sampling module and adds waterway item and terrain item into the loss function, enhancing expressive ability and robustness of the model and improving the correction effect on the waterway. The verification result shows that this method can effectively reduce the prediction error of wind speed made by numerical prediction models in the waterway areas.
The refinement level of wind forecast by numerical prediction models cannot meet the needs of inland waterway transportation, and its adaptability to different regions varies. This article takes most of western hilly area and central plain area in Hubei Province, including parts of the Yangtze River waterway, as the research areas. Referring to the 10 m wind real-time product of ART_1 km, this article analyzes the adaptability of 10 m wind forecast of the European Centre for Medium-Range Weather Forecasts high-resolution atmospheric model deterministic forecasting product (EC-HRES) and the China Meteorological Administration mesoscale model forecasting product (CMA-MESO) in the research areas. A U-Net++ deep convolutional network model is constructed to achieve downscaling correction of wind speed forecast. The correction model improves the sampling module and adds waterway item and terrain item into the loss function, enhancing expressive ability and robustness of the model and improving the correction effect on the waterway. The verification result shows that this method can effectively reduce the prediction error of wind speed made by numerical prediction models in the waterway areas.
2025,51(8):941-953, DOI: 10.7519/j.issn.1000-0526.2025.010902
Abstract:
Based on the total irradiance data from 23 radiation observation stations in Henan Province in 2022 and CMA-WSP2.0 model products, in this paper, characteristic variables are selected by LASSO regression, training data sets and test data sets are established, and models are trained by machine learning methods (random forest, XGBoost and LightGBM) with the training data sets. Besides, the total irradiance forecasts by CMA-WSP2.0 model in Henan Province are corrected, and the corrected results are tested by site and region, by season and by total irradiance classification. The results are as follows. The three machine learning methods (random forest, XGBoost and LightGBM) have good correction effects. Compared with the CMA-WSP2.0 prediction results, the mean absolute error (MAE) and root mean square error (RMSE) are significantly reduced, and the 24 h accuracy rate and 24 h qualification rate are significantly improved. Among them, LightGBM has the best correction effect. The MAE decreases by 18.32-32.91 W·m-2, the reduction proportion of MAE decreases by 38%-56%, and the reduction proportion of RMSE decreases by 36%-52%. Moreover, the 24 h average accuracy and 24 h average qualification rate are raised by 7.3% and 5.7%, respectively. The results of regional statistics are consistent with those of the stations. For the five regions of Henan Province, the correction effect for western Henan is the best. The corrected deviation range of the three machine machine learning methods is narrower than that of the CMA-WSP2.0 test set, and the probability of the deviation distribution near zero is greater. Among the seasonal test results, the three machine learning methods have more significant correction effect for the winter prediction. For different total irradiance levels, the three machine learning methods can effectively improve the CMA-WSP2.0 prediction, but the correction effect tends to gradually weaken with the increase of total irradiance levels. These findings could provide a useful reference for improving the ability of total irradiance forecast in Henan Province.
Based on the total irradiance data from 23 radiation observation stations in Henan Province in 2022 and CMA-WSP2.0 model products, in this paper, characteristic variables are selected by LASSO regression, training data sets and test data sets are established, and models are trained by machine learning methods (random forest, XGBoost and LightGBM) with the training data sets. Besides, the total irradiance forecasts by CMA-WSP2.0 model in Henan Province are corrected, and the corrected results are tested by site and region, by season and by total irradiance classification. The results are as follows. The three machine learning methods (random forest, XGBoost and LightGBM) have good correction effects. Compared with the CMA-WSP2.0 prediction results, the mean absolute error (MAE) and root mean square error (RMSE) are significantly reduced, and the 24 h accuracy rate and 24 h qualification rate are significantly improved. Among them, LightGBM has the best correction effect. The MAE decreases by 18.32-32.91 W·m-2, the reduction proportion of MAE decreases by 38%-56%, and the reduction proportion of RMSE decreases by 36%-52%. Moreover, the 24 h average accuracy and 24 h average qualification rate are raised by 7.3% and 5.7%, respectively. The results of regional statistics are consistent with those of the stations. For the five regions of Henan Province, the correction effect for western Henan is the best. The corrected deviation range of the three machine machine learning methods is narrower than that of the CMA-WSP2.0 test set, and the probability of the deviation distribution near zero is greater. Among the seasonal test results, the three machine learning methods have more significant correction effect for the winter prediction. For different total irradiance levels, the three machine learning methods can effectively improve the CMA-WSP2.0 prediction, but the correction effect tends to gradually weaken with the increase of total irradiance levels. These findings could provide a useful reference for improving the ability of total irradiance forecast in Henan Province.
2025,51(8):954-963, DOI: 10.7519/j.issn.1000-0526.2025.041602
Abstract:
Based on the data from automatic weather stations and buoy observation stations, and ERA5 reanalysis data from 2015 to 2023, this article analyzes the characteristics of sea fog at Yangshan Port. Classification decision tree models are trained and constructed based on a comprehensive case database of sea fog events. Their forcast results are compared with those of the ECMWF model. The results indicate that the year 2016 has the highest number of foggy days, with spring and early summer being the peak season, followed by winter. During dense fog events at Yangshan Station, the dominant wind directions change from northeast to north and southeast. Southeast winds prevail during non-precipitation periods, while north winds dominate during precipitation. Monthly wind patterns alter from predominantly northerly in winter to northeasterly and southeasterly in spring. Wind direction and speed varied at different stages of sea fog. In the developing stage of sea fog, southeast winds are dominant; during the mature stage, northeast winds prevail; and during the dissipating stage, north winds dominat with high speeds. Fog events accompanied by precipitation are more frequent and long time lasting. The classification decision tree models have identified the temperature-dewpoint spread as a key factor in the formation of various sea fog types. Decision tree models demonstrate a lower miss rate and higher prediction performance than the ECMWF model, particularly in forecasting the formation and duration of advection fog. This can provide valuable insights for forecasting frontal and radiation fog events.
Based on the data from automatic weather stations and buoy observation stations, and ERA5 reanalysis data from 2015 to 2023, this article analyzes the characteristics of sea fog at Yangshan Port. Classification decision tree models are trained and constructed based on a comprehensive case database of sea fog events. Their forcast results are compared with those of the ECMWF model. The results indicate that the year 2016 has the highest number of foggy days, with spring and early summer being the peak season, followed by winter. During dense fog events at Yangshan Station, the dominant wind directions change from northeast to north and southeast. Southeast winds prevail during non-precipitation periods, while north winds dominate during precipitation. Monthly wind patterns alter from predominantly northerly in winter to northeasterly and southeasterly in spring. Wind direction and speed varied at different stages of sea fog. In the developing stage of sea fog, southeast winds are dominant; during the mature stage, northeast winds prevail; and during the dissipating stage, north winds dominat with high speeds. Fog events accompanied by precipitation are more frequent and long time lasting. The classification decision tree models have identified the temperature-dewpoint spread as a key factor in the formation of various sea fog types. Decision tree models demonstrate a lower miss rate and higher prediction performance than the ECMWF model, particularly in forecasting the formation and duration of advection fog. This can provide valuable insights for forecasting frontal and radiation fog events.
2025,51(8):964-977, DOI: 10.7519/j.issn.1000-0526.2025.041302
Abstract:
To evaluate the accuracy and operational applicability of FY-4A/4B GIIRS-retrieved temperature and humidity profiles in Guizhou, the FY-4A temperature profile and FY-4B temperature and humidity profiles are verified against sounding observations at Guiyang and Weining stations and ERA5 reanalysis data. The results indicate that, in practical operations, it is considered that only the unusable data can be eliminated, while the data with the best and better quality can be retained so as to maximize the integrity of the temperature and humidity profiles. Clouds significantly degrade GIIRS retrieval performance. Under cloudy conditions, the root mean square error of FY-4A temperature increases by 1.19℃ (clear sky) and 0.96℃ (cloud edge), FY-4B temperature increases by 1.52℃ （clear sky） and 1.21℃ (cloud edge), and specific humidity increases by 1.28 g·kg-1 (clear sky) and 0.95 g·kg-1 (cloud edge), respectively. Moreover, cloud cover also amplifies vertical data dispersion. Seasonal comparisons between sounding and satellite profiles demonstrate that FY-4A/4B captures terrain-induced differences in atmospheric stratification between Guiyang and Weining. For three regional hail events in 2023, GIIRS products agree well with sounding observations. The high-resolution profiles reveal pre-hail instability, which is “upper dry and lower wet”, offering valuable forecast indicators. However, the near-surface layer retrieval errors lead to the underestimation of convective available potential energy (CAPE) and distort low-level sounding structures. After the surface 2 m temperature and dew point temperature corrections, a large CAPE and a sounding structure conducive to the occurrence of thunderstorms and strong winds are displayed. This is a good support for the short-time forecasting and nowcasting of severe convections.
To evaluate the accuracy and operational applicability of FY-4A/4B GIIRS-retrieved temperature and humidity profiles in Guizhou, the FY-4A temperature profile and FY-4B temperature and humidity profiles are verified against sounding observations at Guiyang and Weining stations and ERA5 reanalysis data. The results indicate that, in practical operations, it is considered that only the unusable data can be eliminated, while the data with the best and better quality can be retained so as to maximize the integrity of the temperature and humidity profiles. Clouds significantly degrade GIIRS retrieval performance. Under cloudy conditions, the root mean square error of FY-4A temperature increases by 1.19℃ (clear sky) and 0.96℃ (cloud edge), FY-4B temperature increases by 1.52℃ （clear sky） and 1.21℃ (cloud edge), and specific humidity increases by 1.28 g·kg-1 (clear sky) and 0.95 g·kg-1 (cloud edge), respectively. Moreover, cloud cover also amplifies vertical data dispersion. Seasonal comparisons between sounding and satellite profiles demonstrate that FY-4A/4B captures terrain-induced differences in atmospheric stratification between Guiyang and Weining. For three regional hail events in 2023, GIIRS products agree well with sounding observations. The high-resolution profiles reveal pre-hail instability, which is “upper dry and lower wet”, offering valuable forecast indicators. However, the near-surface layer retrieval errors lead to the underestimation of convective available potential energy (CAPE) and distort low-level sounding structures. After the surface 2 m temperature and dew point temperature corrections, a large CAPE and a sounding structure conducive to the occurrence of thunderstorms and strong winds are displayed. This is a good support for the short-time forecasting and nowcasting of severe convections.
2025,51(8):978-992, DOI: 10.7519/j.issn.1000-0526.2025.031902
Abstract:
Based on C-band weather radar products and multi-source observations, the persistent severe storm weather process and two major rainstorm cells in southwest Yunnan during 13-15 March 2023 are analyzed. The results indicate that this severe storm weather process occurred in the circulation background of the surface cold front’s retreating eastward, the establishment and intensification of the southwesterly jet in the low (upper) air, and the persistent intrusion of the mid-level northwesterly flow, and the storm mainly developed and intensified near the crossing area of the mid- and high-altitude jets. The continuous and stable transport of the low-level warm advection and the mid-level cold advection in southwest Yunnan intensified the unstable stratification of the ambient atmosphere. The convective available potential energy (CAPE) was 826.6-1481.6 J·kg-1, the vertical wind shears from 0 to 3 km, and 0 to 6 km were 14.4-19.9 m·s-1 and 27.6-34.5 m·s-1, respectively. The high unstable stratification and the strong vertical wind shear provided good ambient condition for the formation, development and maintenance of the catastrophic storms. The daytime storm was triggered by the coupling of southerly wind uplift forced by warm advection with weak surface convergence lines. The significant thermal and moisture difference on either side of the Wuliang Mountains enhanced the storm’s development. Comparatively, the nighttime storm initially formed near the mid-to-low-level baroclinic frontogenesis zone, triggered by upslope lifting during its moving eastward and intensified under the influence of the low-level southwesterly jet. Under the influence of diurnal difference and diverse topographic forcing, the radar echo characteristics of the storm cells exhibited distinct features. Storm cell No.1 displayed radar echo morphologies such as an inflow notch, a bounded weak echo region (BWER), and a “V” notch, with radial velocity indicating a mesocyclone structure. During the hailfall period, the average composite reflectivity was 60.5 dBz, the average vertically integrated liquid (VIL) was 36.1 kg·m-2, and the average VIL density (VILD) was 4.0 g·m-3. In contrast, storm cell No.2 had a prominent rear-inflow jet and a forward-flank inflow notch, with more pronounced topographic responses in its echo. After crossing the Lancang River, the strong echo area, VIL, and VILD increased abruptly, with VILD rising from 1.7 g·m-3 to 4.5 g·m-3. The life cycles and surface severe weather manifestations of the storm cells differed significantly. Storm cell No.1 had a lifespan of 6 h, accompanied by continuous hailfall during its influence period, with thunderstorm winds observed before and after its passage. The precipitation phase transitioned to a mix of hail and short-term heavy rainfall exceeding 20 mm·h-1 in the later stage. Storm cell No.2 had a lifespan of 3 h, with hailfall occurring only in the later stage of its development. The other types of convective weather were less intense.
Based on C-band weather radar products and multi-source observations, the persistent severe storm weather process and two major rainstorm cells in southwest Yunnan during 13-15 March 2023 are analyzed. The results indicate that this severe storm weather process occurred in the circulation background of the surface cold front’s retreating eastward, the establishment and intensification of the southwesterly jet in the low (upper) air, and the persistent intrusion of the mid-level northwesterly flow, and the storm mainly developed and intensified near the crossing area of the mid- and high-altitude jets. The continuous and stable transport of the low-level warm advection and the mid-level cold advection in southwest Yunnan intensified the unstable stratification of the ambient atmosphere. The convective available potential energy (CAPE) was 826.6-1481.6 J·kg-1, the vertical wind shears from 0 to 3 km, and 0 to 6 km were 14.4-19.9 m·s-1 and 27.6-34.5 m·s-1, respectively. The high unstable stratification and the strong vertical wind shear provided good ambient condition for the formation, development and maintenance of the catastrophic storms. The daytime storm was triggered by the coupling of southerly wind uplift forced by warm advection with weak surface convergence lines. The significant thermal and moisture difference on either side of the Wuliang Mountains enhanced the storm’s development. Comparatively, the nighttime storm initially formed near the mid-to-low-level baroclinic frontogenesis zone, triggered by upslope lifting during its moving eastward and intensified under the influence of the low-level southwesterly jet. Under the influence of diurnal difference and diverse topographic forcing, the radar echo characteristics of the storm cells exhibited distinct features. Storm cell No.1 displayed radar echo morphologies such as an inflow notch, a bounded weak echo region (BWER), and a “V” notch, with radial velocity indicating a mesocyclone structure. During the hailfall period, the average composite reflectivity was 60.5 dBz, the average vertically integrated liquid (VIL) was 36.1 kg·m-2, and the average VIL density (VILD) was 4.0 g·m-3. In contrast, storm cell No.2 had a prominent rear-inflow jet and a forward-flank inflow notch, with more pronounced topographic responses in its echo. After crossing the Lancang River, the strong echo area, VIL, and VILD increased abruptly, with VILD rising from 1.7 g·m-3 to 4.5 g·m-3. The life cycles and surface severe weather manifestations of the storm cells differed significantly. Storm cell No.1 had a lifespan of 6 h, accompanied by continuous hailfall during its influence period, with thunderstorm winds observed before and after its passage. The precipitation phase transitioned to a mix of hail and short-term heavy rainfall exceeding 20 mm·h-1 in the later stage. Storm cell No.2 had a lifespan of 3 h, with hailfall occurring only in the later stage of its development. The other types of convective weather were less intense.
2025,51(8):993-1005, DOI: 10.7519/j.issn.1000-0526.2025.010901
Abstract:
Based on C-band weather radar products and multi-source observations, the persistent severe storm weather process and two major rainstorm cells in southwest Yunnan during 13-15 March 2023 are analyzed. The results indicate that this severe storm weather process occurred in the circulation background of the surface cold front’s retreating eastward, the establishment and intensification of the southwesterly jet in the low (upper) air, and the persistent intrusion of the mid-level northwesterly flow, and the storm mainly developed and intensified near the crossing area of the mid- and high-altitude jets. The continuous and stable transport of the low-level warm advection and the mid-level cold advection in southwest Yunnan intensified the unstable stratification of the ambient atmosphere. The convective available potential energy (CAPE) was 826.6-1481.6 J·kg-1, the vertical wind shears from 0 to 3 km, and 0 to 6 km were 14.4-19.9 m·s-1 and 27.6-34.5 m·s-1, respectively. The high unstable stratification and the strong vertical wind shear provided good ambient condition for the formation, development and maintenance of the catastrophic storms. The daytime storm was triggered by the coupling of southerly wind uplift forced by warm advection with weak surface convergence lines. The significant thermal and moisture difference on either side of the Wuliang Mountains enhanced the storm’s development. Comparatively, the nighttime storm initially formed near the mid-to-low-level baroclinic frontogenesis zone, triggered by upslope lifting during its moving eastward and intensified under the influence of the low-level southwesterly jet. Under the influence of diurnal difference and diverse topographic forcing, the radar echo characteristics of the storm cells exhibited distinct features. Storm cell No.1 displayed radar echo morphologies such as an inflow notch, a bounded weak echo region (BWER), and a “V” notch, with radial velocity indicating a mesocyclone structure. During the hailfall period, the average composite reflectivity was 60.5 dBz, the average vertically integrated liquid (VIL) was 36.1 kg·m-2, and the average VIL density (VILD) was 4.0 g·m-3. In contrast, storm cell No.2 had a prominent rear-inflow jet and a forward-flank inflow notch, with more pronounced topographic responses in its echo. After crossing the Lancang River, the strong echo area, VIL, and VILD increased abruptly, with VILD rising from 1.7 g·m-3 to 4.5 g·m-3. The life cycles and surface severe weather manifestations of the storm cells differed significantly. Storm cell No.1 had a lifespan of 6 h, accompanied by continuous hailfall during its influence period, with thunderstorm winds observed before and after its passage. The precipitation phase transitioned to a mix of hail and short-term heavy rainfall exceeding 20 mm·h-1 in the later stage. Storm cell No.2 had a lifespan of 3 h, with hailfall occurring only in the later stage of its development. The other types of convective weather were less intense.
Based on C-band weather radar products and multi-source observations, the persistent severe storm weather process and two major rainstorm cells in southwest Yunnan during 13-15 March 2023 are analyzed. The results indicate that this severe storm weather process occurred in the circulation background of the surface cold front’s retreating eastward, the establishment and intensification of the southwesterly jet in the low (upper) air, and the persistent intrusion of the mid-level northwesterly flow, and the storm mainly developed and intensified near the crossing area of the mid- and high-altitude jets. The continuous and stable transport of the low-level warm advection and the mid-level cold advection in southwest Yunnan intensified the unstable stratification of the ambient atmosphere. The convective available potential energy (CAPE) was 826.6-1481.6 J·kg-1, the vertical wind shears from 0 to 3 km, and 0 to 6 km were 14.4-19.9 m·s-1 and 27.6-34.5 m·s-1, respectively. The high unstable stratification and the strong vertical wind shear provided good ambient condition for the formation, development and maintenance of the catastrophic storms. The daytime storm was triggered by the coupling of southerly wind uplift forced by warm advection with weak surface convergence lines. The significant thermal and moisture difference on either side of the Wuliang Mountains enhanced the storm’s development. Comparatively, the nighttime storm initially formed near the mid-to-low-level baroclinic frontogenesis zone, triggered by upslope lifting during its moving eastward and intensified under the influence of the low-level southwesterly jet. Under the influence of diurnal difference and diverse topographic forcing, the radar echo characteristics of the storm cells exhibited distinct features. Storm cell No.1 displayed radar echo morphologies such as an inflow notch, a bounded weak echo region (BWER), and a “V” notch, with radial velocity indicating a mesocyclone structure. During the hailfall period, the average composite reflectivity was 60.5 dBz, the average vertically integrated liquid (VIL) was 36.1 kg·m-2, and the average VIL density (VILD) was 4.0 g·m-3. In contrast, storm cell No.2 had a prominent rear-inflow jet and a forward-flank inflow notch, with more pronounced topographic responses in its echo. After crossing the Lancang River, the strong echo area, VIL, and VILD increased abruptly, with VILD rising from 1.7 g·m-3 to 4.5 g·m-3. The life cycles and surface severe weather manifestations of the storm cells differed significantly. Storm cell No.1 had a lifespan of 6 h, accompanied by continuous hailfall during its influence period, with thunderstorm winds observed before and after its passage. The precipitation phase transitioned to a mix of hail and short-term heavy rainfall exceeding 20 mm·h-1 in the later stage. Storm cell No.2 had a lifespan of 3 h, with hailfall occurring only in the later stage of its development. The other types of convective weather were less intense.
2025,51(8):1006-1017, DOI: 10.7519/j.issn.1000-0526.2025.021801
Abstract:
Based on the hourly precipitation data from 122 national meteorological stations in Shandong Province from 1966 to 2023, the frequency variations of heavy precipitation are analyzed. Different marginal distribution functions are used to fit the duration and amount of precipitation, and the change patterns of the return periods of heavy precipitation with different durations are investigated based on Copula function. The results are as follows. There exists a significant dependence relation between the duration and amount of heavy precipitation, which can be fitted well using generalized extreme values and logarithmic normal distribution functions. The Gumbel Copula and Clayton Copula functions are suitable for portraying the dependence structure of the binary variables of the short-time heavy precipitation in Shandong. However, the Clayton Copula function is more appropriate when the precipitation lasts for more than 8 h. The return period estimated by daily precipitation may seriously underestimate the hazard of short-time heavy precipitation. For a short-time heavy precipitation event under the same hazard-bearing condition, the shorter the duration, the longer the joint return period. The high-value areas of joint return period estimated by the Copula function gradually narrow down from the east and the south of Shandong to the east of Shandong, along with the increase of precipitation duration. Especially, the hazard of heavy precipitation that comes along once every 60 years is higher in the east and the south of Shandong. This method can more scientifically describe the disaster risks of heavy precipitation in different scenarios, especially in the short-time heavy precipitation scenario, so it can provide a scientific reference for disaster prevention and mitigation planning as well as disaster risk managing in Shandong.
Based on the hourly precipitation data from 122 national meteorological stations in Shandong Province from 1966 to 2023, the frequency variations of heavy precipitation are analyzed. Different marginal distribution functions are used to fit the duration and amount of precipitation, and the change patterns of the return periods of heavy precipitation with different durations are investigated based on Copula function. The results are as follows. There exists a significant dependence relation between the duration and amount of heavy precipitation, which can be fitted well using generalized extreme values and logarithmic normal distribution functions. The Gumbel Copula and Clayton Copula functions are suitable for portraying the dependence structure of the binary variables of the short-time heavy precipitation in Shandong. However, the Clayton Copula function is more appropriate when the precipitation lasts for more than 8 h. The return period estimated by daily precipitation may seriously underestimate the hazard of short-time heavy precipitation. For a short-time heavy precipitation event under the same hazard-bearing condition, the shorter the duration, the longer the joint return period. The high-value areas of joint return period estimated by the Copula function gradually narrow down from the east and the south of Shandong to the east of Shandong, along with the increase of precipitation duration. Especially, the hazard of heavy precipitation that comes along once every 60 years is higher in the east and the south of Shandong. This method can more scientifically describe the disaster risks of heavy precipitation in different scenarios, especially in the short-time heavy precipitation scenario, so it can provide a scientific reference for disaster prevention and mitigation planning as well as disaster risk managing in Shandong.
2025,51(8):1018-1028, DOI: 10.7519/j.issn.1000-0526.2025.072801
Abstract:
The main characteristics of the general circulation in May 2025 are that the polar vortex in the Northern Hemisphere was partially mono polar with stronger intensity than usual. The circulation transformed from a three wave pattern in winter into a four wave pattern in summer. The western Pacific subtropical high was stronger, located more westerly than in normal years, while the south branch trough was weaker than usual. The South China Sea summer monsoon erupted in the 6th pentad (29 May) of May, 10 days later than in normal years. The monthly average temperature across China was 17.3℃, 0.8℃ higher than normal, so it was recorded as the third highest for the same historical period since 1961. The monthly average precipitation was 77.6 mm, 10% more than normal. During this month, six torrential rain and severe convection processes occurred in China, with precipitation at many stations breaking their historical extremes, causing floods and secondary geological disasters in Guizhou, Guangxi, Guangdong, Hunan, Jiangxi provinces and other regions. On 4 May, thunderstorm gale at speed of 44.7 m·s-1 was monitored in Qianxi City, Guizhou Province. On 8 May, EF1 tornadoes occurred in Qidong County and Liling City, Hunan Province. In additionThe main characteristics of the general circulation in May 2025 are that the polar vortex in the Northern Hemisphere was partially mono-polar with stronger intensity than usual. The circulation transformed from a three-wave pattern in winter into a four-wave pattern in summer. The western Pacific subtropical high was stronger, located more westerly than in normal years, while the south branch trough was weaker than usual. The South China Sea summer monsoon erupted in the 6th pentad (29 May) of May, 10 days later than in normal years. The monthly average temperature across China was 17.3℃, 0.8℃ higher than normal, so it was recorded as the third highest for the same historical period since 1961. The monthly average precipitation was 77.6 mm, 10% more than normal. During this month, six torrential rain and severe convection processes occurred in China, with precipitation at many stations breaking their historical extremes, causing floods and secondary geological disasters in Guizhou, Guangxi, Guangdong, Hunan, Jiangxi provinces and other regions. On 4 May, thunderstorm gale at speed of 44.7 m·s-1 was monitored in Qianxi City, Guizhou Province. On 8 May, EF1 tornadoes occurred in Qidong County and Liling City, Hunan Province. In addition, there were five sand-dust events affecting northern China during this month, which are noticeably more than the average for the same period from 2000 to 2024. , there were five sand dust events affecting northern China during this month, which are noticeably more than the average for the same period from 2000 to 2024.
The main characteristics of the general circulation in May 2025 are that the polar vortex in the Northern Hemisphere was partially mono polar with stronger intensity than usual. The circulation transformed from a three wave pattern in winter into a four wave pattern in summer. The western Pacific subtropical high was stronger, located more westerly than in normal years, while the south branch trough was weaker than usual. The South China Sea summer monsoon erupted in the 6th pentad (29 May) of May, 10 days later than in normal years. The monthly average temperature across China was 17.3℃, 0.8℃ higher than normal, so it was recorded as the third highest for the same historical period since 1961. The monthly average precipitation was 77.6 mm, 10% more than normal. During this month, six torrential rain and severe convection processes occurred in China, with precipitation at many stations breaking their historical extremes, causing floods and secondary geological disasters in Guizhou, Guangxi, Guangdong, Hunan, Jiangxi provinces and other regions. On 4 May, thunderstorm gale at speed of 44.7 m·s-1 was monitored in Qianxi City, Guizhou Province. On 8 May, EF1 tornadoes occurred in Qidong County and Liling City, Hunan Province. In additionThe main characteristics of the general circulation in May 2025 are that the polar vortex in the Northern Hemisphere was partially mono-polar with stronger intensity than usual. The circulation transformed from a three-wave pattern in winter into a four-wave pattern in summer. The western Pacific subtropical high was stronger, located more westerly than in normal years, while the south branch trough was weaker than usual. The South China Sea summer monsoon erupted in the 6th pentad (29 May) of May, 10 days later than in normal years. The monthly average temperature across China was 17.3℃, 0.8℃ higher than normal, so it was recorded as the third highest for the same historical period since 1961. The monthly average precipitation was 77.6 mm, 10% more than normal. During this month, six torrential rain and severe convection processes occurred in China, with precipitation at many stations breaking their historical extremes, causing floods and secondary geological disasters in Guizhou, Guangxi, Guangdong, Hunan, Jiangxi provinces and other regions. On 4 May, thunderstorm gale at speed of 44.7 m·s-1 was monitored in Qianxi City, Guizhou Province. On 8 May, EF1 tornadoes occurred in Qidong County and Liling City, Hunan Province. In addition, there were five sand-dust events affecting northern China during this month, which are noticeably more than the average for the same period from 2000 to 2024. , there were five sand dust events affecting northern China during this month, which are noticeably more than the average for the same period from 2000 to 2024.
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Available online: August 27, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.012002
Abstract:
Tropical cyclones (known as typhoons in the Northwest Pacific region) are one of the top ten natural disasters, China is located on the west coast of the North Pacific and is deeply affected by typhoons. China also is one of the countries with severe tropical cyclone disasters in the world. China attaches great importance to cooperation with the international community while focusing on improving its own typhoon monitoring, prediction, warning, and disaster prevention capabilities. Through long-term cooperation with the international typhoon community, China has benefited greatly and made special contributions to the development of international typhoon disaster prevention and reduction, China is a staunch supporter, active participant, and important contributor to international cooperation in Typhoon disaster prevention and reduction. In the past 50 years, China (the mainland) has achieved fruitful results in international cooperation on typhoon related events, and has also display a series of animated scrolls that resonate with the quickly development of typhoon disaster prevention and reduction in China and internationally.
Tropical cyclones (known as typhoons in the Northwest Pacific region) are one of the top ten natural disasters, China is located on the west coast of the North Pacific and is deeply affected by typhoons. China also is one of the countries with severe tropical cyclone disasters in the world. China attaches great importance to cooperation with the international community while focusing on improving its own typhoon monitoring, prediction, warning, and disaster prevention capabilities. Through long-term cooperation with the international typhoon community, China has benefited greatly and made special contributions to the development of international typhoon disaster prevention and reduction, China is a staunch supporter, active participant, and important contributor to international cooperation in Typhoon disaster prevention and reduction. In the past 50 years, China (the mainland) has achieved fruitful results in international cooperation on typhoon related events, and has also display a series of animated scrolls that resonate with the quickly development of typhoon disaster prevention and reduction in China and internationally.
Available online: August 25, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.022001
Abstract:
A documented tornado outbreak event occurred in Shandong province on 5 July,2024, influenced by the upper-level trough and Huang-Huai cyclone.The event notably impacted Heze City, where tornadoes are rarely reported, causing substantial casualties and property damage. This study analyzes the development and evolution of tornadoes in Dongming and Juancheng counties of Heze City, along with their environmental conditions and mesoscale characteristics, based on disaster investigations, online video and photo evidence, ERA5 reanalysis data, and dual-polarization radar observations. The main conclusions are as follows: according to the comprehensive assessment, the maximum intensity of the tornadoes in Dongming and Juancheng Counties reached peak intensities corresponding to strong tornado (equivalent to EF2-EF3 level),which located approximately 50 km northeast of the Huang-Huai cyclone center. The environment features conducive to the formation of supercell tornadoes included abundant water vapor, low lifting condensation level, sufficient convective instability energy, strong storm-relative helicity, and strong vertical wind shear. Meso-β-scale convergence line and appropriate cold pool intensity provided favorable conditions for the initiation, development of the tornadic storm, and the strengthening of near-surface vertical vorticity. Both tornadoes originated from the same southwest-northeast moving supercell, characterized by:(1)a robust echo centroid near 5 km altitude,(2)a persistent, deep mesocyclone with tilted vertical structure.The tornadoes appeared at the top of the hook echo of the supercell, and the period of tornado occurrence was accompanied by signals such as the reduction of mesocyclone scale and the enhancement of cyclonic vortex.The radar detected both tornado vortex signature(TVS) and tornado debris signature(TDS) for the two tornadoes, with the earliest detection of TVS being 15 minutes and 5 minutes ahead of the tornado occurrence time,respectively.During the occurrence of tornado, the correlation coefficient corresponding to the vortex features rapidly decreases. The lowest value (0.46) appears at the time when ground damage is most severe, which may be attributed to the mixing of hydrometeor particles and a large amount of debris carried by the strong updraft, as well as the reduction in signal-to-noise ratio caused by the intense updraft. After the tornado dissipated, the low CC value characteristic persisted for more than 15 minutes. These findings enhance understanding of Huang-Huai cyclone-associated tornadoes and provide operational guidance for tornado monitoring and warning systems.
A documented tornado outbreak event occurred in Shandong province on 5 July,2024, influenced by the upper-level trough and Huang-Huai cyclone.The event notably impacted Heze City, where tornadoes are rarely reported, causing substantial casualties and property damage. This study analyzes the development and evolution of tornadoes in Dongming and Juancheng counties of Heze City, along with their environmental conditions and mesoscale characteristics, based on disaster investigations, online video and photo evidence, ERA5 reanalysis data, and dual-polarization radar observations. The main conclusions are as follows: according to the comprehensive assessment, the maximum intensity of the tornadoes in Dongming and Juancheng Counties reached peak intensities corresponding to strong tornado (equivalent to EF2-EF3 level),which located approximately 50 km northeast of the Huang-Huai cyclone center. The environment features conducive to the formation of supercell tornadoes included abundant water vapor, low lifting condensation level, sufficient convective instability energy, strong storm-relative helicity, and strong vertical wind shear. Meso-β-scale convergence line and appropriate cold pool intensity provided favorable conditions for the initiation, development of the tornadic storm, and the strengthening of near-surface vertical vorticity. Both tornadoes originated from the same southwest-northeast moving supercell, characterized by:(1)a robust echo centroid near 5 km altitude,(2)a persistent, deep mesocyclone with tilted vertical structure.The tornadoes appeared at the top of the hook echo of the supercell, and the period of tornado occurrence was accompanied by signals such as the reduction of mesocyclone scale and the enhancement of cyclonic vortex.The radar detected both tornado vortex signature(TVS) and tornado debris signature(TDS) for the two tornadoes, with the earliest detection of TVS being 15 minutes and 5 minutes ahead of the tornado occurrence time,respectively.During the occurrence of tornado, the correlation coefficient corresponding to the vortex features rapidly decreases. The lowest value (0.46) appears at the time when ground damage is most severe, which may be attributed to the mixing of hydrometeor particles and a large amount of debris carried by the strong updraft, as well as the reduction in signal-to-noise ratio caused by the intense updraft. After the tornado dissipated, the low CC value characteristic persisted for more than 15 minutes. These findings enhance understanding of Huang-Huai cyclone-associated tornadoes and provide operational guidance for tornado monitoring and warning systems.
Available online: August 19, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.052601
Abstract:
Significant tornadoes associated with supercells can cause severe disasters. Issuing tornado warnings is challenging. Therefore, it is essential to study the detailed echo structure of supercells. Based on the observations of S-band Doppler polarimetric radar, 9 significant tornadic supercells are compared with 9 non-tornaic supercells. The results indicate significant differences between them. The detail results are as follows. 1）In tornadic supercells, the differential reflectivity ZDR arc extends toward the hook echo, and the area of hail in the mid-to-low levels is smaller than in non-tornadic supercells. 2）The average separation distance between the specific differential phase KDP foot centroid and ZDR arc centroid in the low-level is larger in tornadic supercells than in non-tornadic supercells. 3）In tornadic supercells,the low-level mesocyclone intensifies significantly. Additionally, before the tornado occurs, the mid-level mesocyclone core remains at relatively low heights, averaging 4.2 km at 24 minutes prior and 3.1 km at 6 minutes prior to the tornado formation. The aforementioned differences require further confirmation through more cases to provide additional evidence for in-depth research on the relationship between the echo structure characteristics of supercells and the mechanisms of tornado formation.
Significant tornadoes associated with supercells can cause severe disasters. Issuing tornado warnings is challenging. Therefore, it is essential to study the detailed echo structure of supercells. Based on the observations of S-band Doppler polarimetric radar, 9 significant tornadic supercells are compared with 9 non-tornaic supercells. The results indicate significant differences between them. The detail results are as follows. 1）In tornadic supercells, the differential reflectivity ZDR arc extends toward the hook echo, and the area of hail in the mid-to-low levels is smaller than in non-tornadic supercells. 2）The average separation distance between the specific differential phase KDP foot centroid and ZDR arc centroid in the low-level is larger in tornadic supercells than in non-tornadic supercells. 3）In tornadic supercells,the low-level mesocyclone intensifies significantly. Additionally, before the tornado occurs, the mid-level mesocyclone core remains at relatively low heights, averaging 4.2 km at 24 minutes prior and 3.1 km at 6 minutes prior to the tornado formation. The aforementioned differences require further confirmation through more cases to provide additional evidence for in-depth research on the relationship between the echo structure characteristics of supercells and the mechanisms of tornado formation.
Available online: August 18, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.041301
Abstract:
Based on the data from the South China outfield experiment in summer 2023, the contribution of assimilating Beidou sounding data from the Guangdong network to forecasting Typhoon Saola (2309) was studied and analyzed using the three-dimensional variational assimilation method of the Weather Research and Forecasting Model (WRF) and its Variational Assimilation System (WRFDA). The application prospects of the fully operationalized new Beidou sounding observation system were also explored. The study found that Beidou sounding has basically the same quality as L-band sounding at the same station, as well as ERA5 reanalysis data and FNL analysis field data, and has high observational value. The effective assimilation of Beidou sounding data has adjusted the temperature, humidity, and wind fields of the background field to varying degrees, significantly improving the analysis field. It also has corresponding improvements in the forecast of the typhoon"s track, intensity, and precipitation, with the track error improving by 11.87% compared to the non-assimilated Beidou sounding.
Based on the data from the South China outfield experiment in summer 2023, the contribution of assimilating Beidou sounding data from the Guangdong network to forecasting Typhoon Saola (2309) was studied and analyzed using the three-dimensional variational assimilation method of the Weather Research and Forecasting Model (WRF) and its Variational Assimilation System (WRFDA). The application prospects of the fully operationalized new Beidou sounding observation system were also explored. The study found that Beidou sounding has basically the same quality as L-band sounding at the same station, as well as ERA5 reanalysis data and FNL analysis field data, and has high observational value. The effective assimilation of Beidou sounding data has adjusted the temperature, humidity, and wind fields of the background field to varying degrees, significantly improving the analysis field. It also has corresponding improvements in the forecast of the typhoon"s track, intensity, and precipitation, with the track error improving by 11.87% compared to the non-assimilated Beidou sounding.
Available online: August 18, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.072901
Abstract:
The Spring Festival occurs between January 20th and February 26th, which is the golden week of tourism, bring high intensity tourism flow. The Spring Festival tourism show climate driven characteristics. The climate conditions during the Spring Festival is important to tourism. Human comfort index and trend analysis method were used to analyze the spatial pattern and temporal variation characteristics of favorable and unfavorable China"s tourism climate conditions in the Spring Festival. The results showed that during the Spring Festival, there is a significant north-south difference in occurred between January 20th and February 26th, during which the spatial pattern of temperature and precipitation in China showed significant north-south differences. The average temperature in most areas south of the Yangtze River was above 5 ℃, while in most parts of Heilongjiang and northeastern Inner Mongolia it was below -20 15 ℃. The precipitation was mainly concentrated in Jiangnan and the central eastern part of South China, with the northeastern part of Jiangxi exceeding 140mm. The number of human comfort day was more than 10 days in most parts of South China, Yunnan, and southern Sichuan, which was beneficial for winter resort. The number of snow cover day was more than 15 days in the majority of Northeast China, central and northeastern Inner Mongolia, and northern Xinjiang, which was conducive to ice-snow tourism. Precipitation and fog mainly affected tourism in southern China, while strong winds and cold weather mainly affected northern China. Since 1961, during the Spring Festival period, the average temperature in China has significantly increased, and the number of cold days and windy days has shown a significant decreasing trend. However, there has been no significant change in rainy days, foggy days, and snow covered days. The reduction of strong winds and cold days in most parts of China is conducive to Spring Festival tourism activities, especially for ice-snow tourism in north China. In the eastern part of South China, and most parts of Yunnan and southern Sichuan, the number of comfortable days has increased while the number of rainy and foggy days has decreased, which obviously improved winter resort tourism climate conditions. Overall, the climate conditions for winter resort and ice-snow tourism during the Spring Festival improves obviously, which is important for transforming climate resources into tourism economy and promoting the development of featured tourism in various regions.
The Spring Festival occurs between January 20th and February 26th, which is the golden week of tourism, bring high intensity tourism flow. The Spring Festival tourism show climate driven characteristics. The climate conditions during the Spring Festival is important to tourism. Human comfort index and trend analysis method were used to analyze the spatial pattern and temporal variation characteristics of favorable and unfavorable China"s tourism climate conditions in the Spring Festival. The results showed that during the Spring Festival, there is a significant north-south difference in occurred between January 20th and February 26th, during which the spatial pattern of temperature and precipitation in China showed significant north-south differences. The average temperature in most areas south of the Yangtze River was above 5 ℃, while in most parts of Heilongjiang and northeastern Inner Mongolia it was below -20 15 ℃. The precipitation was mainly concentrated in Jiangnan and the central eastern part of South China, with the northeastern part of Jiangxi exceeding 140mm. The number of human comfort day was more than 10 days in most parts of South China, Yunnan, and southern Sichuan, which was beneficial for winter resort. The number of snow cover day was more than 15 days in the majority of Northeast China, central and northeastern Inner Mongolia, and northern Xinjiang, which was conducive to ice-snow tourism. Precipitation and fog mainly affected tourism in southern China, while strong winds and cold weather mainly affected northern China. Since 1961, during the Spring Festival period, the average temperature in China has significantly increased, and the number of cold days and windy days has shown a significant decreasing trend. However, there has been no significant change in rainy days, foggy days, and snow covered days. The reduction of strong winds and cold days in most parts of China is conducive to Spring Festival tourism activities, especially for ice-snow tourism in north China. In the eastern part of South China, and most parts of Yunnan and southern Sichuan, the number of comfortable days has increased while the number of rainy and foggy days has decreased, which obviously improved winter resort tourism climate conditions. Overall, the climate conditions for winter resort and ice-snow tourism during the Spring Festival improves obviously, which is important for transforming climate resources into tourism economy and promoting the development of featured tourism in various regions.
Available online: August 16, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.063002
Abstract:
This study comprehensively applied multi-source high-frequency observational data to analyze the genesis, development, and applicability in nowcasting and warning of a localized severe convective event that occurred in Beijing on August 27, 2020. Utilizing various high-frequency detection instruments including microwave radiometers, wind profile radars, S-band Doppler radars, X-band dual-polarization radars, and a three-dimensional lightning positioning system, the evolutionary characteristics and warning indicators during thunderstorm initiation, development, and dissipation stages were investigated. The results demonstrated: 1) Microwave radiometer-retrieved temperature, humidity, and stability parameters (K-index, SI-index) showed significant variations 30-120 minutes prior to the convective outbreak, effectively indicating energy accumulation. 2) Enhanced vertical wind shear and low-level warm advection detected by wind profile radars provided 55-120 minute lead time in reflecting dynamic lifting conditions. 3) S/X-band radar observations of echo overhang structures, centroid height variations, and dual-polarization parameters (ZDR, KDP) enabled identification of hail growth regions, achieving 12-37 minutes lead time for hail and severe wind warnings. 4) Lightning jump signals (2σ algorithm) exhibited strong correlation with severe weather (hail and winds), with the first jump providing 52-minute warning lead time for hail. Validation with four other 2020 convective cases confirmed that synergistic application of multi-source observations can overcome limitations of single-instrument detection, enabling dynamic tracking of environmental energy, storm structure, and lightning activities, thereby providing valuable references for short-term forecasting.
This study comprehensively applied multi-source high-frequency observational data to analyze the genesis, development, and applicability in nowcasting and warning of a localized severe convective event that occurred in Beijing on August 27, 2020. Utilizing various high-frequency detection instruments including microwave radiometers, wind profile radars, S-band Doppler radars, X-band dual-polarization radars, and a three-dimensional lightning positioning system, the evolutionary characteristics and warning indicators during thunderstorm initiation, development, and dissipation stages were investigated. The results demonstrated: 1) Microwave radiometer-retrieved temperature, humidity, and stability parameters (K-index, SI-index) showed significant variations 30-120 minutes prior to the convective outbreak, effectively indicating energy accumulation. 2) Enhanced vertical wind shear and low-level warm advection detected by wind profile radars provided 55-120 minute lead time in reflecting dynamic lifting conditions. 3) S/X-band radar observations of echo overhang structures, centroid height variations, and dual-polarization parameters (ZDR, KDP) enabled identification of hail growth regions, achieving 12-37 minutes lead time for hail and severe wind warnings. 4) Lightning jump signals (2σ algorithm) exhibited strong correlation with severe weather (hail and winds), with the first jump providing 52-minute warning lead time for hail. Validation with four other 2020 convective cases confirmed that synergistic application of multi-source observations can overcome limitations of single-instrument detection, enabling dynamic tracking of environmental energy, storm structure, and lightning activities, thereby providing valuable references for short-term forecasting.
Available online: August 14, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.081401
Abstract:
In recent years, the X-band dual-polarization phased array weather radars (X-PAR) have been densely deployed in multiple regions across China, with the advantage of high spatiotemporal resolution. However, the data quality and limited coverage of single X-PAR are restricted factors of its application. Taking advantage of the radar network consist of the S-band dual-polarization weather radar (S-POL) and X-PAR, the research aims to obtain precise three-dimensional observation results. In this study, the data quality evaluation parameters were constructed for the radar variables of radars with different wavelengths to achieve the interpolation and mosaicking of single-wavelength radar networks. Furthermore, by calculating the deviations between the S-POL and X-PAR radar mosaics, the S-POL mosaic was taken as a background field with the low-resolution and credible characteristic, and integrate the observed detail structures from the X-PAR mosaic, the fusion of the S-POL and X-PAR radar mosaics was realized. The results show that by calculating the data quality evaluation parameters, combining the spatial distance from radar bins to grid points, and setting weights to perform interpolation and mosaicking for each radar, the mosaics can retain the high-quality observations and common observational characteristics of each radar. The fusion method of the S-POL and X-PAR radar mosaics simultaneously realizes the retention of the intensity distribution of the S-POL and the detailed features of the X-PAR. This method can utilize the observational advantages of the densely networked S-POL and X-PAR and obtain an accurate and detailed three-dimensional radar observation field.
In recent years, the X-band dual-polarization phased array weather radars (X-PAR) have been densely deployed in multiple regions across China, with the advantage of high spatiotemporal resolution. However, the data quality and limited coverage of single X-PAR are restricted factors of its application. Taking advantage of the radar network consist of the S-band dual-polarization weather radar (S-POL) and X-PAR, the research aims to obtain precise three-dimensional observation results. In this study, the data quality evaluation parameters were constructed for the radar variables of radars with different wavelengths to achieve the interpolation and mosaicking of single-wavelength radar networks. Furthermore, by calculating the deviations between the S-POL and X-PAR radar mosaics, the S-POL mosaic was taken as a background field with the low-resolution and credible characteristic, and integrate the observed detail structures from the X-PAR mosaic, the fusion of the S-POL and X-PAR radar mosaics was realized. The results show that by calculating the data quality evaluation parameters, combining the spatial distance from radar bins to grid points, and setting weights to perform interpolation and mosaicking for each radar, the mosaics can retain the high-quality observations and common observational characteristics of each radar. The fusion method of the S-POL and X-PAR radar mosaics simultaneously realizes the retention of the intensity distribution of the S-POL and the detailed features of the X-PAR. This method can utilize the observational advantages of the densely networked S-POL and X-PAR and obtain an accurate and detailed three-dimensional radar observation field.
Available online: August 14, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.081001
Abstract:
Our country has built the largest ground-based multi-band weather radar network in the world and successfully launched the first domestically-made and the third globally-made active radar precipitation measurement satellite. The overall technical level is world-class. Weather radars and precipitation satellites are important components of the integrated space-ground precipitation observation network and are key technical supports for accurately capturing precipitation dynamics and comprehensively analyzing precipitation characteristics. Ground-based weather radars have high temporal and spatial resolution, but their coverage is limited by geographical location and it is difficult to achieve continuous global observations. Spaceborne precipitation radars can provide three-dimensional precipitation structure information for the middle and low latitudes of the globe, especially for areas where ground equipment is difficult to cover, such as the ocean and plateaus. The integrated application of space-ground fusion achieves the organic combination of continuous early warning of large-scale precipitation situations and fine detection of local precipitation characteristics, providing more accurate and comprehensive data support and decision-making basis for meteorological forecasting, disaster warning, water resource management and other fields. This article details the technical characteristics, operational quality and data products of our country"s ground-based multi-band weather radar network and Fengyun-3 precipitation satellite, and from three aspects: the integration and application of passive microwave and active microwave of the main satellite and high-frequency infrared precipitation observation of the geostationary satellite, the simulation of ground radar signals based on geostationary satellite observation, and the comparison, verification and integration of spaceborne radar and ground-based radar observation data, puts forward preliminary thoughts and prospects for the collaborative observation and integrated application of space-ground precipitation radars in our country.
Our country has built the largest ground-based multi-band weather radar network in the world and successfully launched the first domestically-made and the third globally-made active radar precipitation measurement satellite. The overall technical level is world-class. Weather radars and precipitation satellites are important components of the integrated space-ground precipitation observation network and are key technical supports for accurately capturing precipitation dynamics and comprehensively analyzing precipitation characteristics. Ground-based weather radars have high temporal and spatial resolution, but their coverage is limited by geographical location and it is difficult to achieve continuous global observations. Spaceborne precipitation radars can provide three-dimensional precipitation structure information for the middle and low latitudes of the globe, especially for areas where ground equipment is difficult to cover, such as the ocean and plateaus. The integrated application of space-ground fusion achieves the organic combination of continuous early warning of large-scale precipitation situations and fine detection of local precipitation characteristics, providing more accurate and comprehensive data support and decision-making basis for meteorological forecasting, disaster warning, water resource management and other fields. This article details the technical characteristics, operational quality and data products of our country"s ground-based multi-band weather radar network and Fengyun-3 precipitation satellite, and from three aspects: the integration and application of passive microwave and active microwave of the main satellite and high-frequency infrared precipitation observation of the geostationary satellite, the simulation of ground radar signals based on geostationary satellite observation, and the comparison, verification and integration of spaceborne radar and ground-based radar observation data, puts forward preliminary thoughts and prospects for the collaborative observation and integrated application of space-ground precipitation radars in our country.
Technological Advances in National-Level Intelligent Digital Weather Forecasting Operational Systems
JIN Ronghua, CAO Yong, ZHAO Ruixia, DAI Kan, GUO Yunqian, XU Jun, ZENG Xiaoqing, WANG Yu, TANG Jian, WEI Qing
Available online: August 08, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.063003
Abstract:
Intelligent digital weather forecasting is a key means to support meteorological service. Countries around the world are actively developing new-generation seamless forecasting technology systems and promoting the application of artificial intelligence in the meteorological field. China has established a relatively complete intelligent digital weather forecasting operation system, achieving seamless forecasting for the near-surface and three-dimensional meteorological elements with a resolution of 1-km across the country and 5-km globally, covering a time range of 0-30 days. By developing adaptable technologies through the strategy of implementing different strategies at different time scales and integrating multi-source forecast, remarkable results have been achieved. A unified, standardized, and modularly expandable intelligent digital general technology framework has been constructed, constructing more than 30 types of algorithms and supporting "low-code" deployment, which plays an important role in major event support and extreme weather forecasting. The in-depth application of artificial intelligence technology has significantly improved forecasting performance in short-term and short-to-medium-term precipitation forecasting, severe convective weather forecasting, and disastrous gale forecasting by leveraging deep learning models. Progress has also been made in refined downscaling technology. At the same time, the data fusion and integration technology has continued to develop, and the intelligent integration of objective and subjective forecasting has developed to enhance the ability to forecast disastrous weather. China"s intelligent digital forecasting has improved the accuracy by 10% - 31% compared with the EC_IFS and CMA models and is widely applied in many fields. However, it still faces challenges. In the future, breakthroughs will be made in technologies related to the forecasting of disastrous and transitional weather, low-altitude hundreds-meter-resolution refined downscaling forecasting, industry-specific weather and risk forecasting, and the integrated platform with the meteorological "intelligent brain" as the core.
Intelligent digital weather forecasting is a key means to support meteorological service. Countries around the world are actively developing new-generation seamless forecasting technology systems and promoting the application of artificial intelligence in the meteorological field. China has established a relatively complete intelligent digital weather forecasting operation system, achieving seamless forecasting for the near-surface and three-dimensional meteorological elements with a resolution of 1-km across the country and 5-km globally, covering a time range of 0-30 days. By developing adaptable technologies through the strategy of implementing different strategies at different time scales and integrating multi-source forecast, remarkable results have been achieved. A unified, standardized, and modularly expandable intelligent digital general technology framework has been constructed, constructing more than 30 types of algorithms and supporting "low-code" deployment, which plays an important role in major event support and extreme weather forecasting. The in-depth application of artificial intelligence technology has significantly improved forecasting performance in short-term and short-to-medium-term precipitation forecasting, severe convective weather forecasting, and disastrous gale forecasting by leveraging deep learning models. Progress has also been made in refined downscaling technology. At the same time, the data fusion and integration technology has continued to develop, and the intelligent integration of objective and subjective forecasting has developed to enhance the ability to forecast disastrous weather. China"s intelligent digital forecasting has improved the accuracy by 10% - 31% compared with the EC_IFS and CMA models and is widely applied in many fields. However, it still faces challenges. In the future, breakthroughs will be made in technologies related to the forecasting of disastrous and transitional weather, low-altitude hundreds-meter-resolution refined downscaling forecasting, industry-specific weather and risk forecasting, and the integrated platform with the meteorological "intelligent brain" as the core.
Available online: August 07, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.080301
Abstract:
In this paper, a parallel chunking processing scheme is designed for the compression/decompression process by adopting OpenMP technology based on a conventional PC workstation as a benchmark, and the compression and decompression time of the data can be reduced to about 1/5 and 1/8 of the single-threaded one when the number of chunks reaches 16 under a 12-core/24-threaded CPU. For the decoding process, the results of parallel processing by PPI, radial and distance banks are compared, and it is found that the parallel processing scheme on radial is optimal, which can reduce the decoding time to about 1/8 of the single-threaded one. Through the application of the above two parallel optimization techniques, the pressure of radar base data in data transmission and preprocessing can be significantly reduced, and the data loading performance of the radar software can also be enhanced to improve the interactive experience of the radar analysis software based on base data.
In this paper, a parallel chunking processing scheme is designed for the compression/decompression process by adopting OpenMP technology based on a conventional PC workstation as a benchmark, and the compression and decompression time of the data can be reduced to about 1/5 and 1/8 of the single-threaded one when the number of chunks reaches 16 under a 12-core/24-threaded CPU. For the decoding process, the results of parallel processing by PPI, radial and distance banks are compared, and it is found that the parallel processing scheme on radial is optimal, which can reduce the decoding time to about 1/8 of the single-threaded one. Through the application of the above two parallel optimization techniques, the pressure of radar base data in data transmission and preprocessing can be significantly reduced, and the data loading performance of the radar software can also be enhanced to improve the interactive experience of the radar analysis software based on base data.
Available online: August 07, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.032401
Abstract:
This paper reviews the challenges in forecast services for major events in China over the past two decades. The main conclusions include: In conventional "fixed-time and fixed-location" weather element forecasting scenarios, the forecast challenges primarily focus on convection generation and dissipation or the occurrence of weak precipitation. Over short-term periods (12h or longer), the weather situation forecast provided by numerical models remains an important basis for decision-making, and the support from high-resolution numerical model products is indispensable. whereas in short-time or nowcasting, observational data and the comprehensive analytical capabilities of the forecasting team are more critical; In special "fixed-time and fixed-location" forecasting scenarios involving clouds, local winds, and local visibility, due to inadequate observational coverage, limited forecast capabilities of numerical models, and the lack of targeted objective forecasting methods at this stage, the forecast experience of the forecasting team, combined with observations and weather situation analysis, is crucial for successful service, especially in overseas on-site service support, regardless of whether it is short-time or nowcasting; With increased observational system coverage, improved accurate forecasting capabilities of numerical models, and the development of targeted objective forecasting methods including AI, special element forecasting scenarios will gradually transition into conventional element forecasting scenarios, and the leading role of the forecasting team will also gradually shift to short-time or nowcasting . To meet the meteorological support needs for various major events in the future, it is necessary to strengthen the construction of a three-dimensional full-element observation system, enhance the accurate forecasting capabilities of numerical models, promote the development of targeted objective forecasting technologies, and build a forecasting team with continuous self-learning, high generalization abilities, and strong communication skills.
This paper reviews the challenges in forecast services for major events in China over the past two decades. The main conclusions include: In conventional "fixed-time and fixed-location" weather element forecasting scenarios, the forecast challenges primarily focus on convection generation and dissipation or the occurrence of weak precipitation. Over short-term periods (12h or longer), the weather situation forecast provided by numerical models remains an important basis for decision-making, and the support from high-resolution numerical model products is indispensable. whereas in short-time or nowcasting, observational data and the comprehensive analytical capabilities of the forecasting team are more critical; In special "fixed-time and fixed-location" forecasting scenarios involving clouds, local winds, and local visibility, due to inadequate observational coverage, limited forecast capabilities of numerical models, and the lack of targeted objective forecasting methods at this stage, the forecast experience of the forecasting team, combined with observations and weather situation analysis, is crucial for successful service, especially in overseas on-site service support, regardless of whether it is short-time or nowcasting; With increased observational system coverage, improved accurate forecasting capabilities of numerical models, and the development of targeted objective forecasting methods including AI, special element forecasting scenarios will gradually transition into conventional element forecasting scenarios, and the leading role of the forecasting team will also gradually shift to short-time or nowcasting . To meet the meteorological support needs for various major events in the future, it is necessary to strengthen the construction of a three-dimensional full-element observation system, enhance the accurate forecasting capabilities of numerical models, promote the development of targeted objective forecasting technologies, and build a forecasting team with continuous self-learning, high generalization abilities, and strong communication skills.
Available online: July 27, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.062601
Abstract:
Taking into account the relationships between model temperature forecasts, model topography, observed temperatures, and actual topography, a dynamically approximated vertical rate correction method for the 2 m temperature that evolves over space and time has been designed. A correction experiment is conducted for Chongqing in 2023. Evaluation of ECMWF model forecasts show that the spatial distribution of forecast skill for maximum and minimum 2 m temperatures is similar, but forecast skill for maximum temperature is significantly worse than for minimum temperature. Additionally, forecast skill declines with increasing forecast lead time. A strong correlation is found between model topographic elevation bias and temperature forecast bias; areas with smaller elevation bias tend to exhibit better forecast skill, and vice versa. Comparative research reveals that the correction scheme based on dynamically approximated vertical rate significantly outperforms the scheme based on constant vertical rate. Both schemes improve the ECMWF model temperature forecasts, with better correction performance for maximum temperatures than for minimum temperatures. Compared to the raw model forecasts, the corrected results based on dynamically approximated vertical rate have increased the 10-day average forecast accuracy of maximum and minimum temperatures by 12.71% and 8.3%, respectively, and reduced the mean absolute error by 0.68°C and 0.3°C, respectively. The monthly average forecast accuracy of the maximum temperature for 24 h forecast lead time has increased by 20.34%. The minimum temperature has increased by 14.44% on average. Overall, the corrected temperature forecasts are more stable. The correction scheme based on dynamically approximated vertical rate can effectively reduce the temperature forecast bias. The greater the model topographic elevation bias, the smaller the amplitude of weather process fluctuations, and the more obvious the correction performance.
Taking into account the relationships between model temperature forecasts, model topography, observed temperatures, and actual topography, a dynamically approximated vertical rate correction method for the 2 m temperature that evolves over space and time has been designed. A correction experiment is conducted for Chongqing in 2023. Evaluation of ECMWF model forecasts show that the spatial distribution of forecast skill for maximum and minimum 2 m temperatures is similar, but forecast skill for maximum temperature is significantly worse than for minimum temperature. Additionally, forecast skill declines with increasing forecast lead time. A strong correlation is found between model topographic elevation bias and temperature forecast bias; areas with smaller elevation bias tend to exhibit better forecast skill, and vice versa. Comparative research reveals that the correction scheme based on dynamically approximated vertical rate significantly outperforms the scheme based on constant vertical rate. Both schemes improve the ECMWF model temperature forecasts, with better correction performance for maximum temperatures than for minimum temperatures. Compared to the raw model forecasts, the corrected results based on dynamically approximated vertical rate have increased the 10-day average forecast accuracy of maximum and minimum temperatures by 12.71% and 8.3%, respectively, and reduced the mean absolute error by 0.68°C and 0.3°C, respectively. The monthly average forecast accuracy of the maximum temperature for 24 h forecast lead time has increased by 20.34%. The minimum temperature has increased by 14.44% on average. Overall, the corrected temperature forecasts are more stable. The correction scheme based on dynamically approximated vertical rate can effectively reduce the temperature forecast bias. The greater the model topographic elevation bias, the smaller the amplitude of weather process fluctuations, and the more obvious the correction performance.
Available online: July 25, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.070802
Abstract:
Based on high-precision online atmospheric CO2 concentration measurements from the Shenyang Urban Ecosystem Station during June 2023 to May 2024, the REBS(Robust extraction of baseline signal) algorithm was employed to separate regional background and pollution data. The influence of regional transport on atmospheric CO2 concentrations in Shenyang was analyzed using surface wind field data and MeteoInfo statistical software. The contributions of fossil fuel combustion emissions and ecosystem emissions/absorption to CO2 concentrations were estimated according to carbon conservation principles. Results show that the average CO2 concentration at Shenyang Urban Ecosystem Station was 477.2 ppm, with background and pollution concentrations averaging 474.9 ppm and 519.4 ppm, respectively. High-concentration CO2 air masses affecting Shenyang originated from the southwest during spring and summer, and from northwest and southwest during winter. The potential CO2 emission source regions throughout the year were mainly distributed in most parts of Liaoning and Jilin provinces, southern Heilongjiang, eastern Inner Mongolia, Beijing-Tianjin-Hebei region, Shandong Peninsula, and the Yellow Sea and Bohai Sea areas. Compared to other seasons, fossil fuel combustion emissions contributed more significantly to Shenyang"s atmospheric CO2 concentrations during autumn and winter.
Based on high-precision online atmospheric CO2 concentration measurements from the Shenyang Urban Ecosystem Station during June 2023 to May 2024, the REBS(Robust extraction of baseline signal) algorithm was employed to separate regional background and pollution data. The influence of regional transport on atmospheric CO2 concentrations in Shenyang was analyzed using surface wind field data and MeteoInfo statistical software. The contributions of fossil fuel combustion emissions and ecosystem emissions/absorption to CO2 concentrations were estimated according to carbon conservation principles. Results show that the average CO2 concentration at Shenyang Urban Ecosystem Station was 477.2 ppm, with background and pollution concentrations averaging 474.9 ppm and 519.4 ppm, respectively. High-concentration CO2 air masses affecting Shenyang originated from the southwest during spring and summer, and from northwest and southwest during winter. The potential CO2 emission source regions throughout the year were mainly distributed in most parts of Liaoning and Jilin provinces, southern Heilongjiang, eastern Inner Mongolia, Beijing-Tianjin-Hebei region, Shandong Peninsula, and the Yellow Sea and Bohai Sea areas. Compared to other seasons, fossil fuel combustion emissions contributed more significantly to Shenyang"s atmospheric CO2 concentrations during autumn and winter.
Available online: July 23, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.060901
Abstract:
One of the key constraints on the difficulty of short-range forecasting of warm-season precipitation in the Beijing-Tianjin-Hebei region is the lack of atmospheric dynamic parameter profiles and the unknown pre-precipitation signal. In this study, we analyzed the evolution of the dynamical field before the trigger of strong convection by using the dynamical parameter profiles inverted from the wind profile radar (RWP) mesoscale network in the warm season (April-September) of 2023-2024 and constructed the horizontal convergence intensity index before the trigger of strong convection. The results show that, before the trigger convection, the dynamical field is characterized by a vertical upward motion configuration with low-level convergence and high-level divergence. During the 30 min before precipitation, the continuously enhanced convergent and upward motion favors the occurrence of strong convection. Among 763 strong precipitation events, the horizontal convergence intensity index was able to effectively identify the strong precipitation events with an identification accuracy of 72.4%. This study develops a quantitative discrimination technique of strong convective precursor signals from RWP mesoscale network, which provides an important reference for quantitatively analyzing the early warning of strong convection in the Beijing-Tianjin-Hebei region.
One of the key constraints on the difficulty of short-range forecasting of warm-season precipitation in the Beijing-Tianjin-Hebei region is the lack of atmospheric dynamic parameter profiles and the unknown pre-precipitation signal. In this study, we analyzed the evolution of the dynamical field before the trigger of strong convection by using the dynamical parameter profiles inverted from the wind profile radar (RWP) mesoscale network in the warm season (April-September) of 2023-2024 and constructed the horizontal convergence intensity index before the trigger of strong convection. The results show that, before the trigger convection, the dynamical field is characterized by a vertical upward motion configuration with low-level convergence and high-level divergence. During the 30 min before precipitation, the continuously enhanced convergent and upward motion favors the occurrence of strong convection. Among 763 strong precipitation events, the horizontal convergence intensity index was able to effectively identify the strong precipitation events with an identification accuracy of 72.4%. This study develops a quantitative discrimination technique of strong convective precursor signals from RWP mesoscale network, which provides an important reference for quantitatively analyzing the early warning of strong convection in the Beijing-Tianjin-Hebei region.
Available online: July 17, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.040301
Abstract:
In recent years, the interaction between aerosols and thunderstorm electrification had emerged as a focal point in academic research. Homogeneous nucleation of soluble aerosol droplets and heterogeneous nucleation of ice nuclei represent two primary mechanisms for ice crystal formation. The size and concentration of ice crystals in thunderstorms significantly influenced charge generation and distribution, which are critical factors in lightning occurrence. This study employed a three-dimensional thunderstorm model to investigate the impact of three distinct ice nucleation processes on lightning discharge characteristics, focused on a weak mountain thunderstorm case study. The results demonstrated that homogeneous nucleation generated a substantial number of ice crystals in the low-temperature region at the cloud top, resulting in prolonged discharge duration within the thunderstorm. The charge structure was predominantly dipolar, with a lower frequency of lightning, primarily consisting of cloud flashes originating from higher altitudes. In contrast, heterogeneous nucleation formed ice crystals in high-temperature regions, leading to an earlier charging process in thunderstorms. Ice crystals in these regions readily met charge reversal conditions, significantly increasing the negative non-inductive charging rate and favoring the formation of tripolar charge structures. Under these conditions, lightning occurred earlier and initiated from relatively lower altitudes, with heterogeneous nucleation facilitating lightning occurrence. When both homogeneous and heterogeneous nucleation processes occurred simultaneously, the thunderstorm charging process intensifies, resulting in a high lightning frequency. Furthermore, both nucleation processes advanced the initial lightning occurrence time and expanded the height range of the initial lightning trigger points. The tripolar charge structure promoted the occurrence of a substantial number of negative cloud-to-ground flashes.
In recent years, the interaction between aerosols and thunderstorm electrification had emerged as a focal point in academic research. Homogeneous nucleation of soluble aerosol droplets and heterogeneous nucleation of ice nuclei represent two primary mechanisms for ice crystal formation. The size and concentration of ice crystals in thunderstorms significantly influenced charge generation and distribution, which are critical factors in lightning occurrence. This study employed a three-dimensional thunderstorm model to investigate the impact of three distinct ice nucleation processes on lightning discharge characteristics, focused on a weak mountain thunderstorm case study. The results demonstrated that homogeneous nucleation generated a substantial number of ice crystals in the low-temperature region at the cloud top, resulting in prolonged discharge duration within the thunderstorm. The charge structure was predominantly dipolar, with a lower frequency of lightning, primarily consisting of cloud flashes originating from higher altitudes. In contrast, heterogeneous nucleation formed ice crystals in high-temperature regions, leading to an earlier charging process in thunderstorms. Ice crystals in these regions readily met charge reversal conditions, significantly increasing the negative non-inductive charging rate and favoring the formation of tripolar charge structures. Under these conditions, lightning occurred earlier and initiated from relatively lower altitudes, with heterogeneous nucleation facilitating lightning occurrence. When both homogeneous and heterogeneous nucleation processes occurred simultaneously, the thunderstorm charging process intensifies, resulting in a high lightning frequency. Furthermore, both nucleation processes advanced the initial lightning occurrence time and expanded the height range of the initial lightning trigger points. The tripolar charge structure promoted the occurrence of a substantial number of negative cloud-to-ground flashes.
Available online: July 14, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.071101
Abstract:
This paper proposes a deep learning model based on a sequential fusion encoder, which integrates the advantages of Convolutional Neural Networks (CNN), Convolutional Gated Recurrent Units (ConvGRU), and Transformer encoders, aiming to enhance the accuracy of winter precipitation phase prediction. Utilizing hourly precipitation weather phenomenon observational data from Wuhan over a 15-year period during winters from 2010 to 2024, as well as reanalysis data from the European Centre for Medium-Range Weather Forecasts, the model effectively addresses data imbalance issues through sample processing and data augmentation. Experimental results demonstrate superior performance in predicting solid precipitation, exhibiting high reliability in forecasting sleet and snow. By validating the model against complex weather processes in February 2024, its high precision in snowfall prediction is confirmed, though limitations are revealed in rapidly changing precipitation phases. This study offers an efficient and intelligent solution for deep learning-based prediction of winter precipitation phases, laying a foundation for further model optimization and enhanced predictive capabilities.
This paper proposes a deep learning model based on a sequential fusion encoder, which integrates the advantages of Convolutional Neural Networks (CNN), Convolutional Gated Recurrent Units (ConvGRU), and Transformer encoders, aiming to enhance the accuracy of winter precipitation phase prediction. Utilizing hourly precipitation weather phenomenon observational data from Wuhan over a 15-year period during winters from 2010 to 2024, as well as reanalysis data from the European Centre for Medium-Range Weather Forecasts, the model effectively addresses data imbalance issues through sample processing and data augmentation. Experimental results demonstrate superior performance in predicting solid precipitation, exhibiting high reliability in forecasting sleet and snow. By validating the model against complex weather processes in February 2024, its high precision in snowfall prediction is confirmed, though limitations are revealed in rapidly changing precipitation phases. This study offers an efficient and intelligent solution for deep learning-based prediction of winter precipitation phases, laying a foundation for further model optimization and enhanced predictive capabilities.
Available online: July 08, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.070501
Abstract:
This paper describes a quality control (QC) algorithm for reflectivity data of dual-channel millimeter-wave cloud radar (MMCR) in different regions.The data for the research from the 15 MMCR stations which were the first batch of MMCR to be approved for operational use in China.The algorithm provides a method for automatically identifying the QC threshold parameters for reflectivity(Z)and linear depolarization ratio (LDR), combined with filtering check and continuity check, etc., which can effectively eliminate non cloud and non rain echoes.The method is based on the distribution characteristics between the cloud or rain echoes and clutter in the MMCR data. It classifies and labels the cloud or rain echo and clutter samples from the 15 stations in 2023. Based on the intersection points of the frequency curves of the two types of echoes, the QC threshold parameters for reflectivity(Z)and linear depolarization ratio (LDR) for each station can gets rapidly. By comparing the correlation coefficient, average deviation and root mean square error of cloud heights calculated from the MMCR data before and after quality control and radiosonde data at different stations and during different observation periods.The effectiveness of the QC method is discussed.The results show that non-meteorological echoes in the data can be effectively removed after QC,especially low-level suspended clutter. The correlation coefficient with radiosonde-identified cloud base height increases from 0.47 to 0.91, and the correlation coefficient with cloud top height increases from 0.80 to 0.87. That improved that the calculated cloud heights after QC more reasonable. The data after QC can enhances the consistency between the cloud height data of MMCR and radiosonde.
This paper describes a quality control (QC) algorithm for reflectivity data of dual-channel millimeter-wave cloud radar (MMCR) in different regions.The data for the research from the 15 MMCR stations which were the first batch of MMCR to be approved for operational use in China.The algorithm provides a method for automatically identifying the QC threshold parameters for reflectivity(Z)and linear depolarization ratio (LDR), combined with filtering check and continuity check, etc., which can effectively eliminate non cloud and non rain echoes.The method is based on the distribution characteristics between the cloud or rain echoes and clutter in the MMCR data. It classifies and labels the cloud or rain echo and clutter samples from the 15 stations in 2023. Based on the intersection points of the frequency curves of the two types of echoes, the QC threshold parameters for reflectivity(Z)and linear depolarization ratio (LDR) for each station can gets rapidly. By comparing the correlation coefficient, average deviation and root mean square error of cloud heights calculated from the MMCR data before and after quality control and radiosonde data at different stations and during different observation periods.The effectiveness of the QC method is discussed.The results show that non-meteorological echoes in the data can be effectively removed after QC,especially low-level suspended clutter. The correlation coefficient with radiosonde-identified cloud base height increases from 0.47 to 0.91, and the correlation coefficient with cloud top height increases from 0.80 to 0.87. That improved that the calculated cloud heights after QC more reasonable. The data after QC can enhances the consistency between the cloud height data of MMCR and radiosonde.
Available online: June 20, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.011001
Abstract:
To obtain the X-band dual-polarization radar characteristics of hail in the southwestern Yunnan, a statistical analysis method was used to analyze 22 hail sample data detected by the Menglian X-band dual-polarization radar.The results show that hailstorm cells have the following characteristics:Maximum horizontal reflectivity factor (ZH) ≥58 dBz;The 45 dBz echo development height (H45) ≥7.1 km, with a height difference between H45 and the wet-bulb 0℃ level ≥3.3 km;86% of hail cells have H45 exceeding the height of the -20°C layer;The 50 dBz echo development height (H50) ≥5.7 km, with a height difference between H50 and the -20℃ level ranging from -1.2 to 2.7 km;Vertical integrated liquid water content (VIL) density ≥2.8 g·m-3, and the VIL increased by 4.7–18.3 kg·m-2 in the volume scan preceding hailfall.Differential reflectivity (ZDR) and specific differential phase (KDP) average and median values, above 0℃ layer, concentrated near 0 value, predominantly negative; below 0℃layer within 1 km, transition from negative to positive values, gradually increasing with height decrease, maximum in the near-surface layer, reaching approximately 1.5 dB and 0.7 °/km respectively. The range of values for each parameter above the 0℃ layer, ZDR -1.92 to 1.35 dB, KDP -1.97 to 1.29 °/km, correlation coefficient (CC) 0.86 to 0.99; below the 0℃ layer, ZDR -1.92 to 3.74 dB, KDP -2.98 to 2.66 °/km, CC 0.79 to 0.98.The research results provide a reference for the detection and identification of hail characteristics by the X-band dual-polarization radar in the southwestern Yunnan region.
To obtain the X-band dual-polarization radar characteristics of hail in the southwestern Yunnan, a statistical analysis method was used to analyze 22 hail sample data detected by the Menglian X-band dual-polarization radar.The results show that hailstorm cells have the following characteristics:Maximum horizontal reflectivity factor (ZH) ≥58 dBz;The 45 dBz echo development height (H45) ≥7.1 km, with a height difference between H45 and the wet-bulb 0℃ level ≥3.3 km;86% of hail cells have H45 exceeding the height of the -20°C layer;The 50 dBz echo development height (H50) ≥5.7 km, with a height difference between H50 and the -20℃ level ranging from -1.2 to 2.7 km;Vertical integrated liquid water content (VIL) density ≥2.8 g·m-3, and the VIL increased by 4.7–18.3 kg·m-2 in the volume scan preceding hailfall.Differential reflectivity (ZDR) and specific differential phase (KDP) average and median values, above 0℃ layer, concentrated near 0 value, predominantly negative; below 0℃layer within 1 km, transition from negative to positive values, gradually increasing with height decrease, maximum in the near-surface layer, reaching approximately 1.5 dB and 0.7 °/km respectively. The range of values for each parameter above the 0℃ layer, ZDR -1.92 to 1.35 dB, KDP -1.97 to 1.29 °/km, correlation coefficient (CC) 0.86 to 0.99; below the 0℃ layer, ZDR -1.92 to 3.74 dB, KDP -2.98 to 2.66 °/km, CC 0.79 to 0.98.The research results provide a reference for the detection and identification of hail characteristics by the X-band dual-polarization radar in the southwestern Yunnan region.
Available online: June 13, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.011302
Abstract:
Based on the complete monthly reports of the maximum and minimum temperatures recorded by instruments since the establishment of the Guiyang National Reference Meteorological Station on September 5, 1920, the sequences of the maximum and minimum temperatures and the daily temperature differences over the past century in Guiyang were established. Through multiple methods of verification of the sequences, it was found that the minimum temperature and the daily temperature differences from 1938 to 1944 had significant differences from the mean value of the sequences, and there were breakpoints in the sequences in 1937, 1944 and 2000. According to the historical evolution, observation record books and weather report stubs, as well as the comparison of multi-source and multi-station data, the minimum and maximum temperatures from 1938 to 1944 in the reports were found to be inaccurate, thus the data for this period were replaced with the records from the observation record books. Using the mean value of daily maximum and minimum temperatures and the daily temperature differences from 1938 to 1949, a conversion and correction scale was established to construct the daily temperatures for the period from 1921 to 1936 when there were no records. The non-uniformity of temperature caused by station relocation was revised recursively by using the initial values of this station and the annual changes of the optimal reference station. The final established homogenized temperature series of Guiyang over the past century shows a good consistency with the global temperature changes during the same period. The results show that over the past century, Guiyang"s temperature has experienced two relatively significant "warming", one from 1937 to 1953 and the other one starting from 1978, the current warming accelerated in 1996 and changed abruptly in 2011. The tendency rate of temperature change in Guiyang over the past century is 0.122℃ per decade to 0.136℃ per decade, and the minimum temperature has been oscillating upward since 1929, warming up with a tendency rate of 0.26℃ per decade to 0.31℃ per decade. The daily temperature differences decreases with a tendency rate of -0.27℃ per decade to -0.29℃ per decade. There is no obvious trend change in the maximum temperature. The warming rate of temperature and minimum temperature in autumn and winter is higher than that in spring and summer, February is the month of most warming, and July is the month of least warming. The warming is mainly caused by the increase in minimum temperature.
Based on the complete monthly reports of the maximum and minimum temperatures recorded by instruments since the establishment of the Guiyang National Reference Meteorological Station on September 5, 1920, the sequences of the maximum and minimum temperatures and the daily temperature differences over the past century in Guiyang were established. Through multiple methods of verification of the sequences, it was found that the minimum temperature and the daily temperature differences from 1938 to 1944 had significant differences from the mean value of the sequences, and there were breakpoints in the sequences in 1937, 1944 and 2000. According to the historical evolution, observation record books and weather report stubs, as well as the comparison of multi-source and multi-station data, the minimum and maximum temperatures from 1938 to 1944 in the reports were found to be inaccurate, thus the data for this period were replaced with the records from the observation record books. Using the mean value of daily maximum and minimum temperatures and the daily temperature differences from 1938 to 1949, a conversion and correction scale was established to construct the daily temperatures for the period from 1921 to 1936 when there were no records. The non-uniformity of temperature caused by station relocation was revised recursively by using the initial values of this station and the annual changes of the optimal reference station. The final established homogenized temperature series of Guiyang over the past century shows a good consistency with the global temperature changes during the same period. The results show that over the past century, Guiyang"s temperature has experienced two relatively significant "warming", one from 1937 to 1953 and the other one starting from 1978, the current warming accelerated in 1996 and changed abruptly in 2011. The tendency rate of temperature change in Guiyang over the past century is 0.122℃ per decade to 0.136℃ per decade, and the minimum temperature has been oscillating upward since 1929, warming up with a tendency rate of 0.26℃ per decade to 0.31℃ per decade. The daily temperature differences decreases with a tendency rate of -0.27℃ per decade to -0.29℃ per decade. There is no obvious trend change in the maximum temperature. The warming rate of temperature and minimum temperature in autumn and winter is higher than that in spring and summer, February is the month of most warming, and July is the month of least warming. The warming is mainly caused by the increase in minimum temperature.
Available online: May 29, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.051901
Abstract:
Multiple DSG5 raindrop distrometers are utilized to analyze the raindrop size distribution of the residual vortex of Typhoon Haikui (2311) in the Pearl River Delta and evaluate the performance of different QPE algorithms in the S/X bands. The results indicate that the impact of the residual vortex of Haikui on rainfall in the Pearl River Delta can be divided into two main stages. The first stage is primarily influenced by the convergence of the southwest monsoon and easterly airflow on the eastern side of the vortex itself, with a deep moisture convergence layer. The microphysical processes of rainfall are relatively uniform with relatively small mass-weighted mean diameter (Dm) and higher normalized intercept parameter (lgNw), i.e., smaller particle sizes and higher number concentrations of raindrops. The second stage is characterized by intense rainfall caused by the convergence of southerly winds in the boundary layer on the outskirts of the residual vortex, with shallower moisture convergence layer. The rainfall particles are more dispersed, with more rainfall events featuring large Dm and low lgNw rain drops. Overall, medium-sized raindrops make a?major contribution to the total rainfall amount, but as rainfall intensity increases, the contribution of extremely large raindrops to rain rate at the second stage is significantly higher than that at the first stage. The dual-polarization parameters derived from raindrop size distribution of this process shows that, under the same rain rate (R), horizontal reflectivity factor (Zh), specific differential phase (KDP), and differential reflectivity (ZDR) at the first stage are smaller than those at the second stage. The deviation of QPE algorithms in the S/X bands calculated based on distrometers data shows that, R(Zh) has relatively large biases in both the S-band and X-band, while the bias of R(Zh, ZDR) is relatively small in the S-band but increases significantly with increasing rain rate in the X-band and R(KDP) has better performance in the X-band . R(KDP, ZDR) performs the best in both the S/X band and is minimally affected by changes in raindrop size distribution, with little difference between the two stages.
Multiple DSG5 raindrop distrometers are utilized to analyze the raindrop size distribution of the residual vortex of Typhoon Haikui (2311) in the Pearl River Delta and evaluate the performance of different QPE algorithms in the S/X bands. The results indicate that the impact of the residual vortex of Haikui on rainfall in the Pearl River Delta can be divided into two main stages. The first stage is primarily influenced by the convergence of the southwest monsoon and easterly airflow on the eastern side of the vortex itself, with a deep moisture convergence layer. The microphysical processes of rainfall are relatively uniform with relatively small mass-weighted mean diameter (Dm) and higher normalized intercept parameter (lgNw), i.e., smaller particle sizes and higher number concentrations of raindrops. The second stage is characterized by intense rainfall caused by the convergence of southerly winds in the boundary layer on the outskirts of the residual vortex, with shallower moisture convergence layer. The rainfall particles are more dispersed, with more rainfall events featuring large Dm and low lgNw rain drops. Overall, medium-sized raindrops make a?major contribution to the total rainfall amount, but as rainfall intensity increases, the contribution of extremely large raindrops to rain rate at the second stage is significantly higher than that at the first stage. The dual-polarization parameters derived from raindrop size distribution of this process shows that, under the same rain rate (R), horizontal reflectivity factor (Zh), specific differential phase (KDP), and differential reflectivity (ZDR) at the first stage are smaller than those at the second stage. The deviation of QPE algorithms in the S/X bands calculated based on distrometers data shows that, R(Zh) has relatively large biases in both the S-band and X-band, while the bias of R(Zh, ZDR) is relatively small in the S-band but increases significantly with increasing rain rate in the X-band and R(KDP) has better performance in the X-band . R(KDP, ZDR) performs the best in both the S/X band and is minimally affected by changes in raindrop size distribution, with little difference between the two stages.
Available online: May 28, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.040401
Abstract:
Due to the limitations of the limited area, lateral boundary perturbations are one of the primary perturbation methods for regional ensemble prediction. However, it remains unclear how to construct lateral boundary perturbations for the high-resolution regional ensemble prediction system of the China Meteorological Administration (CMA) to improve forecast skill. This paper develops a mixed lateral boundary perturbation method using the perturbation field of the CMA global ensemble prediction and lateral boundary field of the regional deterministic model, and adjusts the perturbation magnitude through dynamic perturbation coefficients. The results showed that the absence of lateral boundary perturbations suppresses the growth of perturbation energy at later forecast ranges, leading to insufficient ensemble spreads. The mixed lateral boundary perturbation scheme can enhance the perturbation energy spectra at meso-α and large scales, as well as improve the spread-skill relationships and probabilistic forecast skills for isobaric element and precipitation. Compared to the mixed lateral boundary perturbation scheme, the dynamic mixed lateral boundary perturbation scheme can enhance the spectral energy above 100 km, improve the spread-skill relationships, as well as the probabilistic forecast skills for low-level variables and precipitation beyond 24 hours, exhibiting good potential for operational application.
Due to the limitations of the limited area, lateral boundary perturbations are one of the primary perturbation methods for regional ensemble prediction. However, it remains unclear how to construct lateral boundary perturbations for the high-resolution regional ensemble prediction system of the China Meteorological Administration (CMA) to improve forecast skill. This paper develops a mixed lateral boundary perturbation method using the perturbation field of the CMA global ensemble prediction and lateral boundary field of the regional deterministic model, and adjusts the perturbation magnitude through dynamic perturbation coefficients. The results showed that the absence of lateral boundary perturbations suppresses the growth of perturbation energy at later forecast ranges, leading to insufficient ensemble spreads. The mixed lateral boundary perturbation scheme can enhance the perturbation energy spectra at meso-α and large scales, as well as improve the spread-skill relationships and probabilistic forecast skills for isobaric element and precipitation. Compared to the mixed lateral boundary perturbation scheme, the dynamic mixed lateral boundary perturbation scheme can enhance the spectral energy above 100 km, improve the spread-skill relationships, as well as the probabilistic forecast skills for low-level variables and precipitation beyond 24 hours, exhibiting good potential for operational application.
Available online: May 14, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.031002
Abstract:
A localized severe convective rainfall event over eastern Sichuan basin under the background of southwest vortex on 8 August 2021 was analyzed by using the Chongqing S-band dual-pol radar, ERA5 reanalysis data and CMPAS multi-source precipitation product. The results are as follow: At the early development of convection, radar observed some relative weak convective characteristics. Snow particles play a major role in ice-phase particles at middle-upper level. The proportion of drizzle identification ranges from 20% to 40%, raindrops’ size and surface rain rate are both small. During the rapid intensification, radar measurements increased rapidly as well. ZDR and KDP columns can extend well above 8 km. Uplifted droplet generates supercooled water which facilitate ice-phase process over the melting layer. Melting of descending ice hydrometeors lead to the enhancement of liquid particles’ size and concentration at low level, which intensified the surface rain rate. Convective cells were merged with each other and shift eastward subsequently. As the system weakened, dry and wet snow particles become the main component of ice-phase at middle-upper level again. Both size and number of liquid particles at middle-lower level are decreased and surface rainrate gets weakened accordingly. Dual-pol variables and hydrometeor identification can basically exhibit the characteristic of hydrometeor transformation within the convective systems and cohere reasonably with the variation of surface rain rate.
A localized severe convective rainfall event over eastern Sichuan basin under the background of southwest vortex on 8 August 2021 was analyzed by using the Chongqing S-band dual-pol radar, ERA5 reanalysis data and CMPAS multi-source precipitation product. The results are as follow: At the early development of convection, radar observed some relative weak convective characteristics. Snow particles play a major role in ice-phase particles at middle-upper level. The proportion of drizzle identification ranges from 20% to 40%, raindrops’ size and surface rain rate are both small. During the rapid intensification, radar measurements increased rapidly as well. ZDR and KDP columns can extend well above 8 km. Uplifted droplet generates supercooled water which facilitate ice-phase process over the melting layer. Melting of descending ice hydrometeors lead to the enhancement of liquid particles’ size and concentration at low level, which intensified the surface rain rate. Convective cells were merged with each other and shift eastward subsequently. As the system weakened, dry and wet snow particles become the main component of ice-phase at middle-upper level again. Both size and number of liquid particles at middle-lower level are decreased and surface rainrate gets weakened accordingly. Dual-pol variables and hydrometeor identification can basically exhibit the characteristic of hydrometeor transformation within the convective systems and cohere reasonably with the variation of surface rain rate.
Available online: May 06, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.041802
Abstract:
Based on the China Meteorological Administration (CMA) convection-permitting ensemble prediction system (CMA-CPEPS) and regional ensemble prediction system (CMA-REPS), the precipitation forecasting performance during the 2023 flood season (from 15 June to 28 August) in China, and a case analysis of July 2023 severe torrential rain in North China was objectively and comprehensively evaluated. The results indicate that CMA-REPS has an issue with systematically overestimating precipitation forecasts, CMA-CPEPS has significantly improved this problem. Compared to CMA-REPS, CMA-CPEPS shows significantly superiority in predictive capacity for weather changes and its temporal changes, with better probability forecasting and resolution ability of precipitation. Both CMA-CPEPS and CMA-REPS exhibit low spread values, while spread/RMSE value and the spatial correlation between spread and RMSE of CMA-CPEPS and CMA-REPS are equivalent. In the July 2023 severe torrential rain in North China, CMA-CPEPS has better ability to capture precipitation details compared to CMA-REPS. CMA-CPEPS outperforms in forecasting precipitation intensity, the evolution trend of precipitation intensity, and spatio-temporal resolution of heavy precipitation, especially in short-duration heavy precipitation events. Overall, CMA-CPEPS represents a significantly enhancement over CMA-REPS in precipitation forecasting for the 2023 flood season in China.
Based on the China Meteorological Administration (CMA) convection-permitting ensemble prediction system (CMA-CPEPS) and regional ensemble prediction system (CMA-REPS), the precipitation forecasting performance during the 2023 flood season (from 15 June to 28 August) in China, and a case analysis of July 2023 severe torrential rain in North China was objectively and comprehensively evaluated. The results indicate that CMA-REPS has an issue with systematically overestimating precipitation forecasts, CMA-CPEPS has significantly improved this problem. Compared to CMA-REPS, CMA-CPEPS shows significantly superiority in predictive capacity for weather changes and its temporal changes, with better probability forecasting and resolution ability of precipitation. Both CMA-CPEPS and CMA-REPS exhibit low spread values, while spread/RMSE value and the spatial correlation between spread and RMSE of CMA-CPEPS and CMA-REPS are equivalent. In the July 2023 severe torrential rain in North China, CMA-CPEPS has better ability to capture precipitation details compared to CMA-REPS. CMA-CPEPS outperforms in forecasting precipitation intensity, the evolution trend of precipitation intensity, and spatio-temporal resolution of heavy precipitation, especially in short-duration heavy precipitation events. Overall, CMA-CPEPS represents a significantly enhancement over CMA-REPS in precipitation forecasting for the 2023 flood season in China.
Available online: April 28, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.040601
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Abstract: Abstract: Based on observation data and ballistic theory, a simple model was established to analyze the influence of atmospheric vertical structure on the weather modification rocket ballistic performance during the ascending phase. The results indicate that the intensity and direction of the horizontal wind field have significant impact on ballistic performance, especially in low level wind fields below 1000m height. The impact of air density was relatively small. The model could be beneficial for ballistic correction, include ballistic height, deflection, and distance. It would provide relatively accurate prediction trajectory of weather modification rocket.
Abstract: Abstract: Based on observation data and ballistic theory, a simple model was established to analyze the influence of atmospheric vertical structure on the weather modification rocket ballistic performance during the ascending phase. The results indicate that the intensity and direction of the horizontal wind field have significant impact on ballistic performance, especially in low level wind fields below 1000m height. The impact of air density was relatively small. The model could be beneficial for ballistic correction, include ballistic height, deflection, and distance. It would provide relatively accurate prediction trajectory of weather modification rocket.
Available online: April 18, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.041801
Abstract:
The study of drought in the water source and receiving areas of the middle route project of South-to-North Water Diversion Project is of great significance for the water resource scheduling and operation management of the project. Based on the NCEP-NCAR reanalysis data and the daily average temperature, precipitation, and meteorological drought composite index of all meteorological stations in the water source and receiving areas of middle route project of South to North Water Diversion Project from 1961 to 2023, this article conducts identification and evaluation of regional drought processes in water source area and water receiving area. The results show that the annual values of drought days in the water source area and water receiving area are 101 days and 114 days, respectively, showing an overall spatial distribution characteristic of "more in the middle and less at both ends". The northern part of Henan and the southern part of Hebei in the water receiving area are high-value areas for drought days. The number of drought days in most of the water source areas, most of the water receiving areas in Henan, and eastern Hebei is increasing, while the number of drought days in most of the water receiving areas in northern, western, and southern Hebei, Beijing, and Tianjin is decreasing. Using the dynamic regional drought process identification method, a total of 97 regional drought processes have been identified in the study area since 1961. Using the percentile method to divide the intensity index of regional drought processes, threshold values corresponding to different intensity levels are obtained, and a total of 4 "extremely strong", 15 "strong", 30 "relatively strong", and 48 "moderate" regional drought processes occur in the study area. The strongest three regional drought processes occurred in 1968, 2001, and 1997, and the differences in circulation characteristics led to significant differences in the spatial and temporal distribution of drought days and the proportion of drought stations at different levels among the three processes. Among the 97 regional drought processes in the study area, 54.6% are caused by drought in the water source area but not in the water receiving area, which is beneficial for engineering water diversion. At the same time, in some years, the entire region is uniformly dry or the water source area is dry while the water receiving area is not dry, which is not conducive to engineering water diversion. Therefore, water resource scheduling of the middle route project of South-to-North Water Diversion Project needs to carry out targeted water diversion work based on the actual situation.
The study of drought in the water source and receiving areas of the middle route project of South-to-North Water Diversion Project is of great significance for the water resource scheduling and operation management of the project. Based on the NCEP-NCAR reanalysis data and the daily average temperature, precipitation, and meteorological drought composite index of all meteorological stations in the water source and receiving areas of middle route project of South to North Water Diversion Project from 1961 to 2023, this article conducts identification and evaluation of regional drought processes in water source area and water receiving area. The results show that the annual values of drought days in the water source area and water receiving area are 101 days and 114 days, respectively, showing an overall spatial distribution characteristic of "more in the middle and less at both ends". The northern part of Henan and the southern part of Hebei in the water receiving area are high-value areas for drought days. The number of drought days in most of the water source areas, most of the water receiving areas in Henan, and eastern Hebei is increasing, while the number of drought days in most of the water receiving areas in northern, western, and southern Hebei, Beijing, and Tianjin is decreasing. Using the dynamic regional drought process identification method, a total of 97 regional drought processes have been identified in the study area since 1961. Using the percentile method to divide the intensity index of regional drought processes, threshold values corresponding to different intensity levels are obtained, and a total of 4 "extremely strong", 15 "strong", 30 "relatively strong", and 48 "moderate" regional drought processes occur in the study area. The strongest three regional drought processes occurred in 1968, 2001, and 1997, and the differences in circulation characteristics led to significant differences in the spatial and temporal distribution of drought days and the proportion of drought stations at different levels among the three processes. Among the 97 regional drought processes in the study area, 54.6% are caused by drought in the water source area but not in the water receiving area, which is beneficial for engineering water diversion. At the same time, in some years, the entire region is uniformly dry or the water source area is dry while the water receiving area is not dry, which is not conducive to engineering water diversion. Therefore, water resource scheduling of the middle route project of South-to-North Water Diversion Project needs to carry out targeted water diversion work based on the actual situation.
Available online: April 17, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.041601
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Based on the monthly rainfall of 643 stations in China, NCEP reanalysis data and NOAA ERSST sea surface temperature data from 1961 to 2023, impacts of early and late onset of El Ni?o on summer precipitation in China are analyzed. The results are as followed. Westerly wind anomalies in the equatorial west-central Pacific are more pronounced in June-August of years with early El Ni?o onset than in years with late El Ni?o onset, resulting in a more obvious warming of the sea surface temperature in the equatorial east-central Pacific in earlier onset years, the sea surface temperature in the quarter continues to rise. However, the positive anomaly of sea surface temperature in the equatorial east-central Pacific Ocean in the later onset years is not obvious and changes slowly. There is obvious differences in summer precipitation in central and eastern China between the El Ni?o earlier onset years and the El Ni?o later onset years, especially in July and August. In the El Ni?o earlier onset years, the Western North Pacific anticyclone (WNPAC) generally appears around August, the summer precipitation in central and eastern China is distributed in "-+-" from south to north, with more precipitation than normal in Jianghuai Region, and less precipitation than normal in other areas. In June, the Western Pacific Ocean is an abnormal cyclone, the precipitation in most of China’s central and eastern parts is less than normal. In July, the abnormal cyclone in the Western Pacific Ocean retreats southward significantly, the precipitation in regions of the Jiangnan, Northwest and North China continues to be less than normal. And the abnormal anticyclone to the east of Japan significantly extends westward and presses southward, the southeast coastal areas of China turns to abnormal southerly winds, leading to precipitation along the southern China coast, Jianghuai basin turn to more than normal. In August, Northwest Pacific Ocean turns into an anomalous anticyclone, WNPAC begins to appear, the precipitation over the middle and lower reaches of the Yangtze River and most parts of its south is more than normal, while the precipitation in most parts of northern China is less than normal. In the later onset years, WNPAC usually appears in October or later, the Western Pacific Ocean has been an abnormal cyclone from June to August. The summer precipitation in the central and eastern regions of China is distributed in "+-+" from south to north, and the precipitation persistence characteristics of each month are obvious.
Based on the monthly rainfall of 643 stations in China, NCEP reanalysis data and NOAA ERSST sea surface temperature data from 1961 to 2023, impacts of early and late onset of El Ni?o on summer precipitation in China are analyzed. The results are as followed. Westerly wind anomalies in the equatorial west-central Pacific are more pronounced in June-August of years with early El Ni?o onset than in years with late El Ni?o onset, resulting in a more obvious warming of the sea surface temperature in the equatorial east-central Pacific in earlier onset years, the sea surface temperature in the quarter continues to rise. However, the positive anomaly of sea surface temperature in the equatorial east-central Pacific Ocean in the later onset years is not obvious and changes slowly. There is obvious differences in summer precipitation in central and eastern China between the El Ni?o earlier onset years and the El Ni?o later onset years, especially in July and August. In the El Ni?o earlier onset years, the Western North Pacific anticyclone (WNPAC) generally appears around August, the summer precipitation in central and eastern China is distributed in "-+-" from south to north, with more precipitation than normal in Jianghuai Region, and less precipitation than normal in other areas. In June, the Western Pacific Ocean is an abnormal cyclone, the precipitation in most of China’s central and eastern parts is less than normal. In July, the abnormal cyclone in the Western Pacific Ocean retreats southward significantly, the precipitation in regions of the Jiangnan, Northwest and North China continues to be less than normal. And the abnormal anticyclone to the east of Japan significantly extends westward and presses southward, the southeast coastal areas of China turns to abnormal southerly winds, leading to precipitation along the southern China coast, Jianghuai basin turn to more than normal. In August, Northwest Pacific Ocean turns into an anomalous anticyclone, WNPAC begins to appear, the precipitation over the middle and lower reaches of the Yangtze River and most parts of its south is more than normal, while the precipitation in most parts of northern China is less than normal. In the later onset years, WNPAC usually appears in October or later, the Western Pacific Ocean has been an abnormal cyclone from June to August. The summer precipitation in the central and eastern regions of China is distributed in "+-+" from south to north, and the precipitation persistence characteristics of each month are obvious.
Available online: April 15, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.031001
Abstract:
Based on conventional observation data, Doppler weather radar data and ERA5 reanalysis data, the physical process responsible for the enhancement and maintenance of a strong squall line affecting the Bohai Sea area during the night of July 31, 2021 was analyzed. The results show that coastal terrain and sea surface temperature were key factors affecting the intensity of squall lines. The warm water areas in the central and western Bohai Sea exhibited favorable conditions for thermal instability, and the areas with high wind speeds corresponded to the areas with high sea surface temperatures. The horn-shaped coastal terrain around the Bohai Bay exhibited the "narrow tube effect", resulting in significant wind field convergence on the windward side of the coast, which was conducive to the triggering of convection. In the early stage, the cold pool outflow formed by multi-cell storms on land converged with environmental airflow, causing the storms to propagate eastward and move into the sea. The non-uniform onshore winds caused by the complex coastal terrain of the Bohai Bay were conducive to the formation of new coastal thunderstorms. These thunderstorms merged and strengthened, ultimately evolving into squall lines. The mesoscale vortices formed by the cold pool outflow of squall lines and the environmental airflow along the northern coast of Bohai Bay promoted the propagation and strengthening of squall lines along the coastline. The development of coastal convection led to the spread of cold density towards the sea, which strengthened the intensity of the sea surface cold pool and was conducive to the development of offshore squall lines. In the process of strengthening squall lines over the sea, boundary layer frontogenesis played a crucial role. Compared with the cold pool effect, the influence of boundary layer temperature and environmental airflow was more significant, ultimately leading to the development and strengthening of squall lines in the warm water area of the Bohai Sea and their weakening and dissipation in the cold water area.
Based on conventional observation data, Doppler weather radar data and ERA5 reanalysis data, the physical process responsible for the enhancement and maintenance of a strong squall line affecting the Bohai Sea area during the night of July 31, 2021 was analyzed. The results show that coastal terrain and sea surface temperature were key factors affecting the intensity of squall lines. The warm water areas in the central and western Bohai Sea exhibited favorable conditions for thermal instability, and the areas with high wind speeds corresponded to the areas with high sea surface temperatures. The horn-shaped coastal terrain around the Bohai Bay exhibited the "narrow tube effect", resulting in significant wind field convergence on the windward side of the coast, which was conducive to the triggering of convection. In the early stage, the cold pool outflow formed by multi-cell storms on land converged with environmental airflow, causing the storms to propagate eastward and move into the sea. The non-uniform onshore winds caused by the complex coastal terrain of the Bohai Bay were conducive to the formation of new coastal thunderstorms. These thunderstorms merged and strengthened, ultimately evolving into squall lines. The mesoscale vortices formed by the cold pool outflow of squall lines and the environmental airflow along the northern coast of Bohai Bay promoted the propagation and strengthening of squall lines along the coastline. The development of coastal convection led to the spread of cold density towards the sea, which strengthened the intensity of the sea surface cold pool and was conducive to the development of offshore squall lines. In the process of strengthening squall lines over the sea, boundary layer frontogenesis played a crucial role. Compared with the cold pool effect, the influence of boundary layer temperature and environmental airflow was more significant, ultimately leading to the development and strengthening of squall lines in the warm water area of the Bohai Sea and their weakening and dissipation in the cold water area.
Available online: April 11, 2025 , DOI: 10.7519/j.issn.1000-0526.2024.122601
Abstract:
From 29 to 30 June 2023, a local abrupt torrential rainstorm occurred in the western region of Hunan Province, but the forecasters and numerical models both failed to forecast the rainfall intensity. Based on conventional surface and upper-air observation data, Doppler radar and FY-4A data, ERA5 reanalysis data and numerical forecast products, the mesoscale characteristics and forecast difficulties of this heavy rainfall event were analyzed. The results show that this is a severe torrential rain process under the background of the northwest airflow behind the upper-level trough. The northwest airflow drives the cold air behind the northeast cold vortex to the south, and merges with the southwester warm-humid air flows strengthened at night, which leads to the occurrence of this process. The severe torrential rain is caused by a back-building and quasi-stationary meso-α-scale convective system ( MCS ), which is composed of several strongly developing γ-scale MCSs. On the doppler radar image, the MCS shows as an organized linear echo band, and the echo belongs to the warm cloud precipitation echo of low centroid and high rainfall efficiency. Under the favorable environmental background, the long-term maintenance of the boundary layer convergence line，the wind velocity pulsation of the low-level jet and the vertical structure of low-level convergence and high-level divergence lead to the initiation and organization of the convective cells, the consolidation strengthening, backward propagation of MCS and convective cell train effect are important reasons for the severe torrential rains. The significant deviations in the subjective forecast of short-term timeliness was possibly caused by the forecasting deviation of the lower troposphere dynamic and thermal fields of the numerical models, the deficiency of forecaster"s ability to correct the model forecast and the uncertainty of the heavy rainstorm forecast increased by the complex topography in western Hunan.. Therefore, it is very crucial for forecasters to use the automatic weather station data, satellite data and radar data with high spatiotemporal resolutions to analyze the changes of the mesoscale environmental conditions, strengthen the short-term nowcasting, and issue early warning signals in time.
From 29 to 30 June 2023, a local abrupt torrential rainstorm occurred in the western region of Hunan Province, but the forecasters and numerical models both failed to forecast the rainfall intensity. Based on conventional surface and upper-air observation data, Doppler radar and FY-4A data, ERA5 reanalysis data and numerical forecast products, the mesoscale characteristics and forecast difficulties of this heavy rainfall event were analyzed. The results show that this is a severe torrential rain process under the background of the northwest airflow behind the upper-level trough. The northwest airflow drives the cold air behind the northeast cold vortex to the south, and merges with the southwester warm-humid air flows strengthened at night, which leads to the occurrence of this process. The severe torrential rain is caused by a back-building and quasi-stationary meso-α-scale convective system ( MCS ), which is composed of several strongly developing γ-scale MCSs. On the doppler radar image, the MCS shows as an organized linear echo band, and the echo belongs to the warm cloud precipitation echo of low centroid and high rainfall efficiency. Under the favorable environmental background, the long-term maintenance of the boundary layer convergence line，the wind velocity pulsation of the low-level jet and the vertical structure of low-level convergence and high-level divergence lead to the initiation and organization of the convective cells, the consolidation strengthening, backward propagation of MCS and convective cell train effect are important reasons for the severe torrential rains. The significant deviations in the subjective forecast of short-term timeliness was possibly caused by the forecasting deviation of the lower troposphere dynamic and thermal fields of the numerical models, the deficiency of forecaster"s ability to correct the model forecast and the uncertainty of the heavy rainstorm forecast increased by the complex topography in western Hunan.. Therefore, it is very crucial for forecasters to use the automatic weather station data, satellite data and radar data with high spatiotemporal resolutions to analyze the changes of the mesoscale environmental conditions, strengthen the short-term nowcasting, and issue early warning signals in time.
Available online: April 01, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.012402
Abstract:
A warm sector severe convective event dominated by short-term heavy precipitation occurred in southern Anhui early in the morning of 27 May, 2023. The train effect formed by a number of north-south trend parallel meso-β scale short convections caused more than 100 mm sudden local heavy precipitation in 2 hours. The numerical simulation of this event was carried out by using WRF-EnKF, a rapid update assimilation system for service operation in Anhui Meteorological Observatory. The results show that (1) the interaction between large-scale environmental field and mesoscale convective system results in the increase of horizontal scale and intensification of several short convections. In terms of dynamic action, after the occurrence of convection, a meso-γ scale cyclonic vortex formed between the short convection and the low level jet core, causing the development of eastward convection. Meanwhile, the surface convergence line formed between the outflow of thunderstorm and the environmental wind triggers new convection in the south side of the short convection, making continuously development linearly to the south for the short convection. In terms of environmental conditions, multiple parallel low level jet cores provide favorable dynamic and thermal conditions for the development of convection. Inverse secondary circulation in the middle and upper levels occurred by the strong development of convection leads to the significant enhancement of atmospheric instability on the south side and the development of convection leads to the strengthen of deep vertical wind shear. (2) The interaction between the convections causes the maintenance of the short convection structure. Parallel convection forms parallel thunderstorm high pressure, and the interaction between the outflow of adjacent thunderstorms leads to the formation of multiple parallel positive and negative divergence pairs, thus bringing about multiple parallel zonal-vertical circulations between adjacent convections in the vertical direction. This is conducive to the maintenance and development of the structure of multiple short convections.
A warm sector severe convective event dominated by short-term heavy precipitation occurred in southern Anhui early in the morning of 27 May, 2023. The train effect formed by a number of north-south trend parallel meso-β scale short convections caused more than 100 mm sudden local heavy precipitation in 2 hours. The numerical simulation of this event was carried out by using WRF-EnKF, a rapid update assimilation system for service operation in Anhui Meteorological Observatory. The results show that (1) the interaction between large-scale environmental field and mesoscale convective system results in the increase of horizontal scale and intensification of several short convections. In terms of dynamic action, after the occurrence of convection, a meso-γ scale cyclonic vortex formed between the short convection and the low level jet core, causing the development of eastward convection. Meanwhile, the surface convergence line formed between the outflow of thunderstorm and the environmental wind triggers new convection in the south side of the short convection, making continuously development linearly to the south for the short convection. In terms of environmental conditions, multiple parallel low level jet cores provide favorable dynamic and thermal conditions for the development of convection. Inverse secondary circulation in the middle and upper levels occurred by the strong development of convection leads to the significant enhancement of atmospheric instability on the south side and the development of convection leads to the strengthen of deep vertical wind shear. (2) The interaction between the convections causes the maintenance of the short convection structure. Parallel convection forms parallel thunderstorm high pressure, and the interaction between the outflow of adjacent thunderstorms leads to the formation of multiple parallel positive and negative divergence pairs, thus bringing about multiple parallel zonal-vertical circulations between adjacent convections in the vertical direction. This is conducive to the maintenance and development of the structure of multiple short convections.
Available online: March 11, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.022601
Abstract:
A cumuliform cloud with supercooled water is the condition required for the icing test flight, which is referred to as supercooled cumuliform cloud in this paper. On the basis of the cloud phase state, cloud classification and liquid water top height data from CloudSat-CALIPSO cloud products and the air temperature from ERA5 reanalysis data, focusing on the local solar afternoon data with good interannual continuity, the historical supercooled cloud sample data over China from 2006-2019 were derived, and the spatiotemporal distribution characteristics of supercooled cumuliform clouds were analyzed. The supercooled cumuliform clouds in China most occur in the eastern part of the Qinghai?Xizang Plateau and extend to central China via the Yunnan–Guizhou–Sichuan region, with an annual average occurrence frequency of 0.4. The high value areas of supercooled cumuliform clouds are more westward than that of supercooled stratiform cloud and the occurrence frequency is higher. The occurrence frequencies of the four types of supercooled cumuliform clouds in descending order were as follows: altocumulus over Southwest China, Central China, and East China; stratocumulus over the plateau and the eastern sea surface; cumulus over the southern side of the plateau; and deep convection over Yunnan, Central China, and the southeast land and sea. In winter, there are three high-value centers over Sichuan, Guizhou, the ocean over eastern China, and the Sea of Japan, while the high-value center in summer extends from the eastern part of the Qinghai–Xizang Plateau to other locations on the plateau and the surrounding mountainous areas. In addition, the interannual variation of supercooled cumuliform clouds showed significant increasing trends in January in central China, the west of Northwest China and the west of the Qinghai-Xizang Plateau.
A cumuliform cloud with supercooled water is the condition required for the icing test flight, which is referred to as supercooled cumuliform cloud in this paper. On the basis of the cloud phase state, cloud classification and liquid water top height data from CloudSat-CALIPSO cloud products and the air temperature from ERA5 reanalysis data, focusing on the local solar afternoon data with good interannual continuity, the historical supercooled cloud sample data over China from 2006-2019 were derived, and the spatiotemporal distribution characteristics of supercooled cumuliform clouds were analyzed. The supercooled cumuliform clouds in China most occur in the eastern part of the Qinghai?Xizang Plateau and extend to central China via the Yunnan–Guizhou–Sichuan region, with an annual average occurrence frequency of 0.4. The high value areas of supercooled cumuliform clouds are more westward than that of supercooled stratiform cloud and the occurrence frequency is higher. The occurrence frequencies of the four types of supercooled cumuliform clouds in descending order were as follows: altocumulus over Southwest China, Central China, and East China; stratocumulus over the plateau and the eastern sea surface; cumulus over the southern side of the plateau; and deep convection over Yunnan, Central China, and the southeast land and sea. In winter, there are three high-value centers over Sichuan, Guizhou, the ocean over eastern China, and the Sea of Japan, while the high-value center in summer extends from the eastern part of the Qinghai–Xizang Plateau to other locations on the plateau and the surrounding mountainous areas. In addition, the interannual variation of supercooled cumuliform clouds showed significant increasing trends in January in central China, the west of Northwest China and the west of the Qinghai-Xizang Plateau.
Available online: February 18, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.011603
Abstract:
On August 13, 2022, a local severe convection occurred near the coast of Shanghai under the control of Western Pacific subtropical high. This event displayed characteristics of a short life span, strong local manifestation, and high intensity. Using data from minute-level ground automatic weather stations, FY-4A geostationary meteorological satellite visible light cloud images, and dual-polarization radar reflectivity factor, a study was conducted on the short-range forecasting techniques and causes of this local strong convection, employing diagnostic variables such as Q vector, perturbation dew point temperature and perturbation temperature. The findings are as follows:(1) The occurrence of precipitation at the ground level was identified as the sign of local strong convective events. By analyzing radar reflectivity factor, satellite visible light cloud images, and Q vector divergence combined with perturbation dew point temperature and perturbation temperature data from ground automatic weather stations, advanced warnings of the convective event could be issued 23, 70, and 100 minutes in advance, respectively. This integrated monitoring and mutual verification of the atmospheric, satellite, and ground observations not only improved the lead time of early warnings for local severe convection but also reduced missed detections. (2) Under the control of the Western Pacific subtropical high-pressure system, temperatures exceeding 35 ℃, combined with the perturbations in temperature and dew point near the urban area, provided favorable thermodynamic conditions for the initiation of deep convection. Simultaneously, differences in land and water underlying characteristics led to higher temperatures on urban land compared to the adjacent Yangtze River water, generating onshore winds. On one hand, this process experienced abrupt changes in land-water underlying characteristics and complex urban land surfaces, causing convergence of wind direction and speed. On the other hand, the convergence of warm and cold air led to atmospheric instability, providing favorable local dynamic forcing conditions. (3) Further analysis reveals that the appearance of significant Q vector divergence convergence at the surface, persisting until surface precipitation occurs, indicates the generation of vertical upward motion due to the dynamic and thermal forcing at the surface. Furthermore, the interaction between the sea breeze front and the convergence-induced updrafts from the urban heat island results in local severe convection.
On August 13, 2022, a local severe convection occurred near the coast of Shanghai under the control of Western Pacific subtropical high. This event displayed characteristics of a short life span, strong local manifestation, and high intensity. Using data from minute-level ground automatic weather stations, FY-4A geostationary meteorological satellite visible light cloud images, and dual-polarization radar reflectivity factor, a study was conducted on the short-range forecasting techniques and causes of this local strong convection, employing diagnostic variables such as Q vector, perturbation dew point temperature and perturbation temperature. The findings are as follows:(1) The occurrence of precipitation at the ground level was identified as the sign of local strong convective events. By analyzing radar reflectivity factor, satellite visible light cloud images, and Q vector divergence combined with perturbation dew point temperature and perturbation temperature data from ground automatic weather stations, advanced warnings of the convective event could be issued 23, 70, and 100 minutes in advance, respectively. This integrated monitoring and mutual verification of the atmospheric, satellite, and ground observations not only improved the lead time of early warnings for local severe convection but also reduced missed detections. (2) Under the control of the Western Pacific subtropical high-pressure system, temperatures exceeding 35 ℃, combined with the perturbations in temperature and dew point near the urban area, provided favorable thermodynamic conditions for the initiation of deep convection. Simultaneously, differences in land and water underlying characteristics led to higher temperatures on urban land compared to the adjacent Yangtze River water, generating onshore winds. On one hand, this process experienced abrupt changes in land-water underlying characteristics and complex urban land surfaces, causing convergence of wind direction and speed. On the other hand, the convergence of warm and cold air led to atmospheric instability, providing favorable local dynamic forcing conditions. (3) Further analysis reveals that the appearance of significant Q vector divergence convergence at the surface, persisting until surface precipitation occurs, indicates the generation of vertical upward motion due to the dynamic and thermal forcing at the surface. Furthermore, the interaction between the sea breeze front and the convergence-induced updrafts from the urban heat island results in local severe convection.
Available online: January 06, 2025 , DOI: 10.7519/j.issn.1000-0526.2024.123001
Abstract:
This study examines the multi-scale processes responsible for an extreme thunderstorm downburst event (peak wind 31.5 m·s-1) that occurred at Tianjin Airport on 4 August 2013, focusing on the synoptic background, structural characteristics of the storm, and dynamical mechanisms of the severe winds. The results show that this event developed within a post-trough unstable environment, characterized by a pronounced dry layer in the mid-troposphere and moisture concentration below 925 hPa. Convective available potential energy (CAPE) exceeding 3000 J·kg-1, coupled with strong 0-6 km vertical wind shear and steep temperature lapse rates in the boundary layer, established a favorable environment for thunderstorm gales. The damaging winds originated from a squall line propagating rapidly from northwest to southeast. The passage of its leading gust front triggered the initial wind surge, while subsequent extreme winds during the second phase resulted from a downburst generated by an intensifying multi-cell storm embedded in the squall line. Both the squall line and downburst exhibited significant mobility, with precipitation-induced evaporative cooling, hydrometeor loading, and mid-level convergence identified as primary drivers of downburst formation.
This study examines the multi-scale processes responsible for an extreme thunderstorm downburst event (peak wind 31.5 m·s-1) that occurred at Tianjin Airport on 4 August 2013, focusing on the synoptic background, structural characteristics of the storm, and dynamical mechanisms of the severe winds. The results show that this event developed within a post-trough unstable environment, characterized by a pronounced dry layer in the mid-troposphere and moisture concentration below 925 hPa. Convective available potential energy (CAPE) exceeding 3000 J·kg-1, coupled with strong 0-6 km vertical wind shear and steep temperature lapse rates in the boundary layer, established a favorable environment for thunderstorm gales. The damaging winds originated from a squall line propagating rapidly from northwest to southeast. The passage of its leading gust front triggered the initial wind surge, while subsequent extreme winds during the second phase resulted from a downburst generated by an intensifying multi-cell storm embedded in the squall line. Both the squall line and downburst exhibited significant mobility, with precipitation-induced evaporative cooling, hydrometeor loading, and mid-level convergence identified as primary drivers of downburst formation.
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2012,38(12):1482-1491, DOI: 10.7519/j.issn.1000-0526.2012.12.005
Abstract:
By using the conventional meteorological data, Doppler radar data and NCEP/NCAR reanalysis data, the characteristics of Doppler radar’s reflectivity, environmental condition and trigger mechanism of the heavy rain are analyzed and compared between two abrupt heavy rain processes occurring in Sichuan Basin on 3 July (7.3) and 23 July (7.23) 2011. The results show that: the “7.3” heavy rain happened under a typical circulation background, and moisture transporting to the heavy rain area from the South China Sea was smoothly, thus the heavy rainfall maintained so long, but the “7.23” heavy rain occurred behind the upper cold vortex, and convective unstable energy was abundant and vertical wind shear was strong, thus this heavy rain process happened with hail and thunderstorm weather accompanied, its radar reflectivity was 5 dBz stronger than “7.3” case and had the characteristics of severe storms such as the low level weak reflectivity and the upper echo overhang. As a whole, the non equilibrium force is contributed to the occurrence of heavy rain and it is the excited mechanism of the two heavy rainfalls, and the change of the divergence evolvement is consistent with the strength and the position of the heavy rain which would happen 6 hours later．
By using the conventional meteorological data, Doppler radar data and NCEP/NCAR reanalysis data, the characteristics of Doppler radar’s reflectivity, environmental condition and trigger mechanism of the heavy rain are analyzed and compared between two abrupt heavy rain processes occurring in Sichuan Basin on 3 July (7.3) and 23 July (7.23) 2011. The results show that: the “7.3” heavy rain happened under a typical circulation background, and moisture transporting to the heavy rain area from the South China Sea was smoothly, thus the heavy rainfall maintained so long, but the “7.23” heavy rain occurred behind the upper cold vortex, and convective unstable energy was abundant and vertical wind shear was strong, thus this heavy rain process happened with hail and thunderstorm weather accompanied, its radar reflectivity was 5 dBz stronger than “7.3” case and had the characteristics of severe storms such as the low level weak reflectivity and the upper echo overhang. As a whole, the non equilibrium force is contributed to the occurrence of heavy rain and it is the excited mechanism of the two heavy rainfalls, and the change of the divergence evolvement is consistent with the strength and the position of the heavy rain which would happen 6 hours later．
2017,43(7):769-780, DOI: 10.7519/j.issn.1000-0526.2017.07.001
Abstract:
The spatial distributions of severe convective wind (SCW) and nonsevere thunderstorms (NT) over South China, occurring between 08:00 BT and 20:00 BT during spring and summer in 2010-2014, were analyzed by using the observational data from China Meteorological Administration. And then, their environmental characteristics were compared between SCW and NT in spring and summer. It was found that SCW in summer is more frequently than that in spring and that NT in summer is about 3.6 times the counts of NT in spring. SCW events mainly concentrate in the western Guangdong to the Pearl River Delta Region. Compared to NT, SCW is generally associated with stronger baroclinity, instability and stronger dynamic forcing. The precipitable water and averaged relative humidity between 700-500 hPa of SCW tend to be higher than those of NT in spring, while the opposite is the case for the pattern in summer. In conclusion, it is obvious that the dynamic forcing for SCW in spring is much better than these in summer, while the thermal condition is more significant in summer.
The spatial distributions of severe convective wind (SCW) and nonsevere thunderstorms (NT) over South China, occurring between 08:00 BT and 20:00 BT during spring and summer in 2010-2014, were analyzed by using the observational data from China Meteorological Administration. And then, their environmental characteristics were compared between SCW and NT in spring and summer. It was found that SCW in summer is more frequently than that in spring and that NT in summer is about 3.6 times the counts of NT in spring. SCW events mainly concentrate in the western Guangdong to the Pearl River Delta Region. Compared to NT, SCW is generally associated with stronger baroclinity, instability and stronger dynamic forcing. The precipitable water and averaged relative humidity between 700-500 hPa of SCW tend to be higher than those of NT in spring, while the opposite is the case for the pattern in summer. In conclusion, it is obvious that the dynamic forcing for SCW in spring is much better than these in summer, while the thermal condition is more significant in summer.
2010,36(3):9-18, DOI: 10.7519/j.issn.1000-0526.2010.3.002
Abstract:
Potential vorticity (PV) is one of the important concepts in advanced synoptic and dynamic meteorology. This paper is a brief introduction to the theory of potential vorticity, including the concept of PV, the conservation and invertibility of PV, PV thinking, moist PV (MPV), and the application of PV theory.
Potential vorticity (PV) is one of the important concepts in advanced synoptic and dynamic meteorology. This paper is a brief introduction to the theory of potential vorticity, including the concept of PV, the conservation and invertibility of PV, PV thinking, moist PV (MPV), and the application of PV theory.
FU Jiaolan, MA Xuekuan, CHEN Tao, ZHANG Fang, ZHANG Xidi, SUN Jun, QUAN Wanqing, YANG Shunan, SHEN Xiaolin
2017,43(5):528-539, DOI: 10.7519/j.issn.1000-0526.2017.05.002
Abstract:
An extremely severe precipitation event took place in North China in 19-20 July 2016. It was characterized by large rainfall, persistent rainfall, warm cloud rainfall, strong local rainfall intensity and orographic precipitation. Its rainfall was larger than that of the extreme rainfall in 3-5 August 1996, and only next to the amount of the 2-7 August 1963 extreme rainfall event. It occurred under the circulation background of the South Asia high moving eastward, the West Pacific subtropical high moving northwestward and the low vortex in the westerlies developing in mid high latitude. The abnormal development of Huanghuai cyclone, southwest and southeast low level jets, and the abnormally abundant moisture indicates that the dynamic lifting and moisture conditions favored this severe rainfall process significantly. The whole rainfall event presented clearly the phase characteristics, and could be divided into two stages. The first stage was the orographic rainfall caused by the easterly winds ahead of the trough from the early morning to the daytime of 19 July, while the second part was produced by spiral rain bands in the north side of Huanghuai cyclone from the night of 19 to the daytime of 20 July. In the first stage, the easterly low level jet was lifted by the Taihang Mountains, which continuously triggered the convective cells along the east edge of the mountains. The weak dry and cold advection at mid level and the strong warm and wet advection at low level jointly maintained the convective instability. The cold pool generated by heavy rainfall and the mesoscale frontogenesis process created by local orographic effect provided favorable conditions for severe convections to occur continuously. The second stage rainfall was mainly related to the development of cut off vortex and Huanghuai cyclone. The blocking of the high pressure system slowed the steps of Huanghuai cyclone in North China, thus leading to the long lasting rainfall process.
An extremely severe precipitation event took place in North China in 19-20 July 2016. It was characterized by large rainfall, persistent rainfall, warm cloud rainfall, strong local rainfall intensity and orographic precipitation. Its rainfall was larger than that of the extreme rainfall in 3-5 August 1996, and only next to the amount of the 2-7 August 1963 extreme rainfall event. It occurred under the circulation background of the South Asia high moving eastward, the West Pacific subtropical high moving northwestward and the low vortex in the westerlies developing in mid high latitude. The abnormal development of Huanghuai cyclone, southwest and southeast low level jets, and the abnormally abundant moisture indicates that the dynamic lifting and moisture conditions favored this severe rainfall process significantly. The whole rainfall event presented clearly the phase characteristics, and could be divided into two stages. The first stage was the orographic rainfall caused by the easterly winds ahead of the trough from the early morning to the daytime of 19 July, while the second part was produced by spiral rain bands in the north side of Huanghuai cyclone from the night of 19 to the daytime of 20 July. In the first stage, the easterly low level jet was lifted by the Taihang Mountains, which continuously triggered the convective cells along the east edge of the mountains. The weak dry and cold advection at mid level and the strong warm and wet advection at low level jointly maintained the convective instability. The cold pool generated by heavy rainfall and the mesoscale frontogenesis process created by local orographic effect provided favorable conditions for severe convections to occur continuously. The second stage rainfall was mainly related to the development of cut off vortex and Huanghuai cyclone. The blocking of the high pressure system slowed the steps of Huanghuai cyclone in North China, thus leading to the long lasting rainfall process.
2006,32(10):64-69, DOI: 10.7519/j.issn.1000-0526.2006.10.010
Abstract:
Based on the data of CINRAD Doppler Radar which located at Xinle of Hebei Province,the hail,strong wind and heavy rainfall weather events in mid-south Hebei in 2004 are statistically analyzed.The routine radar products,such as echo reflectivity,radial velocity,Vertically Integrated Liquid(VIL)Water,hail index,mesocyclone,velocity azimuth display wind profile,etc.are used in this statistics.The results show that hail's VIL value is larger than generic thunder storm's.At the same time,greater VIL value and longer sustaining will bring about greater diameter hail and larger effect area.It is the very useful index to indicate strong wind in mesocyclone products and the wind direction sudden change in radial velocity products.A reference based on analyzing this type synoptic forecast with radar system in future is proposed.
Based on the data of CINRAD Doppler Radar which located at Xinle of Hebei Province,the hail,strong wind and heavy rainfall weather events in mid-south Hebei in 2004 are statistically analyzed.The routine radar products,such as echo reflectivity,radial velocity,Vertically Integrated Liquid(VIL)Water,hail index,mesocyclone,velocity azimuth display wind profile,etc.are used in this statistics.The results show that hail's VIL value is larger than generic thunder storm's.At the same time,greater VIL value and longer sustaining will bring about greater diameter hail and larger effect area.It is the very useful index to indicate strong wind in mesocyclone products and the wind direction sudden change in radial velocity products.A reference based on analyzing this type synoptic forecast with radar system in future is proposed.
Zhou Yuquan, Chen Yingying, Li Juan, Huang Yimei, He Xiaodong, Zhou Feifei, Wu Menxin, Hu Bo, Mao Jietai
2008,34(12):27-35, DOI: 10.7519/j.issn.1000-0526.2008.12.004
Abstract:
Cloud macro and micro physical characteristic parameters play an important role not only in the field of the analysis and forecast of the weather and climate, but also in the field of weather modification to identify the seeding c ondition. Based on the data from FY-2C/D stationary satellite and SBDART radiati on transfer model, associated with the sounding data and surface information, a method retrieving cloud macro and micro physical parameters is established in th is research. These parameters include cloud top height, cloud top temperature, d epth of super-cooled layer, depth of warm layer, cloud bottom height, depth of c loud, cloud optical thickness, cloud effective particle radius and cloud liquid water content. It has been run operationally. In this paper, the correlated info rmation such as physical meaning, retrieving method and technology, retrieving p rocess and data format are simply introduced. Furthermore, comparing with the ob servation of Cloudsat up to the minute, the retrieving results of main cloud par ameters are proved to be reasonable and usable. By contrast with same kind produ cts of MODIS, it also shows good corresponding relationship.
Cloud macro and micro physical characteristic parameters play an important role not only in the field of the analysis and forecast of the weather and climate, but also in the field of weather modification to identify the seeding c ondition. Based on the data from FY-2C/D stationary satellite and SBDART radiati on transfer model, associated with the sounding data and surface information, a method retrieving cloud macro and micro physical parameters is established in th is research. These parameters include cloud top height, cloud top temperature, d epth of super-cooled layer, depth of warm layer, cloud bottom height, depth of c loud, cloud optical thickness, cloud effective particle radius and cloud liquid water content. It has been run operationally. In this paper, the correlated info rmation such as physical meaning, retrieving method and technology, retrieving p rocess and data format are simply introduced. Furthermore, comparing with the ob servation of Cloudsat up to the minute, the retrieving results of main cloud par ameters are proved to be reasonable and usable. By contrast with same kind produ cts of MODIS, it also shows good corresponding relationship.
2012,38(10):1255-1266, DOI: 10.7519/j.issn.1000-0526.2012.10.012
Abstract:
Precipitation characteristics, environment conditions, generation and development of the mesoscale convective system that brought about the extreme torrential rain in Beijing on 21 July 2012 were analyzed comprehensively in this paper by using various conventional and unconventional data. The results showed that the extreme torrential rain had the characteristics of long duration, great rainfall and wide coverage area and its process consisted of warm area precipitation and frontal precipitation. The warm area rainfall started earlier, the severe precipitation center was scattered and lasted long while the frontal rainfallprocess contained several severe rainfall centers with high precipitation efficiency, lasting a short time.Environment conditions of the mesoscale convective system that triggered this extreme severe rainfall were analyzed. The results showed that interactions of high level divergence, the wind shear and convergence with the vortex in the lower troposphere and the surface wind convergence line provided favorable environment to the severe extreme rain. The warm humid airs from the tropical and sub tropical zones converged over the torrential rain region, continuous and sufficient water vapor manifested as high atmospheric column of precipitable water and strong low level water vapor convergence and other extreme vapor conditions for the torrential rain. In addition, the intense precipitation was triggered by the vortex wind shear, wind disturbance on low level jet, surface wind convergence line and the effect of terrain under the condition of the plentiful water vapour and maintained. With the cold front moved eastward, heavy frontal rainfall was brought by the development and evolution of convective system made by the cold air and the suitable vertical wind shear.Generation and development processes of the mesoscale convective system were also studied. The findings suggested that stratiform cloud precipitation and dispersed convective precipitation occurred firstly in the precipitation process. The warm and steady stratiform cloud precipitation changed to be highly organized convectional precipitation as the cold dry air invaded. Many small scale and mesoscale convective clusters developed into mesoscale convective complex (MCC), leading to the extreme severe precipitation. Since all the directions of the echo long axis, terrain and echo movement were parallel, train effect was obviously seen in the radar echo imegery during this precipitation process. Meanwhile, the radar echo had the characteristics of backward propagation and low centroid which was similar to tropical heavy rainfalls. Finally, a series of scientific problems were proposed according to the integrated analysis on the observation data of this rare torrential rain event, such as the causes for the extreme torrential rain and the extreme rich water vapor, mechanisms for the warm area torrential rain in the north of China, the mechanism for the train effect and backward propagation, mechanisms for the organization and maintenance of the convective cells, the simulation and analysis ability of the numerical models to extreme torrential rains and so on.
Precipitation characteristics, environment conditions, generation and development of the mesoscale convective system that brought about the extreme torrential rain in Beijing on 21 July 2012 were analyzed comprehensively in this paper by using various conventional and unconventional data. The results showed that the extreme torrential rain had the characteristics of long duration, great rainfall and wide coverage area and its process consisted of warm area precipitation and frontal precipitation. The warm area rainfall started earlier, the severe precipitation center was scattered and lasted long while the frontal rainfallprocess contained several severe rainfall centers with high precipitation efficiency, lasting a short time.Environment conditions of the mesoscale convective system that triggered this extreme severe rainfall were analyzed. The results showed that interactions of high level divergence, the wind shear and convergence with the vortex in the lower troposphere and the surface wind convergence line provided favorable environment to the severe extreme rain. The warm humid airs from the tropical and sub tropical zones converged over the torrential rain region, continuous and sufficient water vapor manifested as high atmospheric column of precipitable water and strong low level water vapor convergence and other extreme vapor conditions for the torrential rain. In addition, the intense precipitation was triggered by the vortex wind shear, wind disturbance on low level jet, surface wind convergence line and the effect of terrain under the condition of the plentiful water vapour and maintained. With the cold front moved eastward, heavy frontal rainfall was brought by the development and evolution of convective system made by the cold air and the suitable vertical wind shear.Generation and development processes of the mesoscale convective system were also studied. The findings suggested that stratiform cloud precipitation and dispersed convective precipitation occurred firstly in the precipitation process. The warm and steady stratiform cloud precipitation changed to be highly organized convectional precipitation as the cold dry air invaded. Many small scale and mesoscale convective clusters developed into mesoscale convective complex (MCC), leading to the extreme severe precipitation. Since all the directions of the echo long axis, terrain and echo movement were parallel, train effect was obviously seen in the radar echo imegery during this precipitation process. Meanwhile, the radar echo had the characteristics of backward propagation and low centroid which was similar to tropical heavy rainfalls. Finally, a series of scientific problems were proposed according to the integrated analysis on the observation data of this rare torrential rain event, such as the causes for the extreme torrential rain and the extreme rich water vapor, mechanisms for the warm area torrential rain in the north of China, the mechanism for the train effect and backward propagation, mechanisms for the organization and maintenance of the convective cells, the simulation and analysis ability of the numerical models to extreme torrential rains and so on.
2013,39(10):1284-1292, DOI: 10.7519/j.issn.1000-0526.2013.10.006
Abstract:
Based on the fog observation data during 24-27 December 2006 (advection radiation fog), NCEP NC reanalysis data (2.5°×2.5°) and GDAS global meteorological data (1°×1°), detailed trajectory analysis of the boundary layer characteristics and water vapor transport of the fog is investigated, combined with the weather condition, meteorological elements and physical quantity field. The results show that: (1) there is thick inversion layer, even multi layer inversion throughout the dense fog event. Temperatures of different inversion tops in the middle and high levels are 2-5℃ higher than the surface temperature. The thickness of inversion layer is more than 200 m, and it gets to 500 m at 08:00 BT 26 December, indicating the atmosphere is very stable and conducive to the convergence of water vapor before the fog forms. However, it is not favorable for the divergence of water vapor after the formation of fog, which helps the development and maintenance of the fog, causing the fog to last about 64 hours with dense fog (visibility <50 m) about 37 hours; (2) The divergence of water vapor flux in low level is negative in the advection fog event. The upper air has persistent moisture convergence and the strongest moisture convergence appears at 02:00 BT 25 December, being -30×10-7 g·s-1·cm-2·hPa-1. The accumulation of low level water vapor makes fog form and develop while the divergence of water vapor flux speeds up its dissipation. 〖JP2〗The long lasting advection radiation fog is mainly caused by the continuous water vapor convergence; (3) The water vapor path is from the coastal area in easten China to Nanjing. The water vapor is continuously supplied from sea during the fog event, with the water vapor flux maximum getting to 2 g·s-1·hPa-1·cm-1. The sufficient supply and supplementary of water vapor determines the duration of the fog.
Based on the fog observation data during 24-27 December 2006 (advection radiation fog), NCEP NC reanalysis data (2.5°×2.5°) and GDAS global meteorological data (1°×1°), detailed trajectory analysis of the boundary layer characteristics and water vapor transport of the fog is investigated, combined with the weather condition, meteorological elements and physical quantity field. The results show that: (1) there is thick inversion layer, even multi layer inversion throughout the dense fog event. Temperatures of different inversion tops in the middle and high levels are 2-5℃ higher than the surface temperature. The thickness of inversion layer is more than 200 m, and it gets to 500 m at 08:00 BT 26 December, indicating the atmosphere is very stable and conducive to the convergence of water vapor before the fog forms. However, it is not favorable for the divergence of water vapor after the formation of fog, which helps the development and maintenance of the fog, causing the fog to last about 64 hours with dense fog (visibility <50 m) about 37 hours; (2) The divergence of water vapor flux in low level is negative in the advection fog event. The upper air has persistent moisture convergence and the strongest moisture convergence appears at 02:00 BT 25 December, being -30×10-7 g·s-1·cm-2·hPa-1. The accumulation of low level water vapor makes fog form and develop while the divergence of water vapor flux speeds up its dissipation. 〖JP2〗The long lasting advection radiation fog is mainly caused by the continuous water vapor convergence; (3) The water vapor path is from the coastal area in easten China to Nanjing. The water vapor is continuously supplied from sea during the fog event, with the water vapor flux maximum getting to 2 g·s-1·hPa-1·cm-1. The sufficient supply and supplementary of water vapor determines the duration of the fog.
ZHANG Xiaoling, ZHANG Tao, LIU Xinhua, ZHOU Qingliang, CHEN Yun, ZHOU Xiaoxia, ZHENG Yongguang, ZHAO Surong
2010,36(7):143-150, DOI: 10.7519/j.issn.1000-0526.2010.7.021
Abstract:
Mesoscale severe weather forecasting ability is limited, in some sense for a lack of valid analysis on mesoscale convective systems and its favorable environments. This paper introduces the mesoscale weather chart analysis techniq ue which was tested in the National Meteorological Center (NMC). Mesoscale weath er chart analyzes the favorable environmental conditions of mesoscale convective systems based on observational data and numerical weather forecast outputs. It includes upper air composite chart and surface chart. In the upper air composite ch art, by analyzing wind, temperature, moisture, temperature change and height change, the diagnostic systems and features in all the lower, middle and upper t roposphere isobaric layers are combined into one plot, which can clearly displa y the available environments and synoptic pattern of severe convective weather. In the surface chart, the analysis contents are pressure, wind, temperature, moi sture, convective weather phenomena and all kinds of boundaries (fronts). The te st in NMC shows that mesoscale weather chart analysis is a dependable means for severe convective weather outlook forecasting.
Mesoscale severe weather forecasting ability is limited, in some sense for a lack of valid analysis on mesoscale convective systems and its favorable environments. This paper introduces the mesoscale weather chart analysis techniq ue which was tested in the National Meteorological Center (NMC). Mesoscale weath er chart analyzes the favorable environmental conditions of mesoscale convective systems based on observational data and numerical weather forecast outputs. It includes upper air composite chart and surface chart. In the upper air composite ch art, by analyzing wind, temperature, moisture, temperature change and height change, the diagnostic systems and features in all the lower, middle and upper t roposphere isobaric layers are combined into one plot, which can clearly displa y the available environments and synoptic pattern of severe convective weather. In the surface chart, the analysis contents are pressure, wind, temperature, moi sture, convective weather phenomena and all kinds of boundaries (fronts). The te st in NMC shows that mesoscale weather chart analysis is a dependable means for severe convective weather outlook forecasting.
2009,35(1):55-64, DOI: 10.7519/j.issn.1000-0526.2009.1.007
Abstract:
A strong rainstorm is analysis which occurred in Xinghua located the north of Ji angsu province on 25 July 2007. Results show that wind disaster originated from two kinds of rainstorm. One kind was the gust front which occurred at the front of the storm. Strong wind of grade 7-9 was attained when it happened. Another ki nd was the downburst arose in the multi cell storm. The original height of refl ectivity core was higher than -20℃ isotherm. It had the characteristics of conv ergence on the mid level and descending of reflectivity core. The strong wind ab ove grade 10 was attained, when the descending airflow diverged strongly on the ground. A new cell was combined with the former storm above the gust front, thus the storm enhanced. When the downburst happened, the storm weakened, and another new cell was combin ed with the former storm. The downburst happened continuously, and the impact of gust front persisted.
A strong rainstorm is analysis which occurred in Xinghua located the north of Ji angsu province on 25 July 2007. Results show that wind disaster originated from two kinds of rainstorm. One kind was the gust front which occurred at the front of the storm. Strong wind of grade 7-9 was attained when it happened. Another ki nd was the downburst arose in the multi cell storm. The original height of refl ectivity core was higher than -20℃ isotherm. It had the characteristics of conv ergence on the mid level and descending of reflectivity core. The strong wind ab ove grade 10 was attained, when the descending airflow diverged strongly on the ground. A new cell was combined with the former storm above the gust front, thus the storm enhanced. When the downburst happened, the storm weakened, and another new cell was combin ed with the former storm. The downburst happened continuously, and the impact of gust front persisted.
2014,40(4):400-411, DOI: 10.7519/j.issn.1000-0526.2014.04.002
Abstract:
Based on the synoptic environment analysis of about 100 severe convection cases in China since 2000 and the reference of related literatures, from the perspectives of the three essential conditions for the development of severe convection, namely the thermal instability, lift and moisture, five basic synoptic situation configurations of severe convection in China are proposed and expounded. They are cold advection forcing category, warm advection forcing category, baroclinic frontogenesis category, quasi barotropic category and elevated thunderstorm category. The typical characteristics of the upper cold advection forcing category is that the mid upper strong cold advection above 500 hPa strengthens and reaches the boundary warm convergence zone. The warm advection forcing category is characterized by trough with special structure moving over low level strong warm and moist advection. The deep convection produced by the mid lower layer convergence of cold and warm air features the baroclinic frontogenesis category. The quasi barotropic category mostly occurs at the northern and the southern edges or the interior of summer subtropical high and the area with weak baroclinicity, where the dynamic forcing and the surface inhomogeneous local heating play major roles. The features of elevated thunderstorms are the southwest jet in 700-500 hPa lifted by boundary cold wedge and the instable energy is from above 700 hPa. The classification based on the difference of the formation mechanisms can grasp accurately the synoptic characteristics, the situation configurations, the dynamic and thermal properties and the key points in analyzing short term potential forecast, providing more technical support to further enhance the level of weather prediction.
Based on the synoptic environment analysis of about 100 severe convection cases in China since 2000 and the reference of related literatures, from the perspectives of the three essential conditions for the development of severe convection, namely the thermal instability, lift and moisture, five basic synoptic situation configurations of severe convection in China are proposed and expounded. They are cold advection forcing category, warm advection forcing category, baroclinic frontogenesis category, quasi barotropic category and elevated thunderstorm category. The typical characteristics of the upper cold advection forcing category is that the mid upper strong cold advection above 500 hPa strengthens and reaches the boundary warm convergence zone. The warm advection forcing category is characterized by trough with special structure moving over low level strong warm and moist advection. The deep convection produced by the mid lower layer convergence of cold and warm air features the baroclinic frontogenesis category. The quasi barotropic category mostly occurs at the northern and the southern edges or the interior of summer subtropical high and the area with weak baroclinicity, where the dynamic forcing and the surface inhomogeneous local heating play major roles. The features of elevated thunderstorms are the southwest jet in 700-500 hPa lifted by boundary cold wedge and the instable energy is from above 700 hPa. The classification based on the difference of the formation mechanisms can grasp accurately the synoptic characteristics, the situation configurations, the dynamic and thermal properties and the key points in analyzing short term potential forecast, providing more technical support to further enhance the level of weather prediction.
2014,40(2):133-145, DOI: 10.7519/j.issn.1000-0526.2014.02.001
Abstract:
By using the NCEP reanalysis data, the vapor budget of the area covered by the severe torrential rain over the northeast of North China on 21 July, 2012 is calculated according to the vapor budget equation. The results show that meridional water vapor transportation is dominant while the extremely heavy rain hits Beijing Region, where most moist vapor comes from the southern boundary below 500 hPa. The low level regional moisture convergence is consistent with the time and space when the torrential rain breaks out and develops. Above the middle level the vertical vapor transport is more prominent. Then the variation features of the vapor transport corridors and their moisture contributions are got through the HYSPLIT mode. The backward trajectory analyses illustrate two major vapor transport corridors. The moistest vapor derived from Yellow Sea and East China Sea along the low level make the main moisture contribution during the heavy precipitation. Moisture from the South China Sea and the Bay of Bengal strengthens the water vapor in the region when the heavy rain starts and develops. Also the drier vapor corridor along the high level from the northwest of China plays an important role in this case.
By using the NCEP reanalysis data, the vapor budget of the area covered by the severe torrential rain over the northeast of North China on 21 July, 2012 is calculated according to the vapor budget equation. The results show that meridional water vapor transportation is dominant while the extremely heavy rain hits Beijing Region, where most moist vapor comes from the southern boundary below 500 hPa. The low level regional moisture convergence is consistent with the time and space when the torrential rain breaks out and develops. Above the middle level the vertical vapor transport is more prominent. Then the variation features of the vapor transport corridors and their moisture contributions are got through the HYSPLIT mode. The backward trajectory analyses illustrate two major vapor transport corridors. The moistest vapor derived from Yellow Sea and East China Sea along the low level make the main moisture contribution during the heavy precipitation. Moisture from the South China Sea and the Bay of Bengal strengthens the water vapor in the region when the heavy rain starts and develops. Also the drier vapor corridor along the high level from the northwest of China plays an important role in this case.
2012,38(2):164-173, DOI: 10.7519/j.issn.1000-0526.2012.02.004
Abstract:
Many weather forecasters seem to have acquaintance with most of basic concepts or fundamental theories which are connected with severe convection, but some of them are misapplied frequently by some forecasters when they are engaged in severe convective weather analysis or forecasting argumentation. Due to the above problem, some basic concepts and fundamental theories should be explained from the view of forecasting application. The following issues are discussed in this paper. They are the relationship between humidity and water vapor content, the role of clod air during the precipitation process, the fundamental theories connected with thermal and dynamic instability, the sounding analysis related to instability parameters, the relationship between helicity or moist potential vorticity and instability, the relationship among the convergence line, lifting velocity and convective vertical movement, and the essential connection between the synoptic patterns and severe convective phenomena.
Many weather forecasters seem to have acquaintance with most of basic concepts or fundamental theories which are connected with severe convection, but some of them are misapplied frequently by some forecasters when they are engaged in severe convective weather analysis or forecasting argumentation. Due to the above problem, some basic concepts and fundamental theories should be explained from the view of forecasting application. The following issues are discussed in this paper. They are the relationship between humidity and water vapor content, the role of clod air during the precipitation process, the fundamental theories connected with thermal and dynamic instability, the sounding analysis related to instability parameters, the relationship between helicity or moist potential vorticity and instability, the relationship among the convergence line, lifting velocity and convective vertical movement, and the essential connection between the synoptic patterns and severe convective phenomena.
2012,38(1):1-16, DOI: 10.7519/j.issn.1000-0526.2012.01.001
Abstract:
In this paper, the modulation of atmospheric MJO on typhoon generation over the northwestern Pacific and its mechanism are first studied by using the MJO index. The results show that the MJO plays an important modulation role in typhoon generation over the northwestern Pacific: The proportion of typhoon number is 21 between active period and inactive period; During the MJO active period, the proportion of typhoon number is also 2:1 between phases 5-6 and phases 2-3 of MJO. The composite analyses of atmospheric circulation show that there are different circulation patterns over the northwestern Pacific in different phases of the MJO, which will affect the typhoon generation. In phases 5-6 (2-3), the dynamic factor and convective heating patterns over western Pacific are favorable (unfavorable) for typhoon generation. Then， the comparing analyses of the 30-60 day low frequency kinetic energy in lower and higher levels of the troposphere show that the atmospheric intraseasonal oscillation over the northwestern Pacific has a clear impact on the typhoon generation. There is an evident positive (negative) anomaly area of 30-60 day low frequency kinetic energy in the more (less) typhoon years over the northwestern Pacific east of the Philippines, which means that strong (weak) atmospheric intraseasonal oscillation (ISO) over the northwestern Pacific is favorable (unfavorable) for typhoon generation. The analyses of 200 hPa velocity potential show that there is a clear divergence (convergence) pattern over the northwestern Pacific in the more (less) typhoon years, which is favorable (unfavorable) for typhoon generation. The modulation of the intraseasonal oscillation on the typhoon tracks over the northwestern Pacific is studied by observational data analyses. We classified the main classes of typhoon tracks into 5 types as straight west moving typhoons (I), northwest moving typhoons (II), recurving to Korea/west of Japan typhoons (III), landing on Japan typhoons (IV) and recurving to the east of Japan typhoons (V). Then the composite analyses of atmospheric low-frequency wind fields at 850, 500 and 200 hPa, corresponding to the typhoon forming date, for every typhoon track are completed. The analysis results of relationships between the low-frequency (ISO) wind fields and typhoon tracks have indicated that the typhoon tracks will be affected by wind pattern of the ISO. The low frequency positive vorticity belt (the maximum value line of cyclonic vorticity) associated with low-frequency cyclone (LFC) at 850 hPa is so closely related to the typhoon track, that the maximum value line (belt) of low frequency cyclonic vorticity can be an important factor to predicate the typhoon tracks over the northwestern Pacific. And the typhoon tracks will be also affected by the ISO circulation pattern at 200 hPa, particularly the strong low frequency wind associated with low frequency anticyclone (LFAC).
In this paper, the modulation of atmospheric MJO on typhoon generation over the northwestern Pacific and its mechanism are first studied by using the MJO index. The results show that the MJO plays an important modulation role in typhoon generation over the northwestern Pacific: The proportion of typhoon number is 21 between active period and inactive period; During the MJO active period, the proportion of typhoon number is also 2:1 between phases 5-6 and phases 2-3 of MJO. The composite analyses of atmospheric circulation show that there are different circulation patterns over the northwestern Pacific in different phases of the MJO, which will affect the typhoon generation. In phases 5-6 (2-3), the dynamic factor and convective heating patterns over western Pacific are favorable (unfavorable) for typhoon generation. Then， the comparing analyses of the 30-60 day low frequency kinetic energy in lower and higher levels of the troposphere show that the atmospheric intraseasonal oscillation over the northwestern Pacific has a clear impact on the typhoon generation. There is an evident positive (negative) anomaly area of 30-60 day low frequency kinetic energy in the more (less) typhoon years over the northwestern Pacific east of the Philippines, which means that strong (weak) atmospheric intraseasonal oscillation (ISO) over the northwestern Pacific is favorable (unfavorable) for typhoon generation. The analyses of 200 hPa velocity potential show that there is a clear divergence (convergence) pattern over the northwestern Pacific in the more (less) typhoon years, which is favorable (unfavorable) for typhoon generation. The modulation of the intraseasonal oscillation on the typhoon tracks over the northwestern Pacific is studied by observational data analyses. We classified the main classes of typhoon tracks into 5 types as straight west moving typhoons (I), northwest moving typhoons (II), recurving to Korea/west of Japan typhoons (III), landing on Japan typhoons (IV) and recurving to the east of Japan typhoons (V). Then the composite analyses of atmospheric low-frequency wind fields at 850, 500 and 200 hPa, corresponding to the typhoon forming date, for every typhoon track are completed. The analysis results of relationships between the low-frequency (ISO) wind fields and typhoon tracks have indicated that the typhoon tracks will be affected by wind pattern of the ISO. The low frequency positive vorticity belt (the maximum value line of cyclonic vorticity) associated with low-frequency cyclone (LFC) at 850 hPa is so closely related to the typhoon track, that the maximum value line (belt) of low frequency cyclonic vorticity can be an important factor to predicate the typhoon tracks over the northwestern Pacific. And the typhoon tracks will be also affected by the ISO circulation pattern at 200 hPa, particularly the strong low frequency wind associated with low frequency anticyclone (LFAC).
2015,41(2):212-218, DOI: 10.7519/j.issn.1000-0526.2015.02.009
Abstract:
From 1 May to 8 June 2013 CMA Meteorological Observation Centre conducted an experiment of cloud height observations by using cloud radar (35 GHz), whose observation data are the echo power value and temporal resolution is 1 min and a ceilometer whose observation data are the back scattering intens data with 1 min temporal resolution. The result of analyzing the data observed from the 39 d experiment indicates that: (1) the data acquisition ratio of cloud radar is 26% larger than that of ceilometer; (2) the ratio is 51% in fog haze weather; (3) relatively, precipitation has more significant effect on cloud base height measured by laser ceilometer than that by cloud radar; (4) height of cloud base measured by cloud radar is almost consistent with the height by ceilometer because their average deviation is less than 300 m.
From 1 May to 8 June 2013 CMA Meteorological Observation Centre conducted an experiment of cloud height observations by using cloud radar (35 GHz), whose observation data are the echo power value and temporal resolution is 1 min and a ceilometer whose observation data are the back scattering intens data with 1 min temporal resolution. The result of analyzing the data observed from the 39 d experiment indicates that: (1) the data acquisition ratio of cloud radar is 26% larger than that of ceilometer; (2) the ratio is 51% in fog haze weather; (3) relatively, precipitation has more significant effect on cloud base height measured by laser ceilometer than that by cloud radar; (4) height of cloud base measured by cloud radar is almost consistent with the height by ceilometer because their average deviation is less than 300 m.
2011,37(10):1262-1269, DOI: 10.7519/j.issn.1000-0526.2011.10.009
Abstract:
Based on the daily precipitation data at 110 observational stations during 1961-2008 in South China， the climatic characteristics and variation of torrential rain days， rainstorm intensity and contribution which is in annual， the first and second flood seasons in South China were studied by using statistical and diagnostic methods， such as linear regression analysis， Mann Kendall test， wavelet analysis and the computation of trend coefficients. The results have shown that the annual mean torrential rain days have a decreasing trend from coastal regions to inland in South China in recent 48 years， the highest center is in Dongxing of Guangxi （14.9 d）， and the lowest center is in Longlin of Guangxi （3.2 d）. About 72% of the total torrential rain days occurred in the flood seasons with about 45% in the first season and 27% in the second season. The mean torrential rain days have increased faintly in annual， the first and second flood seasons in South China， but it is not obvious. There are the characteristics of interannual and interdecadal changes. The mean rainstorm intensity has increased faintly in annual and in the first flood season in South China. However, since 2005 it has become obviously. The mean rainstorm intensity has declined in the second flood season， but it is not obvious. The annual mean rainstorm contribution to the total rainfall has increased obviously， but the mean contribution is not obvious in the first and second flood seasons. The wavelet analysis has shown that the changes of torrential rain days， intensity and contribution which is in annual， the first and second flood seasons in South China have two significant periods of 2-3 a and 3-4 a.
Based on the daily precipitation data at 110 observational stations during 1961-2008 in South China， the climatic characteristics and variation of torrential rain days， rainstorm intensity and contribution which is in annual， the first and second flood seasons in South China were studied by using statistical and diagnostic methods， such as linear regression analysis， Mann Kendall test， wavelet analysis and the computation of trend coefficients. The results have shown that the annual mean torrential rain days have a decreasing trend from coastal regions to inland in South China in recent 48 years， the highest center is in Dongxing of Guangxi （14.9 d）， and the lowest center is in Longlin of Guangxi （3.2 d）. About 72% of the total torrential rain days occurred in the flood seasons with about 45% in the first season and 27% in the second season. The mean torrential rain days have increased faintly in annual， the first and second flood seasons in South China， but it is not obvious. There are the characteristics of interannual and interdecadal changes. The mean rainstorm intensity has increased faintly in annual and in the first flood season in South China. However, since 2005 it has become obviously. The mean rainstorm intensity has declined in the second flood season， but it is not obvious. The annual mean rainstorm contribution to the total rainfall has increased obviously， but the mean contribution is not obvious in the first and second flood seasons. The wavelet analysis has shown that the changes of torrential rain days， intensity and contribution which is in annual， the first and second flood seasons in South China have two significant periods of 2-3 a and 3-4 a.
2014,40(7):816-826, DOI: 10.7519/j.issn.1000-0526.2014.07.005
Abstract:
In term of precipitation data of 2400 stations from 1981 to 2010, annual, seasonal and monthly distribution and evolution characteristics of rainstorm were analyzed. The results show that the processes of rainstorm have been increased evidently since 21 century especially in the south of China, but the duration is relatively short. Rainstorm days have been increased, but the amount of precipitation is not as much as in 1990s. Variation trend of the annual (monthly) precipitation amount is in accordance with that of rainstorm days, but rainfall is averagely more while the rainstorm days are less during spring rainfall phase over the south of Yangtze River. Distribution of the maximum annual rainstorm days is very similar with that of the annual mean rainstorm days, revealing the feature of more in south and east but less in north and west. Maximum annual rainstorm days are more than double of annual average rainstorm days with multi centers due to the effect of topography. The months of maximum monthly rainstorm days over different regions of the same province are incompletely same as the result of the impact of different weather systems. Generally, rainstorm days have been increased since 2000, rainstorm begins earlier, ends latter and lasts longer than before. Nowadays, as the extreme rainfall events and secondary disasters happen frequently, it is conducive for the forecast of quantitative precipitation forecast (QPF) to learn the spatio temporal distribution and evolution features of rainstorm.
In term of precipitation data of 2400 stations from 1981 to 2010, annual, seasonal and monthly distribution and evolution characteristics of rainstorm were analyzed. The results show that the processes of rainstorm have been increased evidently since 21 century especially in the south of China, but the duration is relatively short. Rainstorm days have been increased, but the amount of precipitation is not as much as in 1990s. Variation trend of the annual (monthly) precipitation amount is in accordance with that of rainstorm days, but rainfall is averagely more while the rainstorm days are less during spring rainfall phase over the south of Yangtze River. Distribution of the maximum annual rainstorm days is very similar with that of the annual mean rainstorm days, revealing the feature of more in south and east but less in north and west. Maximum annual rainstorm days are more than double of annual average rainstorm days with multi centers due to the effect of topography. The months of maximum monthly rainstorm days over different regions of the same province are incompletely same as the result of the impact of different weather systems. Generally, rainstorm days have been increased since 2000, rainstorm begins earlier, ends latter and lasts longer than before. Nowadays, as the extreme rainfall events and secondary disasters happen frequently, it is conducive for the forecast of quantitative precipitation forecast (QPF) to learn the spatio temporal distribution and evolution features of rainstorm.
2014,40(4):389-399, DOI: 10.7519/j.issn.1000-0526.2014.04.001
Abstract:
Thunderstorm potential forecasting based on three ingredients has been widely accepted. This article aims to discuss some basical questions in operational forecast applications, and clarify some easily confused concepts. The content includes atmospheric instablility and convection, thunderstorms trigger mechanism and lifting and its relationship with snoptical weather system, how to deal with the three elements of the thunderstorm “enough”, the combination of pattern recognition and ingredients based forecasting methodology. Atmospheric instablility is one of the three ingredients of convection initiation, and it is also very important to thunderstorm short time forecasting and analysis. This paper discusses various mesoscale instability related to the thunderstorm, and inicates how to estimate the spatial and temporal evolution of CAPE. In addition, the definition and criterion for potential instability and symmetric instability are discussed profoundly.
Thunderstorm potential forecasting based on three ingredients has been widely accepted. This article aims to discuss some basical questions in operational forecast applications, and clarify some easily confused concepts. The content includes atmospheric instablility and convection, thunderstorms trigger mechanism and lifting and its relationship with snoptical weather system, how to deal with the three elements of the thunderstorm “enough”, the combination of pattern recognition and ingredients based forecasting methodology. Atmospheric instablility is one of the three ingredients of convection initiation, and it is also very important to thunderstorm short time forecasting and analysis. This paper discusses various mesoscale instability related to the thunderstorm, and inicates how to estimate the spatial and temporal evolution of CAPE. In addition, the definition and criterion for potential instability and symmetric instability are discussed profoundly.
2011,37(5):599-606, DOI: 10.7519/j.issn.1000-0526.2011.5.012
Abstract:
Using the diurnal snow data of 120 meteorological stations in Yunnan Province during 1961-2008, the temporal and spatial distribution characteristics and the trend of climatic change of the annual and monthly snow fall are analyzed. It is pointed out that the total trend of snow frequency and covering stations has been decreasing in Yunnan in the recent 50 years. And the annual snow frequency has declined at a mean rate of 4.5 times per year. The temporal trends of monthly snow frequency and covering stations are all negative. Moreover the reduction of snow frequency in December is the largest in magnitude, therefore, it is the most remarkable. And the reduction of snow stations in April is the largest. As far as the spatial change of the secular trend variation of annual snow frequency is concerned, the reduction of annual snow frequency is larger in Northwest Yunnan than in its northeast and east, where the reduction rate is 0.44 times per year. And the temporal changes of annual snowfall and depth of snow cover are studied, the results show that the secular trends of annual snowfall and the maximum depth of snow cover are all positive. This means that in the nearly 50 years the heavy snow frequency has increased over Yunnan Province.
Using the diurnal snow data of 120 meteorological stations in Yunnan Province during 1961-2008, the temporal and spatial distribution characteristics and the trend of climatic change of the annual and monthly snow fall are analyzed. It is pointed out that the total trend of snow frequency and covering stations has been decreasing in Yunnan in the recent 50 years. And the annual snow frequency has declined at a mean rate of 4.5 times per year. The temporal trends of monthly snow frequency and covering stations are all negative. Moreover the reduction of snow frequency in December is the largest in magnitude, therefore, it is the most remarkable. And the reduction of snow stations in April is the largest. As far as the spatial change of the secular trend variation of annual snow frequency is concerned, the reduction of annual snow frequency is larger in Northwest Yunnan than in its northeast and east, where the reduction rate is 0.44 times per year. And the temporal changes of annual snowfall and depth of snow cover are studied, the results show that the secular trends of annual snowfall and the maximum depth of snow cover are all positive. This means that in the nearly 50 years the heavy snow frequency has increased over Yunnan Province.
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ISSN:1000-0526 CN:11-2282/P