ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 51,2025 Issue 12
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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(12):1581-1595, DOI: 10.7519/j.issn.1000-0526.2025.090801
Abstract:
In order to explore the detection ability of X-band phased-array radar for extreme precipitation, based on the basic products of X-band phased-array radar and three-dimensional wind field reversal from June to August in 2023 and 2024, the dual-polarization parameter characteristics of 9 extreme precipitation events in two years’ summer and the storm structure of 3 typical precipitation processes are analyzed by statistical and diagnostic analysis methods. The results show that the mean and median values of horizontal polarization reflectivity factor (ZH), differential reflectivity factor (ZDR) and specific differential phase (KDP) below 4 km gradually increase with the increase of minutely precipitation intensity. KDP increases most obviously. The KDP of super heavy precipitation >2.5 mm·min-1 increases by 30%-246% compared with the lowest level of 1-1.5 mm·min-1 at each altitude, and increases by 15%-167% compared with the lower level of 2-2.5 mm·min-1. ZH and KDP decrease with increasing altitude, and the maximum values are in the height of 0-1 km. The dual-polarization parameters of the lower layer gradually increase 3-10 min before the extreme minutely precipitation, and decrease 2-5 min after the extreme value, with the maximum fluctuation range of KDP. Under the 2 km height, the increase of KDP before the extreme value is 133%-205%, and the decrease range after the extreme value is 49%-55%. The intensity of the minutely precipitation depends mainly on the KDP (particle concentration). By analyzing the characteristics of extreme precipitation storm, we can see that the storm belongs to backward propagation type, with a new cell born every 4-6 min on the west side and its whole life span ≥65 min. There is a convergence zone of 4-5 km thick in the storm. The ZDR maximum center of the storm is below 3 km, and larger raindrops are concentrated in the lower layer. The possible reason for the increase of KDP laging behind the increase of ZDR is that during the descending process, the raindrops first grow in size and then break up into smaller high-concentration raindrops.
In order to explore the detection ability of X-band phased-array radar for extreme precipitation, based on the basic products of X-band phased-array radar and three-dimensional wind field reversal from June to August in 2023 and 2024, the dual-polarization parameter characteristics of 9 extreme precipitation events in two years’ summer and the storm structure of 3 typical precipitation processes are analyzed by statistical and diagnostic analysis methods. The results show that the mean and median values of horizontal polarization reflectivity factor (ZH), differential reflectivity factor (ZDR) and specific differential phase (KDP) below 4 km gradually increase with the increase of minutely precipitation intensity. KDP increases most obviously. The KDP of super heavy precipitation >2.5 mm·min-1 increases by 30%-246% compared with the lowest level of 1-1.5 mm·min-1 at each altitude, and increases by 15%-167% compared with the lower level of 2-2.5 mm·min-1. ZH and KDP decrease with increasing altitude, and the maximum values are in the height of 0-1 km. The dual-polarization parameters of the lower layer gradually increase 3-10 min before the extreme minutely precipitation, and decrease 2-5 min after the extreme value, with the maximum fluctuation range of KDP. Under the 2 km height, the increase of KDP before the extreme value is 133%-205%, and the decrease range after the extreme value is 49%-55%. The intensity of the minutely precipitation depends mainly on the KDP (particle concentration). By analyzing the characteristics of extreme precipitation storm, we can see that the storm belongs to backward propagation type, with a new cell born every 4-6 min on the west side and its whole life span ≥65 min. There is a convergence zone of 4-5 km thick in the storm. The ZDR maximum center of the storm is below 3 km, and larger raindrops are concentrated in the lower layer. The possible reason for the increase of KDP laging behind the increase of ZDR is that during the descending process, the raindrops first grow in size and then break up into smaller high-concentration raindrops.
2025,51(12):1596-1607, DOI: 10.7519/j.issn.1000-0526.2024.122601
Abstract:
From 29 to 30 June 2023, a localized abrupt severe torrential rain occurred in the western region of Hunan Province, but forecasters and numerical models both failed to forecast the rainfall intensity. In this study, the mesoscale characteristics and possible causes of forecast biases are analyzed based on the multiple observations data, ERA5 reanalysis data and numerical forecast products. The results show that the northwest air flow behind the upper-level trough drove the cold air to the south and merged with the southwest warm-humid air flows which were strengthened at night, which led to the occurrence of this process. The severe torrential rain was generated by a backward propagation of quasi-stationary mesoscale convective system (MCS), which was composed of multiple strongly developing γ-MCSs, manifested as an organized linear echo band. Under the favorable environmental background, the long-time maintenance of the boundary layer convergence line, the wind velocity fluctuation of the low-level jet and the vertical structure of low-level convergence and high-level divergence contributed to the triggering and organization of the convective cells. The merging, strengthening backward propagation of MCS and the train effect of convective cells were important causes for the severe torrential rain. Significant errors were made in the short-time subjective forecasts because of the forecast biases of the low-level dynamic and thermodynamic fields of the numerical models, the deficiency of forecasters’ ability to correct the model forecast, and the complex topography of western Hunan Province. Therefore, it is very crucial to use the automatic weather station data, satellite data and radar data with high spatio-temporal resolution to analyze the changes of the mesoscale environmental conditions, strengthen the short-time nowcasting and issue early warning in time.
From 29 to 30 June 2023, a localized abrupt severe torrential rain occurred in the western region of Hunan Province, but forecasters and numerical models both failed to forecast the rainfall intensity. In this study, the mesoscale characteristics and possible causes of forecast biases are analyzed based on the multiple observations data, ERA5 reanalysis data and numerical forecast products. The results show that the northwest air flow behind the upper-level trough drove the cold air to the south and merged with the southwest warm-humid air flows which were strengthened at night, which led to the occurrence of this process. The severe torrential rain was generated by a backward propagation of quasi-stationary mesoscale convective system (MCS), which was composed of multiple strongly developing γ-MCSs, manifested as an organized linear echo band. Under the favorable environmental background, the long-time maintenance of the boundary layer convergence line, the wind velocity fluctuation of the low-level jet and the vertical structure of low-level convergence and high-level divergence contributed to the triggering and organization of the convective cells. The merging, strengthening backward propagation of MCS and the train effect of convective cells were important causes for the severe torrential rain. Significant errors were made in the short-time subjective forecasts because of the forecast biases of the low-level dynamic and thermodynamic fields of the numerical models, the deficiency of forecasters’ ability to correct the model forecast, and the complex topography of western Hunan Province. Therefore, it is very crucial to use the automatic weather station data, satellite data and radar data with high spatio-temporal resolution to analyze the changes of the mesoscale environmental conditions, strengthen the short-time nowcasting and issue early warning in time.
2025,51(12):1608-1620, DOI: 10.7519/j.issn.1000-0526.2025.060602
Abstract:
Utilizing the best track data of tropical cyclones from China Meteorological Administration (CMA) in 1949-2024, observed data of typhoon track and intensity from National Meteorological Centre (NMC) in 2024, and ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF), this paper analyzes the main characteristics of typhoon activities over the Northwest Pacific and South China Sea in 2024. The results indicate that the number of generated typhoons and average maximum intensity in typhoon lifespan approximated climatological mean, with their average birth locations by north and by west. The landfall typhoon count surpassed the climatological mean with enhanced intensity and concentrated impact areas. The autumn typhoon activities significantly exceeded climatological mean. Notable inland movement of the typhoons caused extensive heavy precipitation processes. The NMC demonstrated superior track forecasting capability compared to the Japan Meteorological Agency (JMA) and the U.S. Joint Typhoon Warning Center (JTWC), while the typhoon intensity prediction errors by NMC exceeded that of JMA but was lower than that of JTWC. Key challenging issues in the operational forecasting include that, firstly, significant track forecast errors arose from numerical models’ limited capability in catching the complex structural evolution of typhoons after their landfall and their interactions with steering flows, which makes the correction to such processes highly challenging. Then, forecasting the persistence of typhoon remnant vortices over land and their associated precipitation impacts is the second challenging issue, and the third difficulty is predicting the rapid intensification (RI) of Typhoon Yagi and the prolonged maintenance of super typhoon.
Utilizing the best track data of tropical cyclones from China Meteorological Administration (CMA) in 1949-2024, observed data of typhoon track and intensity from National Meteorological Centre (NMC) in 2024, and ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF), this paper analyzes the main characteristics of typhoon activities over the Northwest Pacific and South China Sea in 2024. The results indicate that the number of generated typhoons and average maximum intensity in typhoon lifespan approximated climatological mean, with their average birth locations by north and by west. The landfall typhoon count surpassed the climatological mean with enhanced intensity and concentrated impact areas. The autumn typhoon activities significantly exceeded climatological mean. Notable inland movement of the typhoons caused extensive heavy precipitation processes. The NMC demonstrated superior track forecasting capability compared to the Japan Meteorological Agency (JMA) and the U.S. Joint Typhoon Warning Center (JTWC), while the typhoon intensity prediction errors by NMC exceeded that of JMA but was lower than that of JTWC. Key challenging issues in the operational forecasting include that, firstly, significant track forecast errors arose from numerical models’ limited capability in catching the complex structural evolution of typhoons after their landfall and their interactions with steering flows, which makes the correction to such processes highly challenging. Then, forecasting the persistence of typhoon remnant vortices over land and their associated precipitation impacts is the second challenging issue, and the third difficulty is predicting the rapid intensification (RI) of Typhoon Yagi and the prolonged maintenance of super typhoon.
2025,51(12):1621-1634, DOI: 10.7519/j.issn.1000-0526.2025.091701
Abstract:
In 2023, tropical cyclone activity over the Northwest Pacific had the characteristics of lower frequency but higher intensity. Six damaging tropical cyclones or typhoons impacted China, and typhoon disasters exhibited a concentrated manifestation during the autumn. Driven by the transition phase of El Nino superimposed on anomalously warm sea surface temperature and associated atmospheric circulation anomalies in the North Pacific, typhoons brought record-breaking hourly precipitation extremums unseen in 1984-2022 in China, while their wind speed impacts were generally comparable to historical averages. Regarding disaster losses, these typhoons collectively resulted in 12 fatalities/missing persons, 7000 collapsed houses, an affected crop area of 34.76×104 hm2, and direct economic losses amounting to 47.49 billion yuan. All disaster loss metrics were significantly lower than the averages of 1984-2022. A pronounced discrepancy emerged when comparing standardized disaster impact indices. The percentile ranking of the Comprehensive Typhoon Disaster Impact Index was, on average, 26.1 percentage points lower than that of the Integrated Precipitation and Wind Impact Index. This significant contrast primarily stems from the effectiveness of the disaster prevention and mitigation system. Meteorological departments provided crucial support for risk preparedness through accurate forecasts for typhoon tracks and torrential rain bands. Furthermore, efficient coordination among emergency management agencies at all levels, which was achieved by comprehensive measures such as pre-disaster risk management and emergency interagency response, played a pivotal role in significantly reducing disaster losses.
In 2023, tropical cyclone activity over the Northwest Pacific had the characteristics of lower frequency but higher intensity. Six damaging tropical cyclones or typhoons impacted China, and typhoon disasters exhibited a concentrated manifestation during the autumn. Driven by the transition phase of El Nino superimposed on anomalously warm sea surface temperature and associated atmospheric circulation anomalies in the North Pacific, typhoons brought record-breaking hourly precipitation extremums unseen in 1984-2022 in China, while their wind speed impacts were generally comparable to historical averages. Regarding disaster losses, these typhoons collectively resulted in 12 fatalities/missing persons, 7000 collapsed houses, an affected crop area of 34.76×104 hm2, and direct economic losses amounting to 47.49 billion yuan. All disaster loss metrics were significantly lower than the averages of 1984-2022. A pronounced discrepancy emerged when comparing standardized disaster impact indices. The percentile ranking of the Comprehensive Typhoon Disaster Impact Index was, on average, 26.1 percentage points lower than that of the Integrated Precipitation and Wind Impact Index. This significant contrast primarily stems from the effectiveness of the disaster prevention and mitigation system. Meteorological departments provided crucial support for risk preparedness through accurate forecasts for typhoon tracks and torrential rain bands. Furthermore, efficient coordination among emergency management agencies at all levels, which was achieved by comprehensive measures such as pre-disaster risk management and emergency interagency response, played a pivotal role in significantly reducing disaster losses.
2025,51(12):1635-1644, DOI: 10.7519/j.issn.1000-0526.2025.073001
Abstract:
Based on the 10 min observation data from the traffic meteorological stations along the Tianjin expressway during 2018-2023, a long short-term memory network model is used to forecast the pavement temperature in the next 3 h, and the forecasting effect and spatial transfer applicability of the model in the case of extreme pavement temperatures are evaluated and analyzed. The results show that the model forecasting effect is the best when the observation data of the time step 3 h are used as the input. The model can forecast the pavement temperature accurately, and the forecasting ability decreases with the extension of the forecast lead time, with the mean absolute error of 0.38-2.21℃, the root mean square error of 0.63-3.31℃, and the accuracy rate of 76.15%-99.48%. The model can accurately forecast the occurrence time and extreme values of extreme low temperature events on pavements, with the forecasting accuracy being about 90% for the 1 h forecast. For extreme high pavement temperature, the 1 h forecast of the model can also simulate the variation trend and the time for extreme high pavement temperature to occur. The model has a certain spatial transfer ability, and the average accuracy of the model forecast is more than 70% after the transfer, with an mean absolute deviation less than 3℃. Within a certain range, compared with the transfer distance, the forecasting ability of the model at its original station has a greater impact on the forecasting performance of the model after transfer.
Based on the 10 min observation data from the traffic meteorological stations along the Tianjin expressway during 2018-2023, a long short-term memory network model is used to forecast the pavement temperature in the next 3 h, and the forecasting effect and spatial transfer applicability of the model in the case of extreme pavement temperatures are evaluated and analyzed. The results show that the model forecasting effect is the best when the observation data of the time step 3 h are used as the input. The model can forecast the pavement temperature accurately, and the forecasting ability decreases with the extension of the forecast lead time, with the mean absolute error of 0.38-2.21℃, the root mean square error of 0.63-3.31℃, and the accuracy rate of 76.15%-99.48%. The model can accurately forecast the occurrence time and extreme values of extreme low temperature events on pavements, with the forecasting accuracy being about 90% for the 1 h forecast. For extreme high pavement temperature, the 1 h forecast of the model can also simulate the variation trend and the time for extreme high pavement temperature to occur. The model has a certain spatial transfer ability, and the average accuracy of the model forecast is more than 70% after the transfer, with an mean absolute deviation less than 3℃. Within a certain range, compared with the transfer distance, the forecasting ability of the model at its original station has a greater impact on the forecasting performance of the model after transfer.
2025,51(12):1645-1655, DOI: 10.7519/j.issn.1000-0526.2025.071101
Abstract:
This paper constructs a deep learning model based on the sequential fusion encoder (SFE) for forecasting winter precipitation phase. The model integrates the advantages of convolutional neural network (CNN), convolutional gated recurrent unit (ConvGRU), and Transformer. It can conduct automatic learning and extraction of complex features from meteorological data, handle non-linear relationships, and process large-scale datasets. We utilize hourly precipitation observation data from Wuhan Station in 2010-2024 and ERA5 reanalysis data, select 60-channel grid data (including temperature and geopotential height) from 9 atmospheric layers (1000-500 hPa) as predictors. To address sample imbalance, minute-level data augmentation is employed, involving resampling at intervals of 30 min for rain, 1 min for sleet, and 5 min for snow. Finally, a sample size of 19 932 is obtained. Test results show that this model performs excellently in forecasting solid precipitation (snow and sleet), with F1-scores of 0.92-0.93 in the training set and 0.67-0.68 in the validation set. However, its ability to identify rapid transitions between precipitation phases needs to be improved. Verified by two complex weather processes in February 2024, the model is found to be able to serve as a supplement to numerical prediction and provide an efficient solution for intelligent forecasting of winter precipitation phase, aiding in enhancing the forecasting capabilities of meteorological stations.
This paper constructs a deep learning model based on the sequential fusion encoder (SFE) for forecasting winter precipitation phase. The model integrates the advantages of convolutional neural network (CNN), convolutional gated recurrent unit (ConvGRU), and Transformer. It can conduct automatic learning and extraction of complex features from meteorological data, handle non-linear relationships, and process large-scale datasets. We utilize hourly precipitation observation data from Wuhan Station in 2010-2024 and ERA5 reanalysis data, select 60-channel grid data (including temperature and geopotential height) from 9 atmospheric layers (1000-500 hPa) as predictors. To address sample imbalance, minute-level data augmentation is employed, involving resampling at intervals of 30 min for rain, 1 min for sleet, and 5 min for snow. Finally, a sample size of 19 932 is obtained. Test results show that this model performs excellently in forecasting solid precipitation (snow and sleet), with F1-scores of 0.92-0.93 in the training set and 0.67-0.68 in the validation set. However, its ability to identify rapid transitions between precipitation phases needs to be improved. Verified by two complex weather processes in February 2024, the model is found to be able to serve as a supplement to numerical prediction and provide an efficient solution for intelligent forecasting of winter precipitation phase, aiding in enhancing the forecasting capabilities of meteorological stations.
2025,51(12):1656-1668, DOI: 10.7519/j.issn.1000-0526.2025.091901
Abstract:
Summer is a critical period for fishery production. Fishpond water has high temperature and low saturated dissolved oxygen, while aquatic organisms have vigorous metabolism and high oxygen consumption, so often leading to oxygen deficiency and economic losses. Dissolved oxygen monitoring equipment is limited by pond water quality, making it difficult to ensure monitoring accuracy. Research on meteorological prediction models for dissolved oxygen in summer aquaculture water can offer references for regulating dissolved oxygen, warning fishpond suffocation risks and integrating intelligent oxygenation systems, and can also offer solutions for improving fishpond water quality monitoring accuracy. Based on in-situ monitored dissolved oxygen and water temperature data in different layers of freshwater in fishponds and observed meteorological data from meteorological stations in Jianghan Plain, the spatio-temporal variation of layered dissolved oxygen in summer is analyzed. A real-time prediction model for dissolved oxygen based onmeteorological factors is established using the RF-SVR method and is compared with other models. The results show that the variation characteristics of dissolved oxygen in different layers are significant in sunny and hot weather in summer, that is, the dissolved oxygen starts to rise at 07:00-08:00 BT, decreases vertically with water depth, peaks at 17:00-20:00 BT, and then begins to decrease, with values in different layers getting close to each other gradually, and its lowest level appears at 03:00-08:00 BT. Under severe cooling and low-light conditions, pond dissolved oxygen rapidly drops to below 2 mg·L-1 and maintains a low-oxygen environment. Partial dependence analysis indicates that summer solar radiation exposure, sea-level pressure and maximum temperature are the main limiting factors for dissolved oxygen changes in aquaculture ponds and have a significant lag effect. The values of MAE, NSE, R2 and RMSE of meteorological prediction model for dissolved oxygen based on RF-SVR are 0.50 mg·L-1, 0.63, 0.77 and 0.66 mg·L-1 respectively, showing better simulation accuracy and smaller errors than those of other seven models and being more suitable for summer dissolved oxygen prediction.
Summer is a critical period for fishery production. Fishpond water has high temperature and low saturated dissolved oxygen, while aquatic organisms have vigorous metabolism and high oxygen consumption, so often leading to oxygen deficiency and economic losses. Dissolved oxygen monitoring equipment is limited by pond water quality, making it difficult to ensure monitoring accuracy. Research on meteorological prediction models for dissolved oxygen in summer aquaculture water can offer references for regulating dissolved oxygen, warning fishpond suffocation risks and integrating intelligent oxygenation systems, and can also offer solutions for improving fishpond water quality monitoring accuracy. Based on in-situ monitored dissolved oxygen and water temperature data in different layers of freshwater in fishponds and observed meteorological data from meteorological stations in Jianghan Plain, the spatio-temporal variation of layered dissolved oxygen in summer is analyzed. A real-time prediction model for dissolved oxygen based onmeteorological factors is established using the RF-SVR method and is compared with other models. The results show that the variation characteristics of dissolved oxygen in different layers are significant in sunny and hot weather in summer, that is, the dissolved oxygen starts to rise at 07:00-08:00 BT, decreases vertically with water depth, peaks at 17:00-20:00 BT, and then begins to decrease, with values in different layers getting close to each other gradually, and its lowest level appears at 03:00-08:00 BT. Under severe cooling and low-light conditions, pond dissolved oxygen rapidly drops to below 2 mg·L-1 and maintains a low-oxygen environment. Partial dependence analysis indicates that summer solar radiation exposure, sea-level pressure and maximum temperature are the main limiting factors for dissolved oxygen changes in aquaculture ponds and have a significant lag effect. The values of MAE, NSE, R2 and RMSE of meteorological prediction model for dissolved oxygen based on RF-SVR are 0.50 mg·L-1, 0.63, 0.77 and 0.66 mg·L-1 respectively, showing better simulation accuracy and smaller errors than those of other seven models and being more suitable for summer dissolved oxygen prediction.
2025,51(12):1669-1682, DOI: 10.7519/j.issn.1000-0526.2025.090101
Abstract:
Errors of typhoon operational position and intensity estimation, as well as errors of typhoon track and intensity forecast over the Northwest Pacific and the South China Sea in 2023 are evaluated. The results show that the mean error of typhoon position estimation by official typhoon forecasting agencies in 2023 was 17.1 km, and the mean error of typhoon intensity estimation was 2.8 m·s-1. Compared to the errors in 2022, the accuracy of typhoon position estimation got improved in 2023, whereas the accuracy of typhoon intensity estimation decreased. The mean errors of track forecasts with 24， 48 and 72 h lead time by subjective and objective forecast methods in 2023 were reduced than in 2022. In 2023, the mean errors of 24 h track forecast by the official typhoon forecasting agencies reached a historic low. Among objective forecasts, mean errors of track forecasts by ECMWF-IFS, NCEP-GFS, CMA-TRAMS were relatively small. Mean absolute errors of typhoon intensity forecasts by NCEP-GFS, CMA-TYM and ANNGA were generally small, and their intensity forecast skill scores were relatively high.
Errors of typhoon operational position and intensity estimation, as well as errors of typhoon track and intensity forecast over the Northwest Pacific and the South China Sea in 2023 are evaluated. The results show that the mean error of typhoon position estimation by official typhoon forecasting agencies in 2023 was 17.1 km, and the mean error of typhoon intensity estimation was 2.8 m·s-1. Compared to the errors in 2022, the accuracy of typhoon position estimation got improved in 2023, whereas the accuracy of typhoon intensity estimation decreased. The mean errors of track forecasts with 24， 48 and 72 h lead time by subjective and objective forecast methods in 2023 were reduced than in 2022. In 2023, the mean errors of 24 h track forecast by the official typhoon forecasting agencies reached a historic low. Among objective forecasts, mean errors of track forecasts by ECMWF-IFS, NCEP-GFS, CMA-TRAMS were relatively small. Mean absolute errors of typhoon intensity forecasts by NCEP-GFS, CMA-TYM and ANNGA were generally small, and their intensity forecast skill scores were relatively high.
2025,51(12):1683-1692, DOI: 10.7519/j.issn.1000 0526.2025.111701
Abstract:
The general atmospheric circulation in September 2025 was characterized by the following key features: the Northern Hemisphere polar vortex exhibited a single core structure, and biased toward the Eastern Hemisphere. The western Pacific subtropical high (WPSH) was stronger than usual, with its ridge extending farther westward and northward. Under its persistent control, prolonged high temperature conditions occurred in southern China. The warm and humid airflow on the edge of the WPSH converged with cold air moving southward, leading to significantly increased autumn rain in West China. Most of northern China was influenced by relatively flat westerly flow, with limited incursions of cold air. The temperature in North China and Northeast China was relatively high and the precipitation was relatively low. A total of six tropical cyclones or typhoons formed in the month, three of which made landfall in China, and the both figures exceeded the climatological normal by 1 and 1.3, respectively. On 18 September, tyhpoons Mitag, Ragasa and Neoguri successively formed and coexisted. Mitag， Ragasa and Bualoi tracked northwestward, affecting South China, etc. Super Typhoon Ragasa made landfall three times along the southern coast, accompanied by strong winds and prolonged influence. Persistent moisture transport by the WPSH, combined with the effects of tropical cyclones, resulted in significant precipitation across South China. The monthly mean temperature across China was 18.1℃, 1.2℃ above normal, ranking as the fourth highest since 1961. The national average monthly precipitation reached 87.6 mm, 34% above the normal, making it the third in September since 1961. In addition, eight major heavy precipitation processes and four severe convective weather processes were recorded during this month.
The general atmospheric circulation in September 2025 was characterized by the following key features: the Northern Hemisphere polar vortex exhibited a single core structure, and biased toward the Eastern Hemisphere. The western Pacific subtropical high (WPSH) was stronger than usual, with its ridge extending farther westward and northward. Under its persistent control, prolonged high temperature conditions occurred in southern China. The warm and humid airflow on the edge of the WPSH converged with cold air moving southward, leading to significantly increased autumn rain in West China. Most of northern China was influenced by relatively flat westerly flow, with limited incursions of cold air. The temperature in North China and Northeast China was relatively high and the precipitation was relatively low. A total of six tropical cyclones or typhoons formed in the month, three of which made landfall in China, and the both figures exceeded the climatological normal by 1 and 1.3, respectively. On 18 September, tyhpoons Mitag, Ragasa and Neoguri successively formed and coexisted. Mitag， Ragasa and Bualoi tracked northwestward, affecting South China, etc. Super Typhoon Ragasa made landfall three times along the southern coast, accompanied by strong winds and prolonged influence. Persistent moisture transport by the WPSH, combined with the effects of tropical cyclones, resulted in significant precipitation across South China. The monthly mean temperature across China was 18.1℃, 1.2℃ above normal, ranking as the fourth highest since 1961. The national average monthly precipitation reached 87.6 mm, 34% above the normal, making it the third in September since 1961. In addition, eight major heavy precipitation processes and four severe convective weather processes were recorded during this month.
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Available online: January 04, 2026 , DOI: 10.7519/j.issn.1000-0526.2025.122501
Abstract:
Similarity forecasting is a statistical forecasting method widely used in operational services. To overcome the limitations of single-layer similarity, which lacks three-dimensional spatial information and suffers from unstable performance due to the frequent interference of weather system shapes and values, this paper explores the feasibility of deep learning models in weather situation recognition and forecasting. Using ERA5 reanalysis data, we construct a deep learning model based on CNN and Transformer modules, incorporating a self-attention mechanism. The model is trained and optimized, and the test results indicate that it can accurately extract the three-dimensional spatial information of weather situations. We then combine the Pearson correlation, which emphasizes shape, the Euclidean distance, which emphasizes value, and the Chebyshev criterion, which comprehensively considers both shape and value, to design a new weather situation similarity forecasting method, SynopticSimNet (SSN). Finally, we conduct a detailed evaluation of its practical performance. The results show that: (1) the SSN method achieves the highest average SSIM and the lowest MSE, with a significant improvement in SSIM and reduction in MSE compared to traditional methods; (2) Analysis of cases from two different seasons shows that the best historical similar cases identified by SSN are not only numerically closer to the original field but also exhibit the most consistent spatial distribution, demonstrating the method"s promising potential for operational application.
Similarity forecasting is a statistical forecasting method widely used in operational services. To overcome the limitations of single-layer similarity, which lacks three-dimensional spatial information and suffers from unstable performance due to the frequent interference of weather system shapes and values, this paper explores the feasibility of deep learning models in weather situation recognition and forecasting. Using ERA5 reanalysis data, we construct a deep learning model based on CNN and Transformer modules, incorporating a self-attention mechanism. The model is trained and optimized, and the test results indicate that it can accurately extract the three-dimensional spatial information of weather situations. We then combine the Pearson correlation, which emphasizes shape, the Euclidean distance, which emphasizes value, and the Chebyshev criterion, which comprehensively considers both shape and value, to design a new weather situation similarity forecasting method, SynopticSimNet (SSN). Finally, we conduct a detailed evaluation of its practical performance. The results show that: (1) the SSN method achieves the highest average SSIM and the lowest MSE, with a significant improvement in SSIM and reduction in MSE compared to traditional methods; (2) Analysis of cases from two different seasons shows that the best historical similar cases identified by SSN are not only numerically closer to the original field but also exhibit the most consistent spatial distribution, demonstrating the method"s promising potential for operational application.
Available online: January 04, 2026 , DOI: 10.7519/j.issn.1000-0526.2025.092801
Abstract:
In order to systematically investigate the evolution characteristics and mechanisms of squall lines descending mountains in Northern Shanxi, this study utilized the following datasets from the warm season (May-September) of 2021-2023: North China regional mosaic composite reflectivity radar products, single-site radar data from Northern Shanxi, ERA5 reanalysis data, and surface observation data. Statistical analyses were conducted on the changing characteristics of squall lines descending mountains in this region, yielding the following main conclusions: (1) A total of 29 squall lines were identified. Based on their direction of movement, they were classified into four types: west-moving, northwest-moving, north-moving, and basin-originating. Based on their intensity change upon descending mountains, they were classified into three types: intensifying, weakening, and maintaining types. The weakening type was the most common, accounting for 67%. It was also found that all west-moving squall lines belonged to the weakening type upon descent, while all north-moving types were intensifying. The northwest-moving type included squall lines that intensified, weakened, or maintained their intensity upon descent. (2) Analysis of the environmental background ahead of the descending path for intensifying and weakening types within the northwest-moving squall lines revealed that, compared to weakening squall lines, intensifying ones exhibited slightly stronger dynamic conditions (850 hPa divergence), while conditions related to moisture (850 hPa specific humidity, atmospheric total column precipitable water), convective available potential energy (CAPE), and vertical wind shear were comparable or slightly poorer. This suggests that changes in squall line intensity upon descent may be driven more by their internal dynamics (such as the balance between the cold pool and inflow) rather than static environmental conditions. Consequently, accurately predicting whether a squall line will intensify or weaken upon descent based solely on the environmental conditions ahead of its path is difficult. (3) For short-term nowcasting, radar data can be used to predict whether a squall line will intensify or weaken upon descent.?Intensifying squall lines?upon descent typically exhibit stronger echo intensity, a movement speed around 17 m·s?1, large gradient zones of reflectivity factor concentrated at the leading edge, an overall bow-shaped morphology accompanied by a gust front. Radial velocity cross-sections show a distinct organized structure with forward inflow ascending slantwise along the rear inflow.?Weakening squall lines?upon descent typically exhibit weak to moderate echo intensity, a movement speed below 10 m·s?1, large gradient zones of reflectivity factor concentrated at the rear, a relatively straight overall morphology without an accompanying gust front, and radial velocity cross-sections lacking a distinct organized structure with forward inflow ascending slantwise along the rear inflow.
In order to systematically investigate the evolution characteristics and mechanisms of squall lines descending mountains in Northern Shanxi, this study utilized the following datasets from the warm season (May-September) of 2021-2023: North China regional mosaic composite reflectivity radar products, single-site radar data from Northern Shanxi, ERA5 reanalysis data, and surface observation data. Statistical analyses were conducted on the changing characteristics of squall lines descending mountains in this region, yielding the following main conclusions: (1) A total of 29 squall lines were identified. Based on their direction of movement, they were classified into four types: west-moving, northwest-moving, north-moving, and basin-originating. Based on their intensity change upon descending mountains, they were classified into three types: intensifying, weakening, and maintaining types. The weakening type was the most common, accounting for 67%. It was also found that all west-moving squall lines belonged to the weakening type upon descent, while all north-moving types were intensifying. The northwest-moving type included squall lines that intensified, weakened, or maintained their intensity upon descent. (2) Analysis of the environmental background ahead of the descending path for intensifying and weakening types within the northwest-moving squall lines revealed that, compared to weakening squall lines, intensifying ones exhibited slightly stronger dynamic conditions (850 hPa divergence), while conditions related to moisture (850 hPa specific humidity, atmospheric total column precipitable water), convective available potential energy (CAPE), and vertical wind shear were comparable or slightly poorer. This suggests that changes in squall line intensity upon descent may be driven more by their internal dynamics (such as the balance between the cold pool and inflow) rather than static environmental conditions. Consequently, accurately predicting whether a squall line will intensify or weaken upon descent based solely on the environmental conditions ahead of its path is difficult. (3) For short-term nowcasting, radar data can be used to predict whether a squall line will intensify or weaken upon descent.?Intensifying squall lines?upon descent typically exhibit stronger echo intensity, a movement speed around 17 m·s?1, large gradient zones of reflectivity factor concentrated at the leading edge, an overall bow-shaped morphology accompanied by a gust front. Radial velocity cross-sections show a distinct organized structure with forward inflow ascending slantwise along the rear inflow.?Weakening squall lines?upon descent typically exhibit weak to moderate echo intensity, a movement speed below 10 m·s?1, large gradient zones of reflectivity factor concentrated at the rear, a relatively straight overall morphology without an accompanying gust front, and radial velocity cross-sections lacking a distinct organized structure with forward inflow ascending slantwise along the rear inflow.
Available online: December 23, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.091601
Abstract:
Using historical thunderstorm gale cases in the Sichuan Basin from March 1 to September 30 during 2018–2022, combined with 3D radar mosaic data and surface maximum wind observations, we constructed a thunderstorm gale sample dataset and developed a grid-based gale warning model. Independent validation was conducted for 2023 thunderstorm gale events to evaluate the model’s warning performance. The main conclusions are as follows:(1) The LightGBM model achieved the highest probability of detection (POD, 0.536 at 15-minute lead time with a 10 km evaluation radius), but also exhibited the highest false alarm ratio (FAR). The random forest (RF) model demonstrated the best overall performance, with the highest critical success index (CSI, 0.306 at 30-minute lead time and 10 km radius). Both CSI and POD scores decreased significantly with longer lead times or smaller evaluation radii, particularly when the lead time extended from 30 to 45 minutes.(2) Synoptic background significantly influenced warning effectiveness, Under strong cold air influence, factors such as composite reflectivity (CR), echo top (TOP), and 45dBZ echo top height (H45) were more likely to reach high values, favoring intense convective development. However, newly initiated storms at convective fronts tended to increase missed detections. In the absence of strong cold air, thunderstorm gales primarily occurred at the leading edge of convective systems, resulting in higher POD.(3) The temporal variation of vertically integrated liquid water (VIL) contributed most to model decisions, followed by vertical liquid water density (VILD), echo top height, and maximum reflectivity (maxZ), highlighting deep convection as the core mechanism of thunderstorm gales. In cold air-absent scenarios, downdrafts dominated the warning process. Analysis of key feature values and high SHAP values revealed that temporal changes in convective echoes were critical for warnings. Samples with strong TREC wind fields often corresponded to positive SHAP values, indicating increased probability of convective gales when echo motion accelerates.
Using historical thunderstorm gale cases in the Sichuan Basin from March 1 to September 30 during 2018–2022, combined with 3D radar mosaic data and surface maximum wind observations, we constructed a thunderstorm gale sample dataset and developed a grid-based gale warning model. Independent validation was conducted for 2023 thunderstorm gale events to evaluate the model’s warning performance. The main conclusions are as follows:(1) The LightGBM model achieved the highest probability of detection (POD, 0.536 at 15-minute lead time with a 10 km evaluation radius), but also exhibited the highest false alarm ratio (FAR). The random forest (RF) model demonstrated the best overall performance, with the highest critical success index (CSI, 0.306 at 30-minute lead time and 10 km radius). Both CSI and POD scores decreased significantly with longer lead times or smaller evaluation radii, particularly when the lead time extended from 30 to 45 minutes.(2) Synoptic background significantly influenced warning effectiveness, Under strong cold air influence, factors such as composite reflectivity (CR), echo top (TOP), and 45dBZ echo top height (H45) were more likely to reach high values, favoring intense convective development. However, newly initiated storms at convective fronts tended to increase missed detections. In the absence of strong cold air, thunderstorm gales primarily occurred at the leading edge of convective systems, resulting in higher POD.(3) The temporal variation of vertically integrated liquid water (VIL) contributed most to model decisions, followed by vertical liquid water density (VILD), echo top height, and maximum reflectivity (maxZ), highlighting deep convection as the core mechanism of thunderstorm gales. In cold air-absent scenarios, downdrafts dominated the warning process. Analysis of key feature values and high SHAP values revealed that temporal changes in convective echoes were critical for warnings. Samples with strong TREC wind fields often corresponded to positive SHAP values, indicating increased probability of convective gales when echo motion accelerates.
Available online: December 04, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.072401
Abstract:
Based on ground meteorological and environmental monitoring station data, O3 meteorological condition evaluation index, O3 Source apportionment products, OMI remote sensing data, GDAS and other data, combined with HYSPLIT model and other methods, the spatiotemporal variation characteristics of O3 pollution in Shaanxi from May to October 2019 to 2023 were analyzed. The impact of meteorological conditions on O3 concentration changes was quantitatively evaluated, and the local and transmission contributions of O3 pollution, as well as the contributions of different precursors, were quantitatively separated. Finally, the pollution transmission path was explored. The results show that in the warm season of 2022, O3 pollution in Shaanxi is the heaviest, and in 2020, the pollution is the lightest. The O3 concentration shows a typical unimodal monthly and daily variation, with a monthly peak occurring in June, a daily maximum occurring from 15:00 to 16:00, and a minimum occurring at 7:00. The O3 concentration on non working days is lower than that on working days. The O3 pollution in Guanzhong is the heaviest, and the pollution is mainly concentrated in the inner layer of the trumpet mouth terrain in the Guanzhong Plain, with the lightest in southern Shaanxi. From May to October 2022, the daily average total radiation exposure in Shaanxi is the highest (17.28MJ/m2), the daily maximum temperature is the highest (27.7℃), the number of precipitation days is the lowest (56d), and the sunshine duration is relatively long (6.4h). The O3 comprehensive meteorological conditions are the worst, which is the main reason for the heaviest O3 pollution in Shaanxi in 2022. From May to October 2022, the O3 concentration in Shaanxi increases by 8.1% compared to the same period last year, and meteorological conditions can increase it by 7.7% compared to the same period last year. If the emission source remains unchanged, the O3 concentration in Shaanxi Province from May to October 2020 should have increased by 4.4% compared to the same period in 2019, but the actual O3 concentration has decreased by 5.3%, which fully reflects the positive effects of regional air pollution control. The O3 comprehensive meteorological conditions in northern Shaanxi are the worst, but the O3 concentration in Guanzhong is the highest, which is mainly related to the high emissions of O3 precursors and regional transportation in Guanzhong. From May to October 2023, the concentration of O3 in Shaanxi Province is mainly affected by precursor NOx, and the contribution of external transport (45%) is greater than that of local transport (17%). The main transport pathway is in the southeast, with Henan and Hubei provinces having the greatest impact on Shaanxi transport, contributing 6% and 4% respectively.
Based on ground meteorological and environmental monitoring station data, O3 meteorological condition evaluation index, O3 Source apportionment products, OMI remote sensing data, GDAS and other data, combined with HYSPLIT model and other methods, the spatiotemporal variation characteristics of O3 pollution in Shaanxi from May to October 2019 to 2023 were analyzed. The impact of meteorological conditions on O3 concentration changes was quantitatively evaluated, and the local and transmission contributions of O3 pollution, as well as the contributions of different precursors, were quantitatively separated. Finally, the pollution transmission path was explored. The results show that in the warm season of 2022, O3 pollution in Shaanxi is the heaviest, and in 2020, the pollution is the lightest. The O3 concentration shows a typical unimodal monthly and daily variation, with a monthly peak occurring in June, a daily maximum occurring from 15:00 to 16:00, and a minimum occurring at 7:00. The O3 concentration on non working days is lower than that on working days. The O3 pollution in Guanzhong is the heaviest, and the pollution is mainly concentrated in the inner layer of the trumpet mouth terrain in the Guanzhong Plain, with the lightest in southern Shaanxi. From May to October 2022, the daily average total radiation exposure in Shaanxi is the highest (17.28MJ/m2), the daily maximum temperature is the highest (27.7℃), the number of precipitation days is the lowest (56d), and the sunshine duration is relatively long (6.4h). The O3 comprehensive meteorological conditions are the worst, which is the main reason for the heaviest O3 pollution in Shaanxi in 2022. From May to October 2022, the O3 concentration in Shaanxi increases by 8.1% compared to the same period last year, and meteorological conditions can increase it by 7.7% compared to the same period last year. If the emission source remains unchanged, the O3 concentration in Shaanxi Province from May to October 2020 should have increased by 4.4% compared to the same period in 2019, but the actual O3 concentration has decreased by 5.3%, which fully reflects the positive effects of regional air pollution control. The O3 comprehensive meteorological conditions in northern Shaanxi are the worst, but the O3 concentration in Guanzhong is the highest, which is mainly related to the high emissions of O3 precursors and regional transportation in Guanzhong. From May to October 2023, the concentration of O3 in Shaanxi Province is mainly affected by precursor NOx, and the contribution of external transport (45%) is greater than that of local transport (17%). The main transport pathway is in the southeast, with Henan and Hubei provinces having the greatest impact on Shaanxi transport, contributing 6% and 4% respectively.
Available online: December 01, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.111801
Abstract:
In response to the issue of insufficient accuracy in identifying tornadoes using conventional threshold methods,this study proposes a machine learning-based tornado identification method driven by multiple radar-derived storm features. The method first calculates and constructs a storm feature dataset based on radar base data from tornado cases in China between 2003 and 2023. The dataset includes three categories: (1) tornadic storms, (2) non-tornadic storms with significant three-dimensional vortex signature(3DVS), and (3) non-tornadic storms without significant 3DVS. Feature importance ranking is then performed using XGBoost, and the top 14 features are selected as model inputs after combining with PCA. A TFM+CNN deep learning model for tornado recognition is constructed by using the encoder part of the TFM architecture and utilizing CNN to increase the input vector dimension and adding multiple fully connected layers at the end of the model. Three binary classification experiments are conducted using this model: (1) tornado storms vs. non-tornadic storms without significant 3DVS, (2) tornado storms vs. non-tornadic storms with significant 3DVS, and (3) tornado storms vs. non-tornadic storms. Comparative experiments with the XGBoost model are also performed. The results show that the TFM+CNN model achieves CSI values of 84%, 71%, and 73%; POD values of 94%, 83%, and 83%; and FAR values of 11%, 16%, and 14% in the three binary classification experiments, respectively. Compared to the XGBoost model, the TFM+CNN model performs better in most metrics, except for a 5% higher FAR in experiments 1 and 3. Both models exhibit the worst performance in experiment 2. Both models performed worst in experiment 2, indicating that tornadic storms and non-tornadic storms with significant 3DVS are the most challenging to distinguish. Furthermore, the TFM+CNN model has a larger AUC under ROC, indicating stronger generalization ability. It can be seen that the TFM+CNN model has strong tornado recognition ability.
In response to the issue of insufficient accuracy in identifying tornadoes using conventional threshold methods,this study proposes a machine learning-based tornado identification method driven by multiple radar-derived storm features. The method first calculates and constructs a storm feature dataset based on radar base data from tornado cases in China between 2003 and 2023. The dataset includes three categories: (1) tornadic storms, (2) non-tornadic storms with significant three-dimensional vortex signature(3DVS), and (3) non-tornadic storms without significant 3DVS. Feature importance ranking is then performed using XGBoost, and the top 14 features are selected as model inputs after combining with PCA. A TFM+CNN deep learning model for tornado recognition is constructed by using the encoder part of the TFM architecture and utilizing CNN to increase the input vector dimension and adding multiple fully connected layers at the end of the model. Three binary classification experiments are conducted using this model: (1) tornado storms vs. non-tornadic storms without significant 3DVS, (2) tornado storms vs. non-tornadic storms with significant 3DVS, and (3) tornado storms vs. non-tornadic storms. Comparative experiments with the XGBoost model are also performed. The results show that the TFM+CNN model achieves CSI values of 84%, 71%, and 73%; POD values of 94%, 83%, and 83%; and FAR values of 11%, 16%, and 14% in the three binary classification experiments, respectively. Compared to the XGBoost model, the TFM+CNN model performs better in most metrics, except for a 5% higher FAR in experiments 1 and 3. Both models exhibit the worst performance in experiment 2. Both models performed worst in experiment 2, indicating that tornadic storms and non-tornadic storms with significant 3DVS are the most challenging to distinguish. Furthermore, the TFM+CNN model has a larger AUC under ROC, indicating stronger generalization ability. It can be seen that the TFM+CNN model has strong tornado recognition ability.
Available online: November 25, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.091301
Abstract:
The first comprehensive observation with multi-source remote sensing detection equipment for convective cloud precipitation on the northern slope of Mount Everest about 6 years in order to research the characteristics of convective cloud precipitation in Mount Everest region(MER) was reported in this paper based on the second comprehensive scientific investigation and research plan of the Tibetan Plateau. The first observation experiment with multi-source remote sensing detection equipment for studying convective cloud precipitation in the MER from 2019 to 2024, revealing the unique mechanism triggering summer convective cloud precipitation and the spatial and temporal evolution of its macro- and micro-scale physical structural characteristics. Multi-source detection equipment, including X-band dual-polarization Doppler weather radar, ground automatic stations, 2D video disdrometers, microwave radiometers and radio sounding, were employed to construct an observation network. Various methods such data quality control, data retrieval and data statistics based on the observation network data were adopted to carry out comparative analysis experiments，the research results show that the MER has unique structural characteristics of convective cloud precipitation compared with other regions as following: In terms of macroscopic characteristics, precipitation occurs frequently but with a short duration. Most of them are isolated convective cells, and the horizontal scale and vertical extension thickness of precipitation are much smaller than in other areas, and rainfall rate is weak in the boundary layer. In terms of microscopic characteristics, there are two phases of precipitation in the boundary layer under different conditions of atmospheric temperature vertical profile distribution: graupel and liquid raindrops, with distinctive characteristics of a narrow raindrop spectrum distribution width and higher raindrop number concentration and small raindrop equivalent diameter. The internal physical mechanism underlying the influence of the northern slope on summer convective cloud precipitation in the MER is that the extremely high elevation, complex topography, summer South Asian monsoon and intense solar radiation jointly promote the formation of intense thermal vertical motion throughout the troposphere and weak dynamic uplift and poor water vapor conditions in the boundary layer. This study may bridge the gap in detailed observations of the weather structure of the convective cloud precipitation for the northern slope of the MER in summer and provide a significant reference for further studies of Tibetan Plateau weather changes and their potential impacts on the East Asian climate.
The first comprehensive observation with multi-source remote sensing detection equipment for convective cloud precipitation on the northern slope of Mount Everest about 6 years in order to research the characteristics of convective cloud precipitation in Mount Everest region(MER) was reported in this paper based on the second comprehensive scientific investigation and research plan of the Tibetan Plateau. The first observation experiment with multi-source remote sensing detection equipment for studying convective cloud precipitation in the MER from 2019 to 2024, revealing the unique mechanism triggering summer convective cloud precipitation and the spatial and temporal evolution of its macro- and micro-scale physical structural characteristics. Multi-source detection equipment, including X-band dual-polarization Doppler weather radar, ground automatic stations, 2D video disdrometers, microwave radiometers and radio sounding, were employed to construct an observation network. Various methods such data quality control, data retrieval and data statistics based on the observation network data were adopted to carry out comparative analysis experiments，the research results show that the MER has unique structural characteristics of convective cloud precipitation compared with other regions as following: In terms of macroscopic characteristics, precipitation occurs frequently but with a short duration. Most of them are isolated convective cells, and the horizontal scale and vertical extension thickness of precipitation are much smaller than in other areas, and rainfall rate is weak in the boundary layer. In terms of microscopic characteristics, there are two phases of precipitation in the boundary layer under different conditions of atmospheric temperature vertical profile distribution: graupel and liquid raindrops, with distinctive characteristics of a narrow raindrop spectrum distribution width and higher raindrop number concentration and small raindrop equivalent diameter. The internal physical mechanism underlying the influence of the northern slope on summer convective cloud precipitation in the MER is that the extremely high elevation, complex topography, summer South Asian monsoon and intense solar radiation jointly promote the formation of intense thermal vertical motion throughout the troposphere and weak dynamic uplift and poor water vapor conditions in the boundary layer. This study may bridge the gap in detailed observations of the weather structure of the convective cloud precipitation for the northern slope of the MER in summer and provide a significant reference for further studies of Tibetan Plateau weather changes and their potential impacts on the East Asian climate.
Available online: November 19, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.071701
Abstract:
Low-altitude flight activities are highly susceptible to complex wind fields, leading civil aviation meteorological departments to place significant emphasis on refined monitoring and early warning technologies for low-altitude winds. This study analyzes a cold front strong wind at Guanghan Airport on December 26, 2021, using Doppler wind lidar, airport automatic observation equipment, and reanalysis data. The results indicate that the Doppler wind lidar can clearly show that during the influence of cold air, surface strong winds occur approximately 4-6 hours after the low-level jet weakens, with significant non-uniformity in downward momentum transfer and vertical motion changes. Subsidence enhances the downward momentum transfer of the Low-level jet, resulting in increased surface wind speeds, while upward motion hinders downward momentum transfer, leading to intermittent surface strong winds. The 12° PPI scanning of the Doppler wind lidar can provide early warnings of potential strong winds along the glide path and at the surface 1-1.5 hours in advance. The intrusion of residual cold air behind the front caused a secondary wind event, which should be monitored when forecasting strong winds. This study demonstrates that Doppler wind lidar significantly enhances the monitoring precision of low-altitude wind field evolution, providing valuable insights for ensuring the safety and efficiency of low-altitude flight operations.
Low-altitude flight activities are highly susceptible to complex wind fields, leading civil aviation meteorological departments to place significant emphasis on refined monitoring and early warning technologies for low-altitude winds. This study analyzes a cold front strong wind at Guanghan Airport on December 26, 2021, using Doppler wind lidar, airport automatic observation equipment, and reanalysis data. The results indicate that the Doppler wind lidar can clearly show that during the influence of cold air, surface strong winds occur approximately 4-6 hours after the low-level jet weakens, with significant non-uniformity in downward momentum transfer and vertical motion changes. Subsidence enhances the downward momentum transfer of the Low-level jet, resulting in increased surface wind speeds, while upward motion hinders downward momentum transfer, leading to intermittent surface strong winds. The 12° PPI scanning of the Doppler wind lidar can provide early warnings of potential strong winds along the glide path and at the surface 1-1.5 hours in advance. The intrusion of residual cold air behind the front caused a secondary wind event, which should be monitored when forecasting strong winds. This study demonstrates that Doppler wind lidar significantly enhances the monitoring precision of low-altitude wind field evolution, providing valuable insights for ensuring the safety and efficiency of low-altitude flight operations.
Available online: October 17, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.101301
Abstract:
To enhance the forecasting capability for flash heavy rain (FHR) in the Beijing Daxing International Airport (PKX) region, this study utilizes minute- and hourly-level data from May to September during 2014—2023, combined with ERA5 reanalysis data, to classify circulation patterns and analyze the precipitation and then temporal-spatial distribution characteristics and environmental conditions. The results show that FHR processes are classified into five circulation patterns, listing in descending order of their percentage as follows: the Mongolian Cyclone and Trough Type, the Western Pacific Subtropical High Edge Type, the Interaction Type of Westerly Trough and Western Pacific Subtropical High, the Huang-Huai Cyclone Inverted Trough Type, and the Northeastern China Cold Vortex Rear Type. The annual average frequency of FHR is relatively higher in the eastern region near PKX, showing a fluctuating but upward trend over the past decade. FHR events are most frequent in July and August, with July accounting for more than half of the occurrences. The diurnal variation exhibits a unimodal distribution, peaking at 22:00—23:00 BT, with durations generally ranging from 40 to 80 min. The Western Pacific Subtropical High Edge Type, the Interaction Type of Westerly Trough and Western Pacific Subtropical High, and the Northeastern China Cold Vortex Rear Type display distinct temporal characteristics, with the former two being predominantly nocturnal and the latter occurring more frequently in the afternoon. Intense flash heavy rain (≥50 mm·h?1) primarily occurs under Western Pacific Subtropical High Edge Type, and Mongolian Cyclone and Trough Type. Significant differences are observed in the environmental conditions under different circulation patterns. The Western Pacific Subtropical High Edge Type, Interaction Type of Westerly Trough and Western Pacific Subtropical High, and the Huang-Huai Cyclone Inverted Trough Type are characterized by abundant moisture, with total precipitable water vapor exceeding 50 mm and high convective available potential energy (CAPE), whereas the Huang-Huai Cyclone Inverted Trough Type exhibits strong moisture convergence despite weaker thermal instability, often featuring boundary-layer easterly jets that sustain precipitation. The Northeastern China Cold Vortex Rear Type, despite limited column moisture, favors localized heavy rainfall through strong low-level warm advection and significant upper-lower atmospheric temperature differences, favoring the development of localized heavy rainfall.
To enhance the forecasting capability for flash heavy rain (FHR) in the Beijing Daxing International Airport (PKX) region, this study utilizes minute- and hourly-level data from May to September during 2014—2023, combined with ERA5 reanalysis data, to classify circulation patterns and analyze the precipitation and then temporal-spatial distribution characteristics and environmental conditions. The results show that FHR processes are classified into five circulation patterns, listing in descending order of their percentage as follows: the Mongolian Cyclone and Trough Type, the Western Pacific Subtropical High Edge Type, the Interaction Type of Westerly Trough and Western Pacific Subtropical High, the Huang-Huai Cyclone Inverted Trough Type, and the Northeastern China Cold Vortex Rear Type. The annual average frequency of FHR is relatively higher in the eastern region near PKX, showing a fluctuating but upward trend over the past decade. FHR events are most frequent in July and August, with July accounting for more than half of the occurrences. The diurnal variation exhibits a unimodal distribution, peaking at 22:00—23:00 BT, with durations generally ranging from 40 to 80 min. The Western Pacific Subtropical High Edge Type, the Interaction Type of Westerly Trough and Western Pacific Subtropical High, and the Northeastern China Cold Vortex Rear Type display distinct temporal characteristics, with the former two being predominantly nocturnal and the latter occurring more frequently in the afternoon. Intense flash heavy rain (≥50 mm·h?1) primarily occurs under Western Pacific Subtropical High Edge Type, and Mongolian Cyclone and Trough Type. Significant differences are observed in the environmental conditions under different circulation patterns. The Western Pacific Subtropical High Edge Type, Interaction Type of Westerly Trough and Western Pacific Subtropical High, and the Huang-Huai Cyclone Inverted Trough Type are characterized by abundant moisture, with total precipitable water vapor exceeding 50 mm and high convective available potential energy (CAPE), whereas the Huang-Huai Cyclone Inverted Trough Type exhibits strong moisture convergence despite weaker thermal instability, often featuring boundary-layer easterly jets that sustain precipitation. The Northeastern China Cold Vortex Rear Type, despite limited column moisture, favors localized heavy rainfall through strong low-level warm advection and significant upper-lower atmospheric temperature differences, favoring the development of localized heavy rainfall.
Available online: October 17, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.101501
Abstract:
On the night of July 12, 2023, the vicinity of Feixian County, Shandong Province was affected by supercell heavy precipitation, resulting in a rare extreme rainstorm event. This paper comprehensively utilized multi-source observational data and ERA5 reanalysis data to deeply explore the circulation background of this extreme precipitation, the coupling mechanism of high and low-level jets, the activity characteristics of meso- and small-scale weather systems, and the microphysical characteristics of precipitation. The research shows that: (1) Favorable circulation patterns, environmental wind fields, and water vapor transport provided large-scale background conditions for the occurrence of short-term heavy precipitation. The thickness of the warm cloud layer and the maximum liquid water mixing ratio content were well correlated with the extreme heavy precipitation period. During the extreme heavy precipitation period, the warm cloud layer thickened rapidly, and the high-humidity area lasted for a long time. The enhanced cloud water content and the thickened saturated moist layer provided the prerequisite conditions for the formation of efficient precipitation. (2) The rapidly developing boundary layer jet (SW-BLJ) and the synoptic-scale low-level jet (SW-LLJ) overlapped and coupled vertically in southern Shandong Province, which promoted the extreme short-term heavy precipitation near Shangzhuang, Feixian County on the night of the 12th. The extreme rainfall intensity occurred in the left front side of the overlapping area of the double low-level jets from 21:00 to 22:00. (3) This precipitation process was affected by the synergistic action of multi-scale systems. The surface mesoscale convergence line triggered and promoted the occurrence and development of convective cells. The presence of a mesocyclone at the low level of the supercell strengthened the small-scale convergent upward motion, significantly increasing the precipitation. (4) This extreme short-term heavy precipitation had the characteristics of a mixed type of tropical oceanic and continental convective precipitation. At the beginning of precipitation, the raindrop spectrum changed significantly, manifested as a sharp increase in raindrop number concentration and a significant increase in raindrop diameter. Small and medium raindrops accounted for the majority, and the proportion of small particles with Dm < 2 mm was close to 85 %. The number of large raindrops increased with the increase in rainfall intensity. In terms of the contribution rate to precipitation, although medium particles with a diameter of 2 - 3 mm only accounted for 11.77 %, they contributed the most to precipitation. Followed by small particles with a diameter of 1 - 2 mm. Although the proportion of larger particles with a diameter of 3 - 4 mm was small, accounting for 2.947 %, their contribution also accounted for 23.108 %. Although the number of small particles with Dm < 1 mm was large, accounting for 43.354 %, their contribution was less than 4 %.
On the night of July 12, 2023, the vicinity of Feixian County, Shandong Province was affected by supercell heavy precipitation, resulting in a rare extreme rainstorm event. This paper comprehensively utilized multi-source observational data and ERA5 reanalysis data to deeply explore the circulation background of this extreme precipitation, the coupling mechanism of high and low-level jets, the activity characteristics of meso- and small-scale weather systems, and the microphysical characteristics of precipitation. The research shows that: (1) Favorable circulation patterns, environmental wind fields, and water vapor transport provided large-scale background conditions for the occurrence of short-term heavy precipitation. The thickness of the warm cloud layer and the maximum liquid water mixing ratio content were well correlated with the extreme heavy precipitation period. During the extreme heavy precipitation period, the warm cloud layer thickened rapidly, and the high-humidity area lasted for a long time. The enhanced cloud water content and the thickened saturated moist layer provided the prerequisite conditions for the formation of efficient precipitation. (2) The rapidly developing boundary layer jet (SW-BLJ) and the synoptic-scale low-level jet (SW-LLJ) overlapped and coupled vertically in southern Shandong Province, which promoted the extreme short-term heavy precipitation near Shangzhuang, Feixian County on the night of the 12th. The extreme rainfall intensity occurred in the left front side of the overlapping area of the double low-level jets from 21:00 to 22:00. (3) This precipitation process was affected by the synergistic action of multi-scale systems. The surface mesoscale convergence line triggered and promoted the occurrence and development of convective cells. The presence of a mesocyclone at the low level of the supercell strengthened the small-scale convergent upward motion, significantly increasing the precipitation. (4) This extreme short-term heavy precipitation had the characteristics of a mixed type of tropical oceanic and continental convective precipitation. At the beginning of precipitation, the raindrop spectrum changed significantly, manifested as a sharp increase in raindrop number concentration and a significant increase in raindrop diameter. Small and medium raindrops accounted for the majority, and the proportion of small particles with Dm < 2 mm was close to 85 %. The number of large raindrops increased with the increase in rainfall intensity. In terms of the contribution rate to precipitation, although medium particles with a diameter of 2 - 3 mm only accounted for 11.77 %, they contributed the most to precipitation. Followed by small particles with a diameter of 1 - 2 mm. Although the proportion of larger particles with a diameter of 3 - 4 mm was small, accounting for 2.947 %, their contribution also accounted for 23.108 %. Although the number of small particles with Dm < 1 mm was large, accounting for 43.354 %, their contribution was less than 4 %.
Available online: October 13, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.071601
Abstract:
The differential reflectivity (ZDR) column is a radar observation feature capable of indicating severe convective weather, but it is still not used extensively to inform warning decisions. To address this research focus, radar data features and hailstorm warning studies are conducted via the cold layer composite differential reflectivity (CZDRC) map and the ZDR echo area time?height plot on the basis of three hailstorm cases observed in Shandong Province in recent years. The results indicate that even when the radar echo area is relatively small, a 3 dB ZDR column feature can be observed within the cloud near the hailfall points in the CZDRC map. The ZDR column feature appears 20–40 minutes before the first hailfall time during a hail event, which is 10–20 minutes earlier than the traditional way by using 45 dBZ or 55 dBZ reflectivity threshold, indicating its potential as an early warning indicator for hailstorms. Weather radars of different wavelengths and scanning systems, including X-band dual-polarization phased-array radar (X-PAR), S-band, and C-band radars, present the ZDR column feature necessary for strong convective weather warnings in both the CZDRC map and ZDR echo area time?height plot. Additionally, the ZDR column feature on the CZDRC map is closely situated and surrounds the hailfall points in all three case studies. These ZDR column features are located northwest of the hailfall points, which are in the mid-tropospheric upwind direction, and could serve as a reference for identifying hail locations.
The differential reflectivity (ZDR) column is a radar observation feature capable of indicating severe convective weather, but it is still not used extensively to inform warning decisions. To address this research focus, radar data features and hailstorm warning studies are conducted via the cold layer composite differential reflectivity (CZDRC) map and the ZDR echo area time?height plot on the basis of three hailstorm cases observed in Shandong Province in recent years. The results indicate that even when the radar echo area is relatively small, a 3 dB ZDR column feature can be observed within the cloud near the hailfall points in the CZDRC map. The ZDR column feature appears 20–40 minutes before the first hailfall time during a hail event, which is 10–20 minutes earlier than the traditional way by using 45 dBZ or 55 dBZ reflectivity threshold, indicating its potential as an early warning indicator for hailstorms. Weather radars of different wavelengths and scanning systems, including X-band dual-polarization phased-array radar (X-PAR), S-band, and C-band radars, present the ZDR column feature necessary for strong convective weather warnings in both the CZDRC map and ZDR echo area time?height plot. Additionally, the ZDR column feature on the CZDRC map is closely situated and surrounds the hailfall points in all three case studies. These ZDR column features are located northwest of the hailfall points, which are in the mid-tropospheric upwind direction, and could serve as a reference for identifying hail locations.
Available online: September 23, 2025 , DOI: 10.7519/j.issn.1000-0526.2024.123101
Abstract:
From April 9th to 15th, 2023 (Beijing Time, the same below), a six-day sandstorm weather event occurred in Beijing-Tianjin-Hebei, causing an irradiance loss rate of 10-12.5%, which had a certain impact on photovoltaic power generation. Utilizing conventional meteorological data, reanalysis data, and new detection methods such as wind profiler radar and lidar, this study analyzed the characteristics and maintenance mechanisms of the sandstorm weather in Beijing-Tianjin-Hebei, as well as its impact on the irradiance loss rate. The results show that the six-day sandstorm weather in Beijing-Tianjin-Hebei was directly related to three rapidly moving weather systems, primarily influenced by the Mongolian cyclone, two cold fronts, and southerly airflow. During the Mongolian cyclone phase, sand originated from southern Mongolia and was lifted and transported along the 700hPa jet stream axis, forming near-surface blowing sand or floating dust through dry deposition. In the cold front phase, extensive dust sources and the passage of a surface cold front caused a rapid increase in surface wind speed, lifting large amounts of dust which then traveled to Beijing-Tianjin-Hebei along the low-level jet in the troposphere and was rapidly transported to the surface with the descending airflow behind the cold front. During the southerly airflow phase, influenced by the return of dust sources from the middle and lower reaches of the Yangtze River, dust was continuously transported northward under the action of the southerly airflow behind the surface high pressure system, reaching relatively low altitudes and mainly forming blowing sand or floating dust through dry deposition at the surface. Sandstorm characteristics varied under the influence of different systems: During the Mongolian cyclone phase, the sandstorm had a weaker impact but a higher upper boundary height; during the cold front phase, dust concentrations were high and visibility low, with a sandstorm occurring two hours after the cold front"s passage and lasting for two hours, followed by clean air 13 hours later; during the southerly airflow phase, the sandstorm lasted longer but was the weakest in intensity. Calculations revealed that during this sandstorm event, the irradiance loss rate had a greater correlation with the cumulative dust content than with the instantaneous dust content. The local turbulence dissipation rate increased three hours earlier than the dust concentration, providing valuable indications for sandstorm monitoring and forecasting. The above analysis results offer valuable reference for future forecasting of sandstorm weather and its impact on photovoltaic power generation.
From April 9th to 15th, 2023 (Beijing Time, the same below), a six-day sandstorm weather event occurred in Beijing-Tianjin-Hebei, causing an irradiance loss rate of 10-12.5%, which had a certain impact on photovoltaic power generation. Utilizing conventional meteorological data, reanalysis data, and new detection methods such as wind profiler radar and lidar, this study analyzed the characteristics and maintenance mechanisms of the sandstorm weather in Beijing-Tianjin-Hebei, as well as its impact on the irradiance loss rate. The results show that the six-day sandstorm weather in Beijing-Tianjin-Hebei was directly related to three rapidly moving weather systems, primarily influenced by the Mongolian cyclone, two cold fronts, and southerly airflow. During the Mongolian cyclone phase, sand originated from southern Mongolia and was lifted and transported along the 700hPa jet stream axis, forming near-surface blowing sand or floating dust through dry deposition. In the cold front phase, extensive dust sources and the passage of a surface cold front caused a rapid increase in surface wind speed, lifting large amounts of dust which then traveled to Beijing-Tianjin-Hebei along the low-level jet in the troposphere and was rapidly transported to the surface with the descending airflow behind the cold front. During the southerly airflow phase, influenced by the return of dust sources from the middle and lower reaches of the Yangtze River, dust was continuously transported northward under the action of the southerly airflow behind the surface high pressure system, reaching relatively low altitudes and mainly forming blowing sand or floating dust through dry deposition at the surface. Sandstorm characteristics varied under the influence of different systems: During the Mongolian cyclone phase, the sandstorm had a weaker impact but a higher upper boundary height; during the cold front phase, dust concentrations were high and visibility low, with a sandstorm occurring two hours after the cold front"s passage and lasting for two hours, followed by clean air 13 hours later; during the southerly airflow phase, the sandstorm lasted longer but was the weakest in intensity. Calculations revealed that during this sandstorm event, the irradiance loss rate had a greater correlation with the cumulative dust content than with the instantaneous dust content. The local turbulence dissipation rate increased three hours earlier than the dust concentration, providing valuable indications for sandstorm monitoring and forecasting. The above analysis results offer valuable reference for future forecasting of sandstorm weather and its impact on photovoltaic power generation.
Available online: September 12, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.090901
Abstract:
Accounting for the value of climate ecological products based on climate resources is an important branch of the accounting system of gross ecosystem product (GEP), which is of great scientific value in solving the bottleneck of the system of "difficult to measure and difficult to mortgage" of climate resources. It is of key scientific significance in promoting the asset-based management of climate resources and realizing the value of ecological products. In this study, Fengjie County in Chongqing Municipality, is used as a case study to explore the construction of a gross climate ecosystem product (GEPC) accounting system from the perspective of the contribution of climate to ecological products. Utilizing meteorological, ecological environment and socio-economic data, we established an accounting framework of 12 specific indexes containing the three major functions of climate supply products, climate regulation services, and climate cultural services, and systematically assessed the value of climate ecosystem products in Fengjie County, Chongqing Municipality, from 2019 to 2023. The results show that the annual mean value of GEPC in Fengjie County in 2019–2023 is 17.17 billion yuan, accounting for 48% of GDP; the structural characteristics are dominated by "climate regulation" (57.0% of the value of climate regulation services > 38.5% of the value of climate supply products >4.4% of the value of climate cultural services). The GEPC fluctuates from 13.92 billion yuan to 20.95 billion yuan between years, with the peak year (2023) being 1.5 times the lowest years (2019). The ratio of GEPC to GDP in Fengjie County ranges from 0.36 to 0.56 (mean value 0.48) in 2019–2023, with reference to the Green Gold Index, which reflects to some extent the dynamic coupling of the transformation of the value of climatic resources and the level of economic development. Fengjie County has a per capita GEPC of about 16 000 yuan·person-1 and a unit area GEPC of about 0.04 billion yuan·km-2, which is a big gap with Anji County in eastern Zhejiang Province. This study is a typical case of accounting for the value of climate eco-products under the model of “climate factor-service function-economic value” developed under the framework of GEP, which can provide an important reference for accounting for the value of climate eco-products in other regions of the country, and also provide important decision support for the development of climate investment and financing, and the development of industries related to climate eco-products. It can also provide important decision-making support in the fields of climate investment and financing, and the development of industries related to climate ecological products.
Accounting for the value of climate ecological products based on climate resources is an important branch of the accounting system of gross ecosystem product (GEP), which is of great scientific value in solving the bottleneck of the system of "difficult to measure and difficult to mortgage" of climate resources. It is of key scientific significance in promoting the asset-based management of climate resources and realizing the value of ecological products. In this study, Fengjie County in Chongqing Municipality, is used as a case study to explore the construction of a gross climate ecosystem product (GEPC) accounting system from the perspective of the contribution of climate to ecological products. Utilizing meteorological, ecological environment and socio-economic data, we established an accounting framework of 12 specific indexes containing the three major functions of climate supply products, climate regulation services, and climate cultural services, and systematically assessed the value of climate ecosystem products in Fengjie County, Chongqing Municipality, from 2019 to 2023. The results show that the annual mean value of GEPC in Fengjie County in 2019–2023 is 17.17 billion yuan, accounting for 48% of GDP; the structural characteristics are dominated by "climate regulation" (57.0% of the value of climate regulation services > 38.5% of the value of climate supply products >4.4% of the value of climate cultural services). The GEPC fluctuates from 13.92 billion yuan to 20.95 billion yuan between years, with the peak year (2023) being 1.5 times the lowest years (2019). The ratio of GEPC to GDP in Fengjie County ranges from 0.36 to 0.56 (mean value 0.48) in 2019–2023, with reference to the Green Gold Index, which reflects to some extent the dynamic coupling of the transformation of the value of climatic resources and the level of economic development. Fengjie County has a per capita GEPC of about 16 000 yuan·person-1 and a unit area GEPC of about 0.04 billion yuan·km-2, which is a big gap with Anji County in eastern Zhejiang Province. This study is a typical case of accounting for the value of climate eco-products under the model of “climate factor-service function-economic value” developed under the framework of GEP, which can provide an important reference for accounting for the value of climate eco-products in other regions of the country, and also provide important decision support for the development of climate investment and financing, and the development of industries related to climate eco-products. It can also provide important decision-making support in the fields of climate investment and financing, and the development of industries related to climate ecological products.
Available online: September 02, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.080601
Abstract:
Based on the S-band dual-polarization radar data from Qingpu (Shanghai), Nantong (Jiangsu), Hangzhou, Jiaxing and Huzhou (Zhejiang), the effectiveness evaluation of three volume scan patterns (VCP21D, VCP11D, and VCP216D) are assessed under general precipitation, severe convective and typhoon conditions. The evaluation is based on three methods: subjective identification of characteristic tracer factors, interpolation of reflectivity factor isosurfaces, and wind field retrieve using dual-radar data. The results indicate that both VCP21D and VCP11D can accurately identify the zero-degree bright band characteristic. VCP21D, compared to VCP11D, shows better stability in recognizing the melting layer height, with a smaller standard deviation and a better match to actual conditions. The convective scan patterns (VCP11D and VCP216D) significantly enhance vertical observational resolution compared to the precipitation mode (VCP21D). This improvement is crucial for detecting key severe weather phenomena, such as columns and mesoscale cyclones. Meanwhile, the additional 1.0° elevation angle in VCP216D volume scan pattern is particularly effective in capturing mesoscale features such as low-level gust fronts and sea breeze fronts. Also, this additional scan cut eliminates the effect from ground clutter echoes for data quality improvement. The data from VCP11D and VCP216D volume scan pattern shows great advantages in generating constant altitude plan position indicator (CAPPI), characterize the details special above 5 km altitude, compared to VCP21D volume scan pattern. in both isosurface interpolation and wind field inversion. In the comparison of wind field retrieve, the availability and accuracy of the retrieved data significantly improved, from double VCP11D volume scan pattern radar compared to VCP21D mode.
Based on the S-band dual-polarization radar data from Qingpu (Shanghai), Nantong (Jiangsu), Hangzhou, Jiaxing and Huzhou (Zhejiang), the effectiveness evaluation of three volume scan patterns (VCP21D, VCP11D, and VCP216D) are assessed under general precipitation, severe convective and typhoon conditions. The evaluation is based on three methods: subjective identification of characteristic tracer factors, interpolation of reflectivity factor isosurfaces, and wind field retrieve using dual-radar data. The results indicate that both VCP21D and VCP11D can accurately identify the zero-degree bright band characteristic. VCP21D, compared to VCP11D, shows better stability in recognizing the melting layer height, with a smaller standard deviation and a better match to actual conditions. The convective scan patterns (VCP11D and VCP216D) significantly enhance vertical observational resolution compared to the precipitation mode (VCP21D). This improvement is crucial for detecting key severe weather phenomena, such as columns and mesoscale cyclones. Meanwhile, the additional 1.0° elevation angle in VCP216D volume scan pattern is particularly effective in capturing mesoscale features such as low-level gust fronts and sea breeze fronts. Also, this additional scan cut eliminates the effect from ground clutter echoes for data quality improvement. The data from VCP11D and VCP216D volume scan pattern shows great advantages in generating constant altitude plan position indicator (CAPPI), characterize the details special above 5 km altitude, compared to VCP21D volume scan pattern. in both isosurface interpolation and wind field inversion. In the comparison of wind field retrieve, the availability and accuracy of the retrieved data significantly improved, from double VCP11D volume scan pattern radar compared to VCP21D mode.
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 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.
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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.
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.
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.
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.
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).
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(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.
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.
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