ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 50,2024 Issue 11
indexed by
- Recommended Topics
-
- 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
- Current Issue
- Online First
- Archive
- Most Downloaded
Select AllDeselectExport
Display Method:
2024,50(11):1289-1305, DOI: 10.7519/j.issn.1000-0526.2024.081901
Abstract:
This study utilized ERA5 reanalysis data and multiple observations to investigate the weakening and strengthening of the remnant vortex of Typhoon Doksuri (2023) in the Northwest Pacific after its landfall. It caused significant damages in northern China. The main maintenance and recovery period were observed from the night of July 29th to the daytime of July 30th. The study result reveals that during the maintenance of the remnant vortex, it had a warm-core structure and was not influenced by dry and cold air. During the recovery process, a noticeable increase in water vapor convergence and moist potential vorticity were observed on the northeastern side of the remnant vortex center. Additionally, the northward movement of the remnant vortex was hindered by a zonal subtropical high belt, causing a reduction in its northward-moving speed. Under the guidance of a mid- and high-level high-pressure system, the dry and cold air further intensified the temperature and moisture gradients between the mid- and low-level remnant vortex and warm-moist air masses, resulting in a clear tilt of isentropic surfaces on the northern side of the vortex. This tilt in isentropic surfaces led to the vertical development of cyclonic vortex. Furthermore, during the maintenance and recovery period, the remnant vortex continued to receive some heating from the increased soil moisture. Additionally, significant condensation latent heat was released due to radial moisture inflow and vertical upward motion on the northeastern side of the remnant vortex. This release of latent heat provided necessary conditions for the maintenance and strengthening of the remnant vortex.
This study utilized ERA5 reanalysis data and multiple observations to investigate the weakening and strengthening of the remnant vortex of Typhoon Doksuri (2023) in the Northwest Pacific after its landfall. It caused significant damages in northern China. The main maintenance and recovery period were observed from the night of July 29th to the daytime of July 30th. The study result reveals that during the maintenance of the remnant vortex, it had a warm-core structure and was not influenced by dry and cold air. During the recovery process, a noticeable increase in water vapor convergence and moist potential vorticity were observed on the northeastern side of the remnant vortex center. Additionally, the northward movement of the remnant vortex was hindered by a zonal subtropical high belt, causing a reduction in its northward-moving speed. Under the guidance of a mid- and high-level high-pressure system, the dry and cold air further intensified the temperature and moisture gradients between the mid- and low-level remnant vortex and warm-moist air masses, resulting in a clear tilt of isentropic surfaces on the northern side of the vortex. This tilt in isentropic surfaces led to the vertical development of cyclonic vortex. Furthermore, during the maintenance and recovery period, the remnant vortex continued to receive some heating from the increased soil moisture. Additionally, significant condensation latent heat was released due to radial moisture inflow and vertical upward motion on the northeastern side of the remnant vortex. This release of latent heat provided necessary conditions for the maintenance and strengthening of the remnant vortex.
2024,50(11):1306-1316, DOI: 10.7519/j.issn.1000-0526.2024.101201
Abstract:
The landfall tropical cyclones can often bring heavy precipitation to Liaodong Peninsula when they move northward into the Bohai Sea. Using CMA Tropical Cyclone Yearbook, cloud top brightness temperature and ERA-Interim reanalysis data, we conduct dynamic synthesis and diagnostic analysis of seven typhoons that caused heavy precipitation over the Liaodong Peninsula during their northward moving. The major conclusions are as follows. The typhoons experienced extratropical transition when approaching westerly troughs and had hybrid structures with remarkable baroclinic instability. Meanwhile, the vertical wind shear was enhanced, the vertical structure of the typhoon vortex slanted with height, and mesoscale convection developed on their north sides. The locations of heavy precipitation mainly occurred in the left side along with the direction of vertical wind shears. The standing link of typhoon with a deep southwestern or southeastern jet was favorable for the development of sustained convective activities in the typhoon rain belts, and the typhoons decayed slowly due to abundant moisture supply. Basically, strong-rainfall typhoons moved northward near the entrance area of the westerly jet stream in front of the trough, characterized by strong divergence in the upper layers. The coupling dynamical structure of positive divergence zone and the positive vorticity at lower levels formed, which was favorable for genesis of heavy precipitation and long-time substation of typhoon circulation. The cold air in the middle and upper troposphere invaded into typhoons’ northwest sides and the frontal zone slanted towards northwest with height, increasing the convective instability in the low-level front zone. The coupling dynamic structure of positive vorticity region and the divergence center further uplifted the air on their northeast sides and southeast sides. Liaodong Peninsula was in the north side of the typhoons, possessing strong low-level convergence, vertical wind shear, and deep and persistent vertical motion, thus the precipitation intensity was high and the duration was long over the Liaodong Peninsula.
The landfall tropical cyclones can often bring heavy precipitation to Liaodong Peninsula when they move northward into the Bohai Sea. Using CMA Tropical Cyclone Yearbook, cloud top brightness temperature and ERA-Interim reanalysis data, we conduct dynamic synthesis and diagnostic analysis of seven typhoons that caused heavy precipitation over the Liaodong Peninsula during their northward moving. The major conclusions are as follows. The typhoons experienced extratropical transition when approaching westerly troughs and had hybrid structures with remarkable baroclinic instability. Meanwhile, the vertical wind shear was enhanced, the vertical structure of the typhoon vortex slanted with height, and mesoscale convection developed on their north sides. The locations of heavy precipitation mainly occurred in the left side along with the direction of vertical wind shears. The standing link of typhoon with a deep southwestern or southeastern jet was favorable for the development of sustained convective activities in the typhoon rain belts, and the typhoons decayed slowly due to abundant moisture supply. Basically, strong-rainfall typhoons moved northward near the entrance area of the westerly jet stream in front of the trough, characterized by strong divergence in the upper layers. The coupling dynamical structure of positive divergence zone and the positive vorticity at lower levels formed, which was favorable for genesis of heavy precipitation and long-time substation of typhoon circulation. The cold air in the middle and upper troposphere invaded into typhoons’ northwest sides and the frontal zone slanted towards northwest with height, increasing the convective instability in the low-level front zone. The coupling dynamic structure of positive vorticity region and the divergence center further uplifted the air on their northeast sides and southeast sides. Liaodong Peninsula was in the north side of the typhoons, possessing strong low-level convergence, vertical wind shear, and deep and persistent vertical motion, thus the precipitation intensity was high and the duration was long over the Liaodong Peninsula.
2024,50(11):1317-1330, DOI: 10.7519/j.issn.1000-0526.2024.061801
Abstract:
To study the causes for rapid weakening and dissipation of Typhoon Bavi (No.2008) after its landfall in the north, in this study a numerical simulation is carried out with the non-hydrostatic mesoscale model WRF, and the simulated results are verified by the observation data. Furthermore, based on the high-resolution simulation results, the changes of the weather circulation background, ambient field and structural characteristics of Typhoon Bavi before and after its landfall are analyzed. The results indicate that “Bavi” was guided by the southwest airflow ahead of the mid-latitude westerly trough, and was located on the right side of the upper-level jet entrance area before its landfall. The divergence field at the upper level was conducive to maintaining the typhoon circulation. However, after its landfall, the intrusion of dry and cold air into the center of typhoon and the strong vertical wind shear were the main reasons for its loss in structure features and rapid weakening. After its landfall, the upper-level jet on the north side of typhoon decreased and the upper-level divergence weakened. Under such unfavorable upper-level circulation conditions, on the one hand, the strong vertical wind shear, especially from middle to high levels, increased the dispersion of warm air from the high-level warm core, which made the heat unable to concentrate and destroyed the upper warm core structure. On the other hand, the sinking cold air invaded the center of typhoon from the low level on the northwest side, and the vertical structure of “Bavi” was destroyed, then the height of warm core decreased and tilted to the northeast, so “Bavi” dissipated rapidly after its gradual loss of structure features. At the same time, insufficient water vapor supply after the landfall of “Bavi” was not good for its maintenance.
To study the causes for rapid weakening and dissipation of Typhoon Bavi (No.2008) after its landfall in the north, in this study a numerical simulation is carried out with the non-hydrostatic mesoscale model WRF, and the simulated results are verified by the observation data. Furthermore, based on the high-resolution simulation results, the changes of the weather circulation background, ambient field and structural characteristics of Typhoon Bavi before and after its landfall are analyzed. The results indicate that “Bavi” was guided by the southwest airflow ahead of the mid-latitude westerly trough, and was located on the right side of the upper-level jet entrance area before its landfall. The divergence field at the upper level was conducive to maintaining the typhoon circulation. However, after its landfall, the intrusion of dry and cold air into the center of typhoon and the strong vertical wind shear were the main reasons for its loss in structure features and rapid weakening. After its landfall, the upper-level jet on the north side of typhoon decreased and the upper-level divergence weakened. Under such unfavorable upper-level circulation conditions, on the one hand, the strong vertical wind shear, especially from middle to high levels, increased the dispersion of warm air from the high-level warm core, which made the heat unable to concentrate and destroyed the upper warm core structure. On the other hand, the sinking cold air invaded the center of typhoon from the low level on the northwest side, and the vertical structure of “Bavi” was destroyed, then the height of warm core decreased and tilted to the northeast, so “Bavi” dissipated rapidly after its gradual loss of structure features. At the same time, insufficient water vapor supply after the landfall of “Bavi” was not good for its maintenance.
2024,50(11):1331-1342, DOI: 10.7519/j.issn.1000-0526.2024.082101
Abstract:
Typhoon Haikui (2311) moved west-northwestward and repeatedly wobbled, forming a serpentine path. It strengthened into a super typhoon category before landing on Taiwan Island. Then, it moved slowly after entering the Taiwan Strait. After it landed again, its residual vortex sustained for about 5 days, resulting in the long-time precipitation and large accumulated rainfall. Different models and different members of ensemble forecast also had large errors and uncertainties in forecasting the landing spots and landfall strength of Haikui, which brought great challenges to forecast correction. ECMWF, NCEP and CMA deterministic forecast and ensemble forecast data are used to analyze the main characteristics of Haikui and critical difficulties in the process of operational forecast. There exist large errors and differences in the forecast of typhoon track in the offshore waters of China, and the operational correction problems in the intensity forecast are affected by the uncertainty of the track forecast. Besides, it is difficult to quantitatively estimate the time of the typhoon’s slowly moving that was caused by weak steering flow and terrain influence after the typhoon crossed Taiwan Island and entered the Taiwan Strait. Moreover, it is also difficult to quantitatively estimate the time of typhoon’s residual circulation maintenance, track and precipitation influence after the typhoon made landfall weakening.
Typhoon Haikui (2311) moved west-northwestward and repeatedly wobbled, forming a serpentine path. It strengthened into a super typhoon category before landing on Taiwan Island. Then, it moved slowly after entering the Taiwan Strait. After it landed again, its residual vortex sustained for about 5 days, resulting in the long-time precipitation and large accumulated rainfall. Different models and different members of ensemble forecast also had large errors and uncertainties in forecasting the landing spots and landfall strength of Haikui, which brought great challenges to forecast correction. ECMWF, NCEP and CMA deterministic forecast and ensemble forecast data are used to analyze the main characteristics of Haikui and critical difficulties in the process of operational forecast. There exist large errors and differences in the forecast of typhoon track in the offshore waters of China, and the operational correction problems in the intensity forecast are affected by the uncertainty of the track forecast. Besides, it is difficult to quantitatively estimate the time of the typhoon’s slowly moving that was caused by weak steering flow and terrain influence after the typhoon crossed Taiwan Island and entered the Taiwan Strait. Moreover, it is also difficult to quantitatively estimate the time of typhoon’s residual circulation maintenance, track and precipitation influence after the typhoon made landfall weakening.
2024,50(11):1343-1358, DOI: 10.7519/j.issn.1000-0526.2024.081902
Abstract:
Improving the accuracy of objective classification and spatio-temporal forecast of severe convective weather has always been a challenge in meteorological forecasting. This paper integrates mesoscale models with machine learning classification algorithms, achieving hourly forecasting of classified severe convection. The specific algorithm is as follows. First, the XGBoost classification algorithm and historical data over 10 years are used to establish a classification potential forecast model for severe convection. Secondly, by statistically analyzing the optimal spatial neighborhood radius and probability density distribution characteristics of CMA-SH9 model elements, and extracting element thresholds based on the combination of optimal scores, a spatial neighborhood graded element ingredient model is established. Finally, through joint discrimination, the machine learning classification method and the spatial neighborhood element “ingredient method” are integrated to establish hourly forecast models for thunderstorm gales and short-time heavy rainfall. The validation results show that this fusion algorithm significantly outperforms numerical model forecast results and national guidance products. For short-time heavy rainfall forecasts on an hourly basis over 24 h during 2021-2022, the average hit rate is 0.51 and the TS (threat score) is 0.15, which reflects the improvements of 82% and 36% respectively compared to the model. For thunderstorm gale forecasts on an hourly basis over 24 h, the average hit rate reaches 0.37 and the TS is 0.07, representing improvements of 68% and 133% respectively relative to the model (reflectivity factor ≥45 dBz). Thus, the forecast accuracy of thunderstorm gale is significantly improved.
Improving the accuracy of objective classification and spatio-temporal forecast of severe convective weather has always been a challenge in meteorological forecasting. This paper integrates mesoscale models with machine learning classification algorithms, achieving hourly forecasting of classified severe convection. The specific algorithm is as follows. First, the XGBoost classification algorithm and historical data over 10 years are used to establish a classification potential forecast model for severe convection. Secondly, by statistically analyzing the optimal spatial neighborhood radius and probability density distribution characteristics of CMA-SH9 model elements, and extracting element thresholds based on the combination of optimal scores, a spatial neighborhood graded element ingredient model is established. Finally, through joint discrimination, the machine learning classification method and the spatial neighborhood element “ingredient method” are integrated to establish hourly forecast models for thunderstorm gales and short-time heavy rainfall. The validation results show that this fusion algorithm significantly outperforms numerical model forecast results and national guidance products. For short-time heavy rainfall forecasts on an hourly basis over 24 h during 2021-2022, the average hit rate is 0.51 and the TS (threat score) is 0.15, which reflects the improvements of 82% and 36% respectively compared to the model. For thunderstorm gale forecasts on an hourly basis over 24 h, the average hit rate reaches 0.37 and the TS is 0.07, representing improvements of 68% and 133% respectively relative to the model (reflectivity factor ≥45 dBz). Thus, the forecast accuracy of thunderstorm gale is significantly improved.
2024,50(11):1359-1372, DOI: 10.7519/j.issn.1000-0526.2024.022102
Abstract:
A total of 184 hail weather cases in Chengde Mountains from April to September in 2000-2020 are analyzed by means of multi-source data including the hail observation, CINRAD/CB weather radar data, NCEP FNL reanalysis data, and NCEP-GFS forecasts. Firstly, the distribution characteristics and forecast thresholds of relevant ambient parameters such as water vapor, thermal instability, dynamic lift and characteristic height are analyzed in the form of box plots. Then, the initial optimal threshold values are set according to the results of box plots. The hail labels are determined according to the hail observation records or composite reflectivity greater than or equal to 60 dBz from April to September in 2014-2020. The hail labels are matched to the grids of reanalysis data according to the principle of near location and proximity time to construct the positive and negative sample dataset for feature parameter selection, interval segmentation and probability calculation. Next, five models for 3, 6, 9, 12 and 24 h hail potential forecast are established by the Bayesian method. The models are tested focusing on the weather processess from June to August during 2021-2022. The results suggest that the Bayesian-based hail potential prediction models have a certain feasibility in daily weather forecasting. The hit rates of all the models are above 90%, and the average critical success index is over 40.3%. Differing from the traditional probability and ingredient methods, the method can provide a better objective forecast of hail occurrence, which has a certain reference value for forecasting severe convective weather in mountainous areas. However, there are some false alarms as the spatio-temporal scale of the reanalysis data is much larger than that of severe convective weather, which needs to be improved in the future.
A total of 184 hail weather cases in Chengde Mountains from April to September in 2000-2020 are analyzed by means of multi-source data including the hail observation, CINRAD/CB weather radar data, NCEP FNL reanalysis data, and NCEP-GFS forecasts. Firstly, the distribution characteristics and forecast thresholds of relevant ambient parameters such as water vapor, thermal instability, dynamic lift and characteristic height are analyzed in the form of box plots. Then, the initial optimal threshold values are set according to the results of box plots. The hail labels are determined according to the hail observation records or composite reflectivity greater than or equal to 60 dBz from April to September in 2014-2020. The hail labels are matched to the grids of reanalysis data according to the principle of near location and proximity time to construct the positive and negative sample dataset for feature parameter selection, interval segmentation and probability calculation. Next, five models for 3, 6, 9, 12 and 24 h hail potential forecast are established by the Bayesian method. The models are tested focusing on the weather processess from June to August during 2021-2022. The results suggest that the Bayesian-based hail potential prediction models have a certain feasibility in daily weather forecasting. The hit rates of all the models are above 90%, and the average critical success index is over 40.3%. Differing from the traditional probability and ingredient methods, the method can provide a better objective forecast of hail occurrence, which has a certain reference value for forecasting severe convective weather in mountainous areas. However, there are some false alarms as the spatio-temporal scale of the reanalysis data is much larger than that of severe convective weather, which needs to be improved in the future.
2024,50(11):1373-1385, DOI: 10.7519/j.issn.1000-0526.2024.063002
Abstract:
The round-trip drifting sounding system (RDSS) can detect the atmospheric temperature profile vertically from ground to the lower stratosphere and the horizontal temperature distribution in the lower stratosphere continuously for 4 hours. Round-trip drifting sounding observation tests have been carried out in the middle and lower reaches of the Yangtze River, Guangdong, Inner Mongolia and other places, and the results are very successful. Based on the data of round-trip drifting sounding tests in the middle and lower reaches of the Yangtze River from March to September 2021, this paper conducts the verification of atmospheric humidity profile data of satellite. The verification results of the descending phase data of the round-trip drifting sounding indicate that the average absolute error of the satellite humidity profile is about 15%, and the root mean square error is approximately 20%. At noon and night, the quality of humidity profile data of satellite is better than that in the morning and evening. The humidity average absolute error of the satellite decreases with increasing altitude and increases with increasing humidity. Below the 50% humidity, the satellite-retrieved humidity is relatively large, but for the humidity above 50%, the satellite-retrieved humidity is relatively small.
The round-trip drifting sounding system (RDSS) can detect the atmospheric temperature profile vertically from ground to the lower stratosphere and the horizontal temperature distribution in the lower stratosphere continuously for 4 hours. Round-trip drifting sounding observation tests have been carried out in the middle and lower reaches of the Yangtze River, Guangdong, Inner Mongolia and other places, and the results are very successful. Based on the data of round-trip drifting sounding tests in the middle and lower reaches of the Yangtze River from March to September 2021, this paper conducts the verification of atmospheric humidity profile data of satellite. The verification results of the descending phase data of the round-trip drifting sounding indicate that the average absolute error of the satellite humidity profile is about 15%, and the root mean square error is approximately 20%. At noon and night, the quality of humidity profile data of satellite is better than that in the morning and evening. The humidity average absolute error of the satellite decreases with increasing altitude and increases with increasing humidity. Below the 50% humidity, the satellite-retrieved humidity is relatively large, but for the humidity above 50%, the satellite-retrieved humidity is relatively small.
2024,50(11):1386-1396, DOI: 10.7519/j.issn.1000-0526.2024.070301
Abstract:
Wind observation data are very important in weather research and forecasting. The IVAP technique, which is based on the azimuth uniform assumption retrieval relationship, offers good compatibility and practical simplicity for 2-D wind field retrieval. In this paper, the large-scale precipitation events from July to August 2020 are selected, and the wind fields from the Doppler radar network are retrieved by the IVAP method. At the same time, the quality of the retrieved wind fields is evaluated and analyzed with the seconds-sounding data as a reference. The results indicate that the retrieved wind fields of Doppler radar network have a high correlation with the sounding data, and the quality of wind direction data is better than the wind speed data with altitude rising. The quality of the retrieved winds is better in precipitation areas than in the non-precipitation areas. Moreover, the quality of wind field and the stability of vertical profile are the best in precipitation areas, but the quality of the retrieved winds is the worst in clear sky areas, especially when the altitude is higher than 4 km. The retrieved winds of a scattered precipitation process on 6 July 2019 are further analyzed, which demonstrates that the retrieved wind field can reasonably reproduce the dynamic field characteristics such as vortex structure and shear line of the upper wind field. This study shows that based on the single Doppler radar wind field retrieval, the IVAP method has the ability to retrieve wind fields of Doppler radar network, so the method will have a good application prospect in practical operations, and can provide a better basis for weather forecasting services and wind data assimilation.
Wind observation data are very important in weather research and forecasting. The IVAP technique, which is based on the azimuth uniform assumption retrieval relationship, offers good compatibility and practical simplicity for 2-D wind field retrieval. In this paper, the large-scale precipitation events from July to August 2020 are selected, and the wind fields from the Doppler radar network are retrieved by the IVAP method. At the same time, the quality of the retrieved wind fields is evaluated and analyzed with the seconds-sounding data as a reference. The results indicate that the retrieved wind fields of Doppler radar network have a high correlation with the sounding data, and the quality of wind direction data is better than the wind speed data with altitude rising. The quality of the retrieved winds is better in precipitation areas than in the non-precipitation areas. Moreover, the quality of wind field and the stability of vertical profile are the best in precipitation areas, but the quality of the retrieved winds is the worst in clear sky areas, especially when the altitude is higher than 4 km. The retrieved winds of a scattered precipitation process on 6 July 2019 are further analyzed, which demonstrates that the retrieved wind field can reasonably reproduce the dynamic field characteristics such as vortex structure and shear line of the upper wind field. This study shows that based on the single Doppler radar wind field retrieval, the IVAP method has the ability to retrieve wind fields of Doppler radar network, so the method will have a good application prospect in practical operations, and can provide a better basis for weather forecasting services and wind data assimilation.
2024,50(11):1397-1408, DOI: 10.7519/j.issn.1000-0526.2024.050601
Abstract:
Using the 3 h observation data from national-level stations in Beijing Region in spring (February to April) during 2019-2021, we evaluate the temperature forecasts made by numerical models including European Centre for Medium-Range Weather Forecasting (ECMWF) and Global and Regional Assimilation and Prediction System (CMA-GFS), and by national gridded guidance forecast product (SCMOC) as well as the revised feedback gridded forecast product at provincial level (SMERGE). The results show that the spring temperature forecasts in Beijing by the models of ECMWF and CMA-GFS often show negative biases. The biases have no significant difference in mountainous and plain areas, but more prominent during nighttime periods. The gridded forecast products (SCMOC and SMERGE) have a good ability to correct the temperature forecasted by the models (ECMWF and CMA-GFS). The temperature forecast biases of the gridded products are concentrated in the range of -1-1℃, meanwhile the forecast accuracy is higher and the mean absolute error is lower than that of model forecast. Some problems are found in the forecasts of 24 h temperature change and diurnal temperature range from the four products. The amplitude of intense 24 h temperature change forecasted by all products is relatively smaller than that of observation, and the gridded forecast products fail to demonstrate significant correction ability. In addition, the diurnal temperature range forecasted by all products has a positive deviation of 1-3℃ compared to the observation. SCMOC has a better correction ability for the diurnal temperature range by the models, while SMERGE overestimates the difference more prominently than that by models. The positive deviation of diurnal temperature range forecast is closely related to the underestimation of low temperature at 05:00 BT in the models, while the overestimation of high temperature at 14:00 BT can not be ignored in the grid forecasts. The refined analysis suggests that gridded forecast products should not only focus on improving overall accuracy (reducing biases), but also on the development and evolution of synoptic processes.
Using the 3 h observation data from national-level stations in Beijing Region in spring (February to April) during 2019-2021, we evaluate the temperature forecasts made by numerical models including European Centre for Medium-Range Weather Forecasting (ECMWF) and Global and Regional Assimilation and Prediction System (CMA-GFS), and by national gridded guidance forecast product (SCMOC) as well as the revised feedback gridded forecast product at provincial level (SMERGE). The results show that the spring temperature forecasts in Beijing by the models of ECMWF and CMA-GFS often show negative biases. The biases have no significant difference in mountainous and plain areas, but more prominent during nighttime periods. The gridded forecast products (SCMOC and SMERGE) have a good ability to correct the temperature forecasted by the models (ECMWF and CMA-GFS). The temperature forecast biases of the gridded products are concentrated in the range of -1-1℃, meanwhile the forecast accuracy is higher and the mean absolute error is lower than that of model forecast. Some problems are found in the forecasts of 24 h temperature change and diurnal temperature range from the four products. The amplitude of intense 24 h temperature change forecasted by all products is relatively smaller than that of observation, and the gridded forecast products fail to demonstrate significant correction ability. In addition, the diurnal temperature range forecasted by all products has a positive deviation of 1-3℃ compared to the observation. SCMOC has a better correction ability for the diurnal temperature range by the models, while SMERGE overestimates the difference more prominently than that by models. The positive deviation of diurnal temperature range forecast is closely related to the underestimation of low temperature at 05:00 BT in the models, while the overestimation of high temperature at 14:00 BT can not be ignored in the grid forecasts. The refined analysis suggests that gridded forecast products should not only focus on improving overall accuracy (reducing biases), but also on the development and evolution of synoptic processes.
2024,50(11):1409-1416, DOI: 10.7519/j.issn.1000-0526.2024.102301
Abstract:
The main characteristics of the general atmospheric circulation in August 2024 are as follows. There were two polar vortex centers in the Northern Hemisphere and they were stronger than normal. The circulation at middle-high latitude of the Eurasia showed a two-trough and two-ridge pattern. The location of the western Pacific subtropical high was more westward and northward compared to that in normal years. In August, the monthly average precipitation in China was 96.5 mm, 9.9% lower than normal (107.1 mm), and the monthly average temperature was 22.6℃, higher than normal (21.1℃) by 1.5℃. During this month, the high temperature days were more than normal for the same period of the year. The continuous high temperature weather in southern China was highly extreme, and meteorological drought developed along the middle and upper reaches of the Yangtze River. Five torrential rain processes occurred in China, and rainstorm events appeared frequently in northern China, with high overlap of rainstorm-hit areas and strong disaster causing ability. There were six tropical cyclones active over the Northwest Pacific in August, and no tropical cyclones formed or passed through the South China Sea or landed in China. Severe convection events occurred frequently and dispersedly, causing localized serious damages.
The main characteristics of the general atmospheric circulation in August 2024 are as follows. There were two polar vortex centers in the Northern Hemisphere and they were stronger than normal. The circulation at middle-high latitude of the Eurasia showed a two-trough and two-ridge pattern. The location of the western Pacific subtropical high was more westward and northward compared to that in normal years. In August, the monthly average precipitation in China was 96.5 mm, 9.9% lower than normal (107.1 mm), and the monthly average temperature was 22.6℃, higher than normal (21.1℃) by 1.5℃. During this month, the high temperature days were more than normal for the same period of the year. The continuous high temperature weather in southern China was highly extreme, and meteorological drought developed along the middle and upper reaches of the Yangtze River. Five torrential rain processes occurred in China, and rainstorm events appeared frequently in northern China, with high overlap of rainstorm-hit areas and strong disaster causing ability. There were six tropical cyclones active over the Northwest Pacific in August, and no tropical cyclones formed or passed through the South China Sea or landed in China. Severe convection events occurred frequently and dispersedly, causing localized serious damages.
Select AllDeselectExport
Display Method:
Available online: December 19, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.121201
Abstract:
Backward tracking and quantitative analysis of water vapor transport at different altitudes during rainstorms on the eastern, western, and east-west foot of Helan Mountains from 2001 to 2019 were conducted using the HYSPLIT trajectory model, based on hourly precipitation observations and GDAS reanalysis data with a spatial resolution of 1.0°×1.0° and a temporal resolution of 6 hours. It was found that significant differences exist in water vapor transport patterns at different altitudes during rainstorms across different regions of Helan Mountains. At the eastern foot, the southerly path was identified as the primary transport route below 3000 m, with a water vapor contribution rate of 57.3% to 75.2%. The contribution of the westerly path was observed to increase with altitude, reaching 100% at 5000 m. At the western foot, the westerly path was found to be the dominant transport route, with a water vapor contribution rate ranging from 31.8% to 67.5%. The southerly path was observed to be secondary, with contributions ranging from 23.8% to 68.2%, while the northerly path appeared only at 100 m and 1000 m, contributing 28.9% to 39.4%. In the east-west foot region, the westerly path was determined to contribute 100% of the water vapor at all altitudes. The Eurasian westerlies were identified as the predominant source of water vapor, particularly during rainstorms in the east-west foot region, where the water vapor contribution was the highest at all altitudes except at 1000 m. Secondary water vapor sources included the Qinghai and Gansu regions, the Middle-Lower Yangtze Plains, and the waters of the Black Sea, Caspian Sea, Lake Balkhash, and Lake Baikal, which were found to supply moisture to rainstorms at the east-west, eastern, and western feet, respectively. The Hengduan Mountains were identified as contributing moisture at isolated altitudes during rainstorms at the eastern and western feet, though its contribution was minimal.
Backward tracking and quantitative analysis of water vapor transport at different altitudes during rainstorms on the eastern, western, and east-west foot of Helan Mountains from 2001 to 2019 were conducted using the HYSPLIT trajectory model, based on hourly precipitation observations and GDAS reanalysis data with a spatial resolution of 1.0°×1.0° and a temporal resolution of 6 hours. It was found that significant differences exist in water vapor transport patterns at different altitudes during rainstorms across different regions of Helan Mountains. At the eastern foot, the southerly path was identified as the primary transport route below 3000 m, with a water vapor contribution rate of 57.3% to 75.2%. The contribution of the westerly path was observed to increase with altitude, reaching 100% at 5000 m. At the western foot, the westerly path was found to be the dominant transport route, with a water vapor contribution rate ranging from 31.8% to 67.5%. The southerly path was observed to be secondary, with contributions ranging from 23.8% to 68.2%, while the northerly path appeared only at 100 m and 1000 m, contributing 28.9% to 39.4%. In the east-west foot region, the westerly path was determined to contribute 100% of the water vapor at all altitudes. The Eurasian westerlies were identified as the predominant source of water vapor, particularly during rainstorms in the east-west foot region, where the water vapor contribution was the highest at all altitudes except at 1000 m. Secondary water vapor sources included the Qinghai and Gansu regions, the Middle-Lower Yangtze Plains, and the waters of the Black Sea, Caspian Sea, Lake Balkhash, and Lake Baikal, which were found to supply moisture to rainstorms at the east-west, eastern, and western feet, respectively. The Hengduan Mountains were identified as contributing moisture at isolated altitudes during rainstorms at the eastern and western feet, though its contribution was minimal.
Available online: December 17, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.111201
Abstract:
In order to improve the monitoring and early warning capabilities of autumn hail, this paper based on the dual-polarization radar and FY-4A satellite data, analyzed a rare autumn strong hail process that occurred in Hunan on 9 November 2023, discussed its early warning characteristics. The findings are as follows: (1) Strong hail is produced by supercell hailstorms,in the hail stage , the bottom of the strong echo center (horizontal reflectivity factor ZH ≥65 dBz) is close to the ground, correlation coefficient (CC)< 0.9, differential phase shift rate (KDP) is a cavity, and differential reflectivity factor (ZDR) is -3-0 dB, corresponding to the fall of large hail with a diameter ≥ 5 cm, which is consistent with the actual situation.The rise and fall of the ZDR column can characterize the Strengthening and weakening of updraft, ZDR combined with CC can identify three body scatter signature(TBSS) and side lobe characteristics. It is necessary to strengthen the comprehensive application of multiple dual-polarization parameters when monitoring and warning of strong convection.(2) The area of strong echo and the height of the center of mass are good indicators of the different development stages of supercell. Combined monitoring, the advance warning of hail can reach more than 12 minutes.The length of TBSS caused by the supercell in this process reached a rare 73 km. The emergence of TBSS and the divergence of the storm top showed a significant weakening trend, which was more than 17 minutes earlier than the hailstorm time.(3) Hail and thunderstorm winds appear in areas with large gradients of hail cloud blackbody brightness temperature (TBB), cloud top temperature (CTT), cloud top height (CTH), and cloud top pressure (CTP).TBB≤-58 ℃, CTT≤-56 ℃, CTH≥13 km,CTP≤180 hPa and the continuous increase of TBB≤-52 ℃ area can be used as monitoring and early warning of the characteristic parameters of autumn hail cloud by FY-4A satellite index.(4) The TBB maximum decrement rate can provide at least 11 minutes of advance warning for impending hail.The brightness temperature difference of 10.8-13.3 μm channel is the most sensitive to the development and weakening of hail clouds. The brightness temperature difference of 6.5-10.8 μm channel is more sensitive to before and after the hail passes through than other brightness temperature differences in single-station convection monitoring indicators.
In order to improve the monitoring and early warning capabilities of autumn hail, this paper based on the dual-polarization radar and FY-4A satellite data, analyzed a rare autumn strong hail process that occurred in Hunan on 9 November 2023, discussed its early warning characteristics. The findings are as follows: (1) Strong hail is produced by supercell hailstorms,in the hail stage , the bottom of the strong echo center (horizontal reflectivity factor ZH ≥65 dBz) is close to the ground, correlation coefficient (CC)< 0.9, differential phase shift rate (KDP) is a cavity, and differential reflectivity factor (ZDR) is -3-0 dB, corresponding to the fall of large hail with a diameter ≥ 5 cm, which is consistent with the actual situation.The rise and fall of the ZDR column can characterize the Strengthening and weakening of updraft, ZDR combined with CC can identify three body scatter signature(TBSS) and side lobe characteristics. It is necessary to strengthen the comprehensive application of multiple dual-polarization parameters when monitoring and warning of strong convection.(2) The area of strong echo and the height of the center of mass are good indicators of the different development stages of supercell. Combined monitoring, the advance warning of hail can reach more than 12 minutes.The length of TBSS caused by the supercell in this process reached a rare 73 km. The emergence of TBSS and the divergence of the storm top showed a significant weakening trend, which was more than 17 minutes earlier than the hailstorm time.(3) Hail and thunderstorm winds appear in areas with large gradients of hail cloud blackbody brightness temperature (TBB), cloud top temperature (CTT), cloud top height (CTH), and cloud top pressure (CTP).TBB≤-58 ℃, CTT≤-56 ℃, CTH≥13 km,CTP≤180 hPa and the continuous increase of TBB≤-52 ℃ area can be used as monitoring and early warning of the characteristic parameters of autumn hail cloud by FY-4A satellite index.(4) The TBB maximum decrement rate can provide at least 11 minutes of advance warning for impending hail.The brightness temperature difference of 10.8-13.3 μm channel is the most sensitive to the development and weakening of hail clouds. The brightness temperature difference of 6.5-10.8 μm channel is more sensitive to before and after the hail passes through than other brightness temperature differences in single-station convection monitoring indicators.
Available online: December 17, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.111802
Abstract:
This study used the high-resolution operational model CMA-MESO to simulate convective cloud precipitation in Shandong Province using a double-moment microphysical scheme with/without hail. Through comparative analysis, the mechanism of hail microphysical effects of convective cloud precipitation and the predictive ability of the operational model on hail forecasting were studied. The results showed that CMA-MESO simulated the convective precipitation process well. Compared with observations, the squall line life cycle in the model results was similar to the actual situation, and the distribution and magnitude of precipitation were close to the actual situation. The average liquid water and ice water path of the control group (including hail) in the simulated area is smaller than that of the experimental group (without hail). The rising speed of the convective core area in the control group slightly increases during convective development but decreases at other times. When hail occurs, the melting and heat absorption in the control group is stronger than in the experimental group. This might be due to the stronger falling speed of hail compared to other water condensates, which will suppress the development of convection during the falling process. In addition, increasing hail will affect convective precipitation. The proportion of moderate rain (1-10 mm) area to total precipitation area in the experimental group decreased, while the proportion of heavy rain and above (>10 mm) area to total precipitation area slightly increased. In terms of precipitation, with the increase of hail, there is no significant change in the intensity of medium to light precipitation, while the intensity of heavy rain precipitation increases.
This study used the high-resolution operational model CMA-MESO to simulate convective cloud precipitation in Shandong Province using a double-moment microphysical scheme with/without hail. Through comparative analysis, the mechanism of hail microphysical effects of convective cloud precipitation and the predictive ability of the operational model on hail forecasting were studied. The results showed that CMA-MESO simulated the convective precipitation process well. Compared with observations, the squall line life cycle in the model results was similar to the actual situation, and the distribution and magnitude of precipitation were close to the actual situation. The average liquid water and ice water path of the control group (including hail) in the simulated area is smaller than that of the experimental group (without hail). The rising speed of the convective core area in the control group slightly increases during convective development but decreases at other times. When hail occurs, the melting and heat absorption in the control group is stronger than in the experimental group. This might be due to the stronger falling speed of hail compared to other water condensates, which will suppress the development of convection during the falling process. In addition, increasing hail will affect convective precipitation. The proportion of moderate rain (1-10 mm) area to total precipitation area in the experimental group decreased, while the proportion of heavy rain and above (>10 mm) area to total precipitation area slightly increased. In terms of precipitation, with the increase of hail, there is no significant change in the intensity of medium to light precipitation, while the intensity of heavy rain precipitation increases.
Available online: December 12, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.113001
Abstract:
Abstract：In order to study the characteristics of downburst under weak vertical wind shear, based on SA Doppler weather radar, sounding and surface (10 m) maximum wind data and cloud image data of stationary meteorological satellites, 381 downburst events under weak vertical wind shear in Jiangsu from June to September in 2019 and 2020 were selected and divided into three categories according to the scale: microbursts, macrobursts, and downburst clusters. The statistical results show as follows: 64.9% of thunderstorm days in Jiangsu from June to September were accompanied by downburst, with an average of 8 downburst events per downburst day. The proportions of three types of downbursts are 21.7% for microbursts, 47.6% for macrobursts, and 30.7% for downburst clusters, which are concentrated at 15:00 to 16:00 (Beijing time). Based on radar radial velocity, the average duration of downbursts is 25.4 min, and the average intensity (radial velocity difference of divergence couplets or extreme radial velocity at low elevation) is 22 m·s-1. Only 7 times of downbursts reached the standard of disaster wind (extreme radial velocity at low elevation reached 25 m·s-1 or radial velocity difference of divergence couplets attained 40 m·s-1). The average surface maximum wind caused by downbursts observed by ground meteorological stations is 15.5 m·s-1, indicating that downbursts’ disaster-causing potential is not significant. The low elevation radial velocity modes of downbursts are dominated by divergence velocity couplets (73.3%), but the majority are asymmetric while only 6.1% of downbursts are symmetrical divergence velocity couplets. 26.7% of downbursts exhibit strong winds at low elevation.
Abstract：In order to study the characteristics of downburst under weak vertical wind shear, based on SA Doppler weather radar, sounding and surface (10 m) maximum wind data and cloud image data of stationary meteorological satellites, 381 downburst events under weak vertical wind shear in Jiangsu from June to September in 2019 and 2020 were selected and divided into three categories according to the scale: microbursts, macrobursts, and downburst clusters. The statistical results show as follows: 64.9% of thunderstorm days in Jiangsu from June to September were accompanied by downburst, with an average of 8 downburst events per downburst day. The proportions of three types of downbursts are 21.7% for microbursts, 47.6% for macrobursts, and 30.7% for downburst clusters, which are concentrated at 15:00 to 16:00 (Beijing time). Based on radar radial velocity, the average duration of downbursts is 25.4 min, and the average intensity (radial velocity difference of divergence couplets or extreme radial velocity at low elevation) is 22 m·s-1. Only 7 times of downbursts reached the standard of disaster wind (extreme radial velocity at low elevation reached 25 m·s-1 or radial velocity difference of divergence couplets attained 40 m·s-1). The average surface maximum wind caused by downbursts observed by ground meteorological stations is 15.5 m·s-1, indicating that downbursts’ disaster-causing potential is not significant. The low elevation radial velocity modes of downbursts are dominated by divergence velocity couplets (73.3%), but the majority are asymmetric while only 6.1% of downbursts are symmetrical divergence velocity couplets. 26.7% of downbursts exhibit strong winds at low elevation.
Available online: December 12, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.110501
Abstract:
Based on the X-band phased array radar data, this work studied the impact mechanisms of the fine characteristic on merger-formation bow echo and thunderstorm gusts which occurred under the background of Northeast China Cold Vortex. The results show that Liaoning was located in the southeast quadrant of the Northeast China Cold Vortex, and was influenced by low-level shear lines and low-level jet streams. The beneficial environment conditions such as extreme temperature differences between 850hPa and 500hPa were conducive to the occurrence of thunderstorm gust. However, the relative humidity near the ground at night was close to 70%, which was not conducive to the formation of strong cold pools. Therefore, there was no bow-shaped pattern in squall lines and the thunderstorm gusts were very scattered at this time. Subsequently, the squall line merged with the isolation storm. The shallow MVs generated at the merging height, and the rear-inflow jet (RIJ) had weakened. The micro downburst near MV created a strong cold pool near the ground. Under the joint stretching effect of the rising airflow at the edge of the cold pool and the original rising airflow of the storm, the MV was stretched and strengthened. Subsequently, the ZDR column formed over the MV, indicating the presence of strong updrafts and prolonging the duration of thunderstorms and strong winds in this area. Although the storm at the MV showed a bow-shaped pattern during this period, there were no thunderstorm gusts below the MV. When the updrafts weaken, there was a rapid decrease in the scale and concentration of precipitation particles within the storm. The evaporation of precipitation led to the formation of stronger and larger cold pools on the ground, and the development of RIJ below the MV. Although the MV with a bottom height higher than 2 km in this process could not cause strong winds directly, the thermodynamic and microphysical processes of the storm were affected by MV, leading to the concentration of thunderstorm winds in the strong cold pool and RIJ below the MV. Finally, the physical model of the thunderstorm winds caused by this MV is provided.Keywords: mesovortex, merger-formation bow echo, thunderstorm gusts, Northeast China Cold Vortex, phased array radar
Based on the X-band phased array radar data, this work studied the impact mechanisms of the fine characteristic on merger-formation bow echo and thunderstorm gusts which occurred under the background of Northeast China Cold Vortex. The results show that Liaoning was located in the southeast quadrant of the Northeast China Cold Vortex, and was influenced by low-level shear lines and low-level jet streams. The beneficial environment conditions such as extreme temperature differences between 850hPa and 500hPa were conducive to the occurrence of thunderstorm gust. However, the relative humidity near the ground at night was close to 70%, which was not conducive to the formation of strong cold pools. Therefore, there was no bow-shaped pattern in squall lines and the thunderstorm gusts were very scattered at this time. Subsequently, the squall line merged with the isolation storm. The shallow MVs generated at the merging height, and the rear-inflow jet (RIJ) had weakened. The micro downburst near MV created a strong cold pool near the ground. Under the joint stretching effect of the rising airflow at the edge of the cold pool and the original rising airflow of the storm, the MV was stretched and strengthened. Subsequently, the ZDR column formed over the MV, indicating the presence of strong updrafts and prolonging the duration of thunderstorms and strong winds in this area. Although the storm at the MV showed a bow-shaped pattern during this period, there were no thunderstorm gusts below the MV. When the updrafts weaken, there was a rapid decrease in the scale and concentration of precipitation particles within the storm. The evaporation of precipitation led to the formation of stronger and larger cold pools on the ground, and the development of RIJ below the MV. Although the MV with a bottom height higher than 2 km in this process could not cause strong winds directly, the thermodynamic and microphysical processes of the storm were affected by MV, leading to the concentration of thunderstorm winds in the strong cold pool and RIJ below the MV. Finally, the physical model of the thunderstorm winds caused by this MV is provided.Keywords: mesovortex, merger-formation bow echo, thunderstorm gusts, Northeast China Cold Vortex, phased array radar
Available online: December 05, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.100901
Abstract:
In order to solve the problem of traffic meteorological service in areas with a few observation stations, three regions in northern China (Beijing-Tianjin, Shaanxi-Gansu, Qinghai three typical regions) were selected. Traffic meteorological observational data, combined with the surface data from China Meteorological Administration Land Data Assimilation System (CLDAS), China Meteorological Administration Multisource Precipitation Analysis System (CMPAS), and surface short wave and long wave radiation retrieval products from FY-4A, were used to analyze the characteristics of road surface temperature and the relationship with the environmental meteorological factors in different regions, different seasons and different times. Three methods (linear regression, random forest, and deep neural network) were employed to construct a 1-hour updated road surface temperature real-time model. The model effectiveness was tested, and the effects of different methods, data combinations, and spatial generalization ability of the model were explored. Results show that: (1) The road surface temperature is significantly correlated with the environmental meteorological factors, but different regions, seasons, and time periods exhibit different detailed characteristics; (2) The independent test shows that there is no much difference among the model results based on different methods. They can all well reproduce the daily changes of road surface temperature at 14:00 (BJT) in summer and road surface temperature at 02:00 (BJT) in winter. The error in winter is significantly lower than that in summer. The application of satellite radiation products has a significant improvement effect on the road surface model results in summer. (3) The model has good spatial adaptability. However, compared with the model constructed by using local observations, the error of the model using data from nearby traffic stations in the same climate region shows increasing with different degrees, with the smallest increase in error in the Beijing-Tianjin region.
In order to solve the problem of traffic meteorological service in areas with a few observation stations, three regions in northern China (Beijing-Tianjin, Shaanxi-Gansu, Qinghai three typical regions) were selected. Traffic meteorological observational data, combined with the surface data from China Meteorological Administration Land Data Assimilation System (CLDAS), China Meteorological Administration Multisource Precipitation Analysis System (CMPAS), and surface short wave and long wave radiation retrieval products from FY-4A, were used to analyze the characteristics of road surface temperature and the relationship with the environmental meteorological factors in different regions, different seasons and different times. Three methods (linear regression, random forest, and deep neural network) were employed to construct a 1-hour updated road surface temperature real-time model. The model effectiveness was tested, and the effects of different methods, data combinations, and spatial generalization ability of the model were explored. Results show that: (1) The road surface temperature is significantly correlated with the environmental meteorological factors, but different regions, seasons, and time periods exhibit different detailed characteristics; (2) The independent test shows that there is no much difference among the model results based on different methods. They can all well reproduce the daily changes of road surface temperature at 14:00 (BJT) in summer and road surface temperature at 02:00 (BJT) in winter. The error in winter is significantly lower than that in summer. The application of satellite radiation products has a significant improvement effect on the road surface model results in summer. (3) The model has good spatial adaptability. However, compared with the model constructed by using local observations, the error of the model using data from nearby traffic stations in the same climate region shows increasing with different degrees, with the smallest increase in error in the Beijing-Tianjin region.
Available online: December 04, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.120201
Abstract:
Using the 3-hour densely-observed radiosonde and the 1-hour automatic weather station data obtained from Baolian, Chaoyang and Daxing station in Beijing from August 28, 2016 to September 2, 2016, based on the WRF model and the WRFDA three-dimensional variational assimilation system, this paper conducted assimilation experiments on only assimilating densely-observed radiosonde (S-DA), only assimilating automatic weather station data (A-DA), and simultaneously assimilating the above two types of data (M-DA), to study the improvement effect of three data assimilation schemes on the numerical simulation of the boundary layer in the Beijing area. The results show that: (1) In the vertical direction, densely-observed radiosonde plays a core role in improving simulation results, which can reduce the root mean square errors of temperature, humidity, and wind within the boundary layer range by 65%, 61%, and 22%, respectively. The automatic weather station data also contributes to the simulation results in the vertical direction, but the improvement is small and the impact range is low. The results of the M-DA test are similar to those of the S-DA test. (2) In the horizontal direction, the improvement effect of automatic weather station data is mainly reflected in a wide range of impact, with strong improvement efforts in densely-observed radiosonde, but the impact range is small. The advantages of combining two types of data in the M-DA experiment can make the simulation results closer to the observation results. (3) In terms of assimilation timeliness, the assimilation test has a relatively long effect on improving the thermal state within the boundary layer, and a relatively short effect on improving the humidity state and dynamic structure. Among them, the M-DA test can extend its effect on improving the thermal state up to 6 hours in the forecast, and its effect on improving the humidity and dynamic structure up to 3 hours in the forecast. In summary, the simultaneous assimilation of densely-observed radiosonde and automatic weather station data is more effective than assimilating either data alone. The two types of data can complement each other"s shortcomings after assimilation, which can greatly improve the initial field of the model and thus improve the accuracy of boundary layer simulation results to a certain extent.
Using the 3-hour densely-observed radiosonde and the 1-hour automatic weather station data obtained from Baolian, Chaoyang and Daxing station in Beijing from August 28, 2016 to September 2, 2016, based on the WRF model and the WRFDA three-dimensional variational assimilation system, this paper conducted assimilation experiments on only assimilating densely-observed radiosonde (S-DA), only assimilating automatic weather station data (A-DA), and simultaneously assimilating the above two types of data (M-DA), to study the improvement effect of three data assimilation schemes on the numerical simulation of the boundary layer in the Beijing area. The results show that: (1) In the vertical direction, densely-observed radiosonde plays a core role in improving simulation results, which can reduce the root mean square errors of temperature, humidity, and wind within the boundary layer range by 65%, 61%, and 22%, respectively. The automatic weather station data also contributes to the simulation results in the vertical direction, but the improvement is small and the impact range is low. The results of the M-DA test are similar to those of the S-DA test. (2) In the horizontal direction, the improvement effect of automatic weather station data is mainly reflected in a wide range of impact, with strong improvement efforts in densely-observed radiosonde, but the impact range is small. The advantages of combining two types of data in the M-DA experiment can make the simulation results closer to the observation results. (3) In terms of assimilation timeliness, the assimilation test has a relatively long effect on improving the thermal state within the boundary layer, and a relatively short effect on improving the humidity state and dynamic structure. Among them, the M-DA test can extend its effect on improving the thermal state up to 6 hours in the forecast, and its effect on improving the humidity and dynamic structure up to 3 hours in the forecast. In summary, the simultaneous assimilation of densely-observed radiosonde and automatic weather station data is more effective than assimilating either data alone. The two types of data can complement each other"s shortcomings after assimilation, which can greatly improve the initial field of the model and thus improve the accuracy of boundary layer simulation results to a certain extent.
Available online: December 03, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.080501
Abstract:
In the complex terrain of Sichuan region, although the frequency of thunderstorm gale is relatively low, the impact is significant, and there are few existing objective forecast products with low time resolution. In order to further improve the accuracy of thunderstorm gale forecasting under complex terrain in Sichuan, this article comprehensively considers terrain factors, model physical quantity factors, and time factors. According to the altitude, Sichuan is divided into high-altitude and low altitude areas. Based on three machine learning methods: random forest, adaptive boosting, and extreme random tree, a thunderstorm gale prediction model was constructed by using data from 2018 to 2021, makes a forecast for 2022 and obtains a 3-hour thunderstorm gale potential forecast, and then, using the climate background, the 3-hour forecast time is scaled down to 1-hour to form a 0-12 hour hourly thunderstorm gale forecast, and the forecasting effect is tested. The results showed that, the adaptive boosting method 3-hour thunderstorm gale forecast has the best effect, long term and individual case tests showed that the 0-12 hour thunderstorm gale forecast product obtained from adaptive boosting method is superior to National Meteorological Centre (NMC) forecast product, the TS score increased from 1.04 % to 5.95 %, and the false alarm rate decreased from 98.8 % to 80.8 %, indicating high business application value.
In the complex terrain of Sichuan region, although the frequency of thunderstorm gale is relatively low, the impact is significant, and there are few existing objective forecast products with low time resolution. In order to further improve the accuracy of thunderstorm gale forecasting under complex terrain in Sichuan, this article comprehensively considers terrain factors, model physical quantity factors, and time factors. According to the altitude, Sichuan is divided into high-altitude and low altitude areas. Based on three machine learning methods: random forest, adaptive boosting, and extreme random tree, a thunderstorm gale prediction model was constructed by using data from 2018 to 2021, makes a forecast for 2022 and obtains a 3-hour thunderstorm gale potential forecast, and then, using the climate background, the 3-hour forecast time is scaled down to 1-hour to form a 0-12 hour hourly thunderstorm gale forecast, and the forecasting effect is tested. The results showed that, the adaptive boosting method 3-hour thunderstorm gale forecast has the best effect, long term and individual case tests showed that the 0-12 hour thunderstorm gale forecast product obtained from adaptive boosting method is superior to National Meteorological Centre (NMC) forecast product, the TS score increased from 1.04 % to 5.95 %, and the false alarm rate decreased from 98.8 % to 80.8 %, indicating high business application value.
Formation of boundary layer convergence lines in the Hetao area and its convection triggering effect
Available online: November 27, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.100801
Abstract:
Based on encrypted ball sound data, encrypted surface weather station data, ERA5 (0.25 °×0.25 °) and the Linhe New Generation Weather Radar data, A detailed analysis was conducted on the boundary layer convergence lines(BLCL )formed by the surface differences between the Hetao irrigation area and the Kubuqi Desert in the Hetao region of the Yellow River in July and August 2022 and its role in convection triggering. The results indicated that the BLCL in the Hetao area was formed by the combined influence of surface differences, boundary layer atmospheric circulation and complex terrain. And the BLCL mainly occurred at the border between the Hetao irrigation area and the Kubuqi Desert, and in a smaller arid area along the southeast bank of the Yellow River, with BLCL lengths ranging from 100 to 200 km. BLCL was a shallow system with convection heights of approximately 1000 to 1300 m. The daily variation of BLCL was significant, with a high incidence period from 12:00 to 17:00, accounting for 80%. The probability of BLCL formation in July and August of midsummer was as high as 60%, and 39% of BLCL could trigger convection. The prediction indicators about the formation of BLCL were as follows: (1) The temperature in Hangjinhouqi (53420) in Hetao Irrigation District is 2.5 ℃ lower than that in Habailaigeng (C3183) in Kubuqi Desert,and the relative humidity difference between them is up to 20% .(2) Continuous strong southerly winds was in the Kubuqi Desert and Mu Us Sandy Land areas in Hetao area, with a maximum wind speed of 10 meters above the ground greater than 4 ms ? 1.(3) The sea level pressure field is high in the east and low in the west, and a dense isobaric zone was in the Jiziwan of Yellow River with 3-4 isobars. The formation of BLCL is of great significance to the convection triggering in this region, which is manifested in convection triggering, convection strengthening, and convection organization. Under different environmental conditions and weather system superposition configurations, the BLCL could trigger local convection, organized strong convection, torrentialSrain in Hetao area. The generation and convective triggering of BLCL in this specific region are closely related to the distribution characteristics of rapid increase in precipitation from west to east in the Hetao region.
Based on encrypted ball sound data, encrypted surface weather station data, ERA5 (0.25 °×0.25 °) and the Linhe New Generation Weather Radar data, A detailed analysis was conducted on the boundary layer convergence lines(BLCL )formed by the surface differences between the Hetao irrigation area and the Kubuqi Desert in the Hetao region of the Yellow River in July and August 2022 and its role in convection triggering. The results indicated that the BLCL in the Hetao area was formed by the combined influence of surface differences, boundary layer atmospheric circulation and complex terrain. And the BLCL mainly occurred at the border between the Hetao irrigation area and the Kubuqi Desert, and in a smaller arid area along the southeast bank of the Yellow River, with BLCL lengths ranging from 100 to 200 km. BLCL was a shallow system with convection heights of approximately 1000 to 1300 m. The daily variation of BLCL was significant, with a high incidence period from 12:00 to 17:00, accounting for 80%. The probability of BLCL formation in July and August of midsummer was as high as 60%, and 39% of BLCL could trigger convection. The prediction indicators about the formation of BLCL were as follows: (1) The temperature in Hangjinhouqi (53420) in Hetao Irrigation District is 2.5 ℃ lower than that in Habailaigeng (C3183) in Kubuqi Desert,and the relative humidity difference between them is up to 20% .(2) Continuous strong southerly winds was in the Kubuqi Desert and Mu Us Sandy Land areas in Hetao area, with a maximum wind speed of 10 meters above the ground greater than 4 ms ? 1.(3) The sea level pressure field is high in the east and low in the west, and a dense isobaric zone was in the Jiziwan of Yellow River with 3-4 isobars. The formation of BLCL is of great significance to the convection triggering in this region, which is manifested in convection triggering, convection strengthening, and convection organization. Under different environmental conditions and weather system superposition configurations, the BLCL could trigger local convection, organized strong convection, torrentialSrain in Hetao area. The generation and convective triggering of BLCL in this specific region are closely related to the distribution characteristics of rapid increase in precipitation from west to east in the Hetao region.
Available online: October 28, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.093001
Abstract:
The standard precipitation verificaiton method and the MODE spatial method were applied to evaluate the perfotmance of the CMA-MESO and CMA-SH9 models in predicting precipitation in the eastern region of China in 2021 in this article. The results show that two models have relatively high prediction skills for the second and third quarters, while the predition skills for the first and fourth quarters are relatively low. The regional numetical models have good application potential in warm season precipitation forecasting. Based on the TS and BIAS of the four quarters, the overall precipitation prediction skills of the CMA-MESO model in the third quarter are higher than those of the CMA-SH9 model, while in other seaons, the CMA-SH9 model has relatively higher prediction skills. Both models show a higher BIAS and a higher FAR in each quarter. Improving the shortcomings of these two aspects is an important way to enhance the precipitaiton prediction skills of regional models. The MODE verification results of the ’21.7’ rainstorm in Henan and typhoon ‘Fireworks’ show that CMA-MESO and CMA-SH9 models both have the characteristics of a large range of influence on the prediction of heavy rainfall above heavy rainstorm. CMA-MESO model is slightly better than CMA-SH9 model in forecasting the spatial pattern and influence range of heavy rainstorm precipitation objects.
The standard precipitation verificaiton method and the MODE spatial method were applied to evaluate the perfotmance of the CMA-MESO and CMA-SH9 models in predicting precipitation in the eastern region of China in 2021 in this article. The results show that two models have relatively high prediction skills for the second and third quarters, while the predition skills for the first and fourth quarters are relatively low. The regional numetical models have good application potential in warm season precipitation forecasting. Based on the TS and BIAS of the four quarters, the overall precipitation prediction skills of the CMA-MESO model in the third quarter are higher than those of the CMA-SH9 model, while in other seaons, the CMA-SH9 model has relatively higher prediction skills. Both models show a higher BIAS and a higher FAR in each quarter. Improving the shortcomings of these two aspects is an important way to enhance the precipitaiton prediction skills of regional models. The MODE verification results of the ’21.7’ rainstorm in Henan and typhoon ‘Fireworks’ show that CMA-MESO and CMA-SH9 models both have the characteristics of a large range of influence on the prediction of heavy rainfall above heavy rainstorm. CMA-MESO model is slightly better than CMA-SH9 model in forecasting the spatial pattern and influence range of heavy rainstorm precipitation objects.
Available online: October 28, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.102601
Abstract:
The atmospheric attenuation characteristics of the FY-3 precipitation measurement radar external calibration test site were analyzed using sounding data from the National High Altitude Meteorological Observatory in Xilinhot (Station No. 54102) throughout 2023. A rapid method for estimating atmospheric attenuation has been established by exploring the relationship between total precipitation water and attenuation. The results indicate that the annual variation of oxygen attenuation is very small, while water vapor attenuation has obvious seasonal characteristics. In addition, the attenuation of water vapor is closely related to the total amount of water vapor. The attenuation of water vapor in Ku band is numerically equivalent to approximately 1/250 of the total amount of water vapor, and the attenuation of water vapor in Ka band is approximately 4 times that of the Ku band. Moreover, there is good consistency between the attenuation estimated by the quick method and the attenuation calculated by the normal method, indicating that the quick method is reasonable and feasible. The calculation and analysis of atmospheric attenuation can lay the foundation for the smooth implementation of precipitation radar external calibration experiments.
The atmospheric attenuation characteristics of the FY-3 precipitation measurement radar external calibration test site were analyzed using sounding data from the National High Altitude Meteorological Observatory in Xilinhot (Station No. 54102) throughout 2023. A rapid method for estimating atmospheric attenuation has been established by exploring the relationship between total precipitation water and attenuation. The results indicate that the annual variation of oxygen attenuation is very small, while water vapor attenuation has obvious seasonal characteristics. In addition, the attenuation of water vapor is closely related to the total amount of water vapor. The attenuation of water vapor in Ku band is numerically equivalent to approximately 1/250 of the total amount of water vapor, and the attenuation of water vapor in Ka band is approximately 4 times that of the Ku band. Moreover, there is good consistency between the attenuation estimated by the quick method and the attenuation calculated by the normal method, indicating that the quick method is reasonable and feasible. The calculation and analysis of atmospheric attenuation can lay the foundation for the smooth implementation of precipitation radar external calibration experiments.
Available online: October 16, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.072701
Abstract:
In view of the increasing global climate change and extreme weather events, the impact of marine thunderstorms on navigation and offshore operations is becoming more and more serious. However, due to the lack of understanding of the characteristics and mechanisms of marine thunderstorms by forecasters, as well as the scarcity of marine observation data, it is difficult to track and forecast marine thunderstorms. In response to the above problems, this article comprehensively summarizes the latest progress in the field of marine thunderstorm research at home and abroad from the perspective of meteorological forecasters, covering marine thunderstorm monitoring methods and technologies, activity characteristics, and formation mechanisms. It aims to sort out and discuss the current status, development trends, and key issues of global marine thunderstorm research. Based on the review, the future research direction of marine thunderstorms in China is discussed, including strengthening the construction of marine observation systems, building marine thunderstorm data sets, deepening the study of the formation mechanisms of marine thunderstorms, and strengthening the application of artificial intelligence to build accurate prediction models. This article aims to provide meteorological forecasters with research results on marine thunderstorms, in order to better serve the safety of navigation and offshore operations, and reduce the adverse effects of marine thunderstorms.
In view of the increasing global climate change and extreme weather events, the impact of marine thunderstorms on navigation and offshore operations is becoming more and more serious. However, due to the lack of understanding of the characteristics and mechanisms of marine thunderstorms by forecasters, as well as the scarcity of marine observation data, it is difficult to track and forecast marine thunderstorms. In response to the above problems, this article comprehensively summarizes the latest progress in the field of marine thunderstorm research at home and abroad from the perspective of meteorological forecasters, covering marine thunderstorm monitoring methods and technologies, activity characteristics, and formation mechanisms. It aims to sort out and discuss the current status, development trends, and key issues of global marine thunderstorm research. Based on the review, the future research direction of marine thunderstorms in China is discussed, including strengthening the construction of marine observation systems, building marine thunderstorm data sets, deepening the study of the formation mechanisms of marine thunderstorms, and strengthening the application of artificial intelligence to build accurate prediction models. This article aims to provide meteorological forecasters with research results on marine thunderstorms, in order to better serve the safety of navigation and offshore operations, and reduce the adverse effects of marine thunderstorms.
Available online: October 15, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.092701
Abstract:
The causes and predictability of the high-impact large-scale cryogenic freezing rain and snow weather (CFRSW) in east and central China in February 2024 were investigated using the daily temperature and precipitation data from 2,374 stations, the NCEP/NCAR atmospheric circulation reanalysis data and the HadISST data. The results show that: (1) Two CFRSW processes occurred in China in early and late February 2024, and the overlap of the regions was high. The east and central China suffered the most serious freezing rain and snow disaster. (2) The subtropical and mid-high latitude circulation system configuration that influenced the two CFRSW processes were more consistent, the western north Pacific subtropical high (WNPSH) was strong and westward. Siberian high, the South Branch trough and the western north Pacific anticyclone were strong in the same period, forming a strong synergistic effect. The enhancement of the Siberian high led to cold air southward, and the synchronization of the enhancement of South Branch trough and western north Pacific anticyclone to provide abundant water vapor conditions for the east and central China. (3) A moderate-intensity El Ni?o event occurred in the equatorial east-central Pacific from May 2023 to April 2024. In addition, the tropical Indian Ocean and the tropical North Atlantic were abnormally warm in winter. The abnormal SST of the three oceans jointly led to the continuous strength of the WNPSH. This is conducive to the periodic development and enhancement of the anticyclones in the Northwest Pacific Ocean, and provides abundant water vapor conditions for the two CFRSW processes in February. (4) The predictability of the sub-seasonal model for the two processes is about 1～2 weeks, and the prediction skill within 1 week is relatively high. When advanced by more than 2 weeks, the model is unable to accurately predict the anomalous characteristics of the Eurasian mid-high latitude circulation system, resulting in lower predictive ability for the two processes.
The causes and predictability of the high-impact large-scale cryogenic freezing rain and snow weather (CFRSW) in east and central China in February 2024 were investigated using the daily temperature and precipitation data from 2,374 stations, the NCEP/NCAR atmospheric circulation reanalysis data and the HadISST data. The results show that: (1) Two CFRSW processes occurred in China in early and late February 2024, and the overlap of the regions was high. The east and central China suffered the most serious freezing rain and snow disaster. (2) The subtropical and mid-high latitude circulation system configuration that influenced the two CFRSW processes were more consistent, the western north Pacific subtropical high (WNPSH) was strong and westward. Siberian high, the South Branch trough and the western north Pacific anticyclone were strong in the same period, forming a strong synergistic effect. The enhancement of the Siberian high led to cold air southward, and the synchronization of the enhancement of South Branch trough and western north Pacific anticyclone to provide abundant water vapor conditions for the east and central China. (3) A moderate-intensity El Ni?o event occurred in the equatorial east-central Pacific from May 2023 to April 2024. In addition, the tropical Indian Ocean and the tropical North Atlantic were abnormally warm in winter. The abnormal SST of the three oceans jointly led to the continuous strength of the WNPSH. This is conducive to the periodic development and enhancement of the anticyclones in the Northwest Pacific Ocean, and provides abundant water vapor conditions for the two CFRSW processes in February. (4) The predictability of the sub-seasonal model for the two processes is about 1～2 weeks, and the prediction skill within 1 week is relatively high. When advanced by more than 2 weeks, the model is unable to accurately predict the anomalous characteristics of the Eurasian mid-high latitude circulation system, resulting in lower predictive ability for the two processes.
Available online: September 29, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.092401
Abstract:
Thunderstorm gales refer to strong winds with a wind speed ≥17 m·s-1 caused by strong convective weather systems, which are one of meso-scale and micro-scale strong convective weather that causes huge disasters. Understanding their formation mechanisms and conducting accurate nowcasting and early warning are the keys to disaster prevention and mitigation. This paper summarizes the existing studies on the formation mechanisms and nowcasting of thunderstorm gales, including synoptic patterns, environmental characteristics, different formation mechanisms and windstorm morphologies, as well as nowcasting technology. Most thunderstorm gales are generated in supercells, squall lines, and bow echoes through strong downdraft, gust front, momentum transmission, horizontal pressure gradient between outflow and ambient wind, dynamic forcing and superimposed effect of mesoscale vortex, and pumping effect of updraft on low-level warm and moist inflow, etc. On the basis of above review, the difficulties and much-need issues of the formation mechanisms and nowcasting of thunderstorm gales are discussed.
Thunderstorm gales refer to strong winds with a wind speed ≥17 m·s-1 caused by strong convective weather systems, which are one of meso-scale and micro-scale strong convective weather that causes huge disasters. Understanding their formation mechanisms and conducting accurate nowcasting and early warning are the keys to disaster prevention and mitigation. This paper summarizes the existing studies on the formation mechanisms and nowcasting of thunderstorm gales, including synoptic patterns, environmental characteristics, different formation mechanisms and windstorm morphologies, as well as nowcasting technology. Most thunderstorm gales are generated in supercells, squall lines, and bow echoes through strong downdraft, gust front, momentum transmission, horizontal pressure gradient between outflow and ambient wind, dynamic forcing and superimposed effect of mesoscale vortex, and pumping effect of updraft on low-level warm and moist inflow, etc. On the basis of above review, the difficulties and much-need issues of the formation mechanisms and nowcasting of thunderstorm gales are discussed.
Available online: July 15, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.071501
Abstract:
Aerosols and cloud microphysics observational researches have been carried out by aircraft which equipped with cloud physics detection instruments for many years in Hebei Province, China. A series of research results have been obtained and published in the fields of aerosols, cloud condensation nuclei (CCN), clouds and precipitation macro and micro structure characteristics, especially some weather modification catalytic experiments by aircraft. In this paper, the research progress of aerosols and cloud precipitation physical observations over Hebei Province in the recent 20 years were systematically summarized, and the microphysical characteristics of aerosols, CCN and clouds, such as vertical structure, spatial distribution and seasonal variation, were summarized. Four observation field campaigns for aircraft precipitation enhancement operation and the effect test are introduced in detail, and the physical evidence of macro and micro physical characteristics changes in the supercooled water area before and after cloud catalysis is objectively demonstrated. This paper puts forward the future development direction on the basis of summarizing a large number of research results, and provides some suggestions for aerosol-cloud physical aircraft observation and weather modification activities through aircraft catalysis in North China.
Aerosols and cloud microphysics observational researches have been carried out by aircraft which equipped with cloud physics detection instruments for many years in Hebei Province, China. A series of research results have been obtained and published in the fields of aerosols, cloud condensation nuclei (CCN), clouds and precipitation macro and micro structure characteristics, especially some weather modification catalytic experiments by aircraft. In this paper, the research progress of aerosols and cloud precipitation physical observations over Hebei Province in the recent 20 years were systematically summarized, and the microphysical characteristics of aerosols, CCN and clouds, such as vertical structure, spatial distribution and seasonal variation, were summarized. Four observation field campaigns for aircraft precipitation enhancement operation and the effect test are introduced in detail, and the physical evidence of macro and micro physical characteristics changes in the supercooled water area before and after cloud catalysis is objectively demonstrated. This paper puts forward the future development direction on the basis of summarizing a large number of research results, and provides some suggestions for aerosol-cloud physical aircraft observation and weather modification activities through aircraft catalysis in North China.
Available online: June 20, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.022003
Abstract:
Based on forecast products of the European Center for Medium-Range Weather Forecasts - Integrated Forecasting System(ECMWF-IFS) and hourly temperature observation data from the China Meteorological Administration Land Data Assimilation System(CLDAS), an enhanced model named ED-LSTM-FCNN is constructed, incorporating an embedding layer module to handle high-dimensional spatial and temporal features. A fully connected neural network was utilized to integrate various features types and achieve regression prediction of temperature, generating gridded hourly temperature forecast products with a resolution of 0.05°×0.05°. Verification for the 2022 forecast in Hunan Province revealed that the model exhibits a notable capacity to mitigate forecast errors inherent in the numerical model, thereby enhancing the overall forecast stability. The root mean square errors (RMSE) for forecast lead times ranging from 1 to 24 hours exhibit a reduction of 25.4% to 37.7% when compared to ECMWF-IFS and a decrease of 15.8% to 40.0% in comparison to the SCMOC. The model significantly enhances the forecast performance of ECMWF-IFS in spatial prediction, particularly in regions characterized by intricate terrain features. The RMSEs across most areas vary within the range of 1.2 ℃ to 1.6 ℃. The forecast accuracy of the model, with an error margin of ±2 ℃, surpasses 85.0% across various seasons, demonstrating a significant improvement compared to both ECMWF-IFS and SCMOC. The forecasting performance is notably superior, particularly in stable extreme high-temperature weather conditions, when compared to alternative products. In conclusion, this method proved to be effective for high-resolution temperature grid forecasting operations.
Based on forecast products of the European Center for Medium-Range Weather Forecasts - Integrated Forecasting System(ECMWF-IFS) and hourly temperature observation data from the China Meteorological Administration Land Data Assimilation System(CLDAS), an enhanced model named ED-LSTM-FCNN is constructed, incorporating an embedding layer module to handle high-dimensional spatial and temporal features. A fully connected neural network was utilized to integrate various features types and achieve regression prediction of temperature, generating gridded hourly temperature forecast products with a resolution of 0.05°×0.05°. Verification for the 2022 forecast in Hunan Province revealed that the model exhibits a notable capacity to mitigate forecast errors inherent in the numerical model, thereby enhancing the overall forecast stability. The root mean square errors (RMSE) for forecast lead times ranging from 1 to 24 hours exhibit a reduction of 25.4% to 37.7% when compared to ECMWF-IFS and a decrease of 15.8% to 40.0% in comparison to the SCMOC. The model significantly enhances the forecast performance of ECMWF-IFS in spatial prediction, particularly in regions characterized by intricate terrain features. The RMSEs across most areas vary within the range of 1.2 ℃ to 1.6 ℃. The forecast accuracy of the model, with an error margin of ±2 ℃, surpasses 85.0% across various seasons, demonstrating a significant improvement compared to both ECMWF-IFS and SCMOC. The forecasting performance is notably superior, particularly in stable extreme high-temperature weather conditions, when compared to alternative products. In conclusion, this method proved to be effective for high-resolution temperature grid forecasting operations.
Available online: June 05, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.031405
Abstract:
Abstract: Based on the ground observation data of daily precipitation, snow depth, daily mean temperature, daily minimum temperature and weather phenomena in Henan Province from November to March, 1991-2020, the low temperature threshold, the process and duration of cryogenic freezing rain and snow were determined by mathematical statistics. The factors that characterize the intensity of rain and snow and the degree of low temperature were selected to construct the meteorological index of cryogenic freezing rain and snow. The calculation and standardization of the cryogenic freezing rain and snow meteorological index were carried out at each observation station over the past years, and the standard deviation classification method was adopted, combined with the percentage distribution of each interval of the standardized meteorological index and the practical performance. Based on the above operations, the cryogenic freezing rain and snow events were divided into four levels: light, medium, heavy and extra heavy, respectively. The meteorological index and its standardized calculation of cryogenic freezing rain and snow at each observation station were carried out. According to the classification standard, the frequency of cryogenic freezing rain and snow of the multi-year average of each station and the representative stations in the past years were classified and counted. The results showed that: The mountainous area of western Henan is a high incidence area of cryogenic freezing rain and snow, while the basin of southwestern Henan and northwestern Henan are the low incidence areas. The multi-year average frequency of occurrence at all sites showed a decreasing trend from light to extra heavy. There is not a positive correlation between latitude and the frequency of cryogenic freezing rain and snow, and extra-heavy events occur even more frequently at low-latitude sites than at high-latitude and mountain sites.
Abstract: Based on the ground observation data of daily precipitation, snow depth, daily mean temperature, daily minimum temperature and weather phenomena in Henan Province from November to March, 1991-2020, the low temperature threshold, the process and duration of cryogenic freezing rain and snow were determined by mathematical statistics. The factors that characterize the intensity of rain and snow and the degree of low temperature were selected to construct the meteorological index of cryogenic freezing rain and snow. The calculation and standardization of the cryogenic freezing rain and snow meteorological index were carried out at each observation station over the past years, and the standard deviation classification method was adopted, combined with the percentage distribution of each interval of the standardized meteorological index and the practical performance. Based on the above operations, the cryogenic freezing rain and snow events were divided into four levels: light, medium, heavy and extra heavy, respectively. The meteorological index and its standardized calculation of cryogenic freezing rain and snow at each observation station were carried out. According to the classification standard, the frequency of cryogenic freezing rain and snow of the multi-year average of each station and the representative stations in the past years were classified and counted. The results showed that: The mountainous area of western Henan is a high incidence area of cryogenic freezing rain and snow, while the basin of southwestern Henan and northwestern Henan are the low incidence areas. The multi-year average frequency of occurrence at all sites showed a decreasing trend from light to extra heavy. There is not a positive correlation between latitude and the frequency of cryogenic freezing rain and snow, and extra-heavy events occur even more frequently at low-latitude sites than at high-latitude and mountain sites.
Select AllDeselectExport
Display Method:
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.
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.
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.
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.
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(2):133-145, DOI: 10.7519/j.issn.1000-0526.2014.02.001
Abstract:
By using the NCEP reanalysis data, the vapor budget of the area covered by the severe torrential rain over the northeast of North China on 21 July, 2012 is calculated according to the vapor budget equation. The results show that meridional water vapor transportation is dominant while the extremely heavy rain hits Beijing Region, where most moist vapor comes from the southern boundary below 500 hPa. The low level regional moisture convergence is consistent with the time and space when the torrential rain breaks out and develops. Above the middle level the vertical vapor transport is more prominent. Then the variation features of the vapor transport corridors and their moisture contributions are got through the HYSPLIT mode. The backward trajectory analyses illustrate two major vapor transport corridors. The moistest vapor derived from Yellow Sea and East China Sea along the low level make the main moisture contribution during the heavy precipitation. Moisture from the South China Sea and the Bay of Bengal strengthens the water vapor in the region when the heavy rain starts and develops. Also the drier vapor corridor along the high level from the northwest of China plays an important role in this case.
By using the NCEP reanalysis data, the vapor budget of the area covered by the severe torrential rain over the northeast of North China on 21 July, 2012 is calculated according to the vapor budget equation. The results show that meridional water vapor transportation is dominant while the extremely heavy rain hits Beijing Region, where most moist vapor comes from the southern boundary below 500 hPa. The low level regional moisture convergence is consistent with the time and space when the torrential rain breaks out and develops. Above the middle level the vertical vapor transport is more prominent. Then the variation features of the vapor transport corridors and their moisture contributions are got through the HYSPLIT mode. The backward trajectory analyses illustrate two major vapor transport corridors. The moistest vapor derived from Yellow Sea and East China Sea along the low level make the main moisture contribution during the heavy precipitation. Moisture from the South China Sea and the Bay of Bengal strengthens the water vapor in the region when the heavy rain starts and develops. Also the drier vapor corridor along the high level from the northwest of China plays an important role in this case.
2012,38(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.
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(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.
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.
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.
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.
2013,39(9):1163-1170, DOI: 10.7519/j.issn.1000-0526.2013.09.011
Abstract:
Drought and flood have significant impacts on catchment water use and ecological balance. To develop practical drought/flood monitoring indicators that only need a few climate variables, it is fundamentally necessary to explore the relationship between hydrology variables and climate variables for the specific catchment. This study investigates the correlations between lake water level and various time scale climatological indices according to the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI), based on the monthly water level records from Honghu Lake representative gauging stations and the monthly observations of 8 meteorological stations in the Four Lake Basin. The results showed that extreme droughts and floods are primarily controlled by precipitation variability over the Four Lake Basin, and both SPEI and SPI are well related with lake water level of Honghu Lake while the degree of the correlation varies between different seasons and SPEI/SPI time scales, with the highest correlations for rainy summer and autumn months. Generally, the 4-6 month scale SPEI/SPI drought index is most closely correlated with lake water level of Honghu Lake, showing an apparent response of lake water level to the current and former months’ water surplus and deficiency. When compared with the historical time series of monthly average lake water level of Honghu Lake, the 5 month scale SPEI/SPI agrees well with the variability of the lake water level. The response relationship found during the study can not only aid the monitoring and forecasting of flood and drought conditions in the Four Lake Basin based on conventional weather data, but also provides some references for other places of China.
Drought and flood have significant impacts on catchment water use and ecological balance. To develop practical drought/flood monitoring indicators that only need a few climate variables, it is fundamentally necessary to explore the relationship between hydrology variables and climate variables for the specific catchment. This study investigates the correlations between lake water level and various time scale climatological indices according to the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI), based on the monthly water level records from Honghu Lake representative gauging stations and the monthly observations of 8 meteorological stations in the Four Lake Basin. The results showed that extreme droughts and floods are primarily controlled by precipitation variability over the Four Lake Basin, and both SPEI and SPI are well related with lake water level of Honghu Lake while the degree of the correlation varies between different seasons and SPEI/SPI time scales, with the highest correlations for rainy summer and autumn months. Generally, the 4-6 month scale SPEI/SPI drought index is most closely correlated with lake water level of Honghu Lake, showing an apparent response of lake water level to the current and former months’ water surplus and deficiency. When compared with the historical time series of monthly average lake water level of Honghu Lake, the 5 month scale SPEI/SPI agrees well with the variability of the lake water level. The response relationship found during the study can not only aid the monitoring and forecasting of flood and drought conditions in the Four Lake Basin based on conventional weather data, but also provides some references for other places of China.
2011,37(1):122-128, DOI: 10.7519/j.issn.1000-0526.2011.1.017
Abstract:
The following are the main characteristics of the general atmospheric circulation in October 2010. There were two polar vortex centers in the Northern Hemisphere. The circulation presents a four wave pattern in middle high latitudes, in which the strong Ural ridge corresponds to a large 40 gpm positive anomaly area. Strength of the Western Pacific subtropical high is weaker than normal years. The monthly mean temperature (10.1 ℃) is 0.5 ℃ higher than the same period of normal years, and the mean precipitation (42.6 mm) is 15.1% above normal. The major weather events include: 8 precipitation processes occuring, in which a rare heavy rain has struck on Hainan in the first and middle dekad of October; two tropical cyclones generated, with one super typhoon (Chaba, numbered 1013) landed in Fujian; in the last dekad of October, strong cold air outbreak across most areas of China; heavy fog aroused in the central and eastern China.
The following are the main characteristics of the general atmospheric circulation in October 2010. There were two polar vortex centers in the Northern Hemisphere. The circulation presents a four wave pattern in middle high latitudes, in which the strong Ural ridge corresponds to a large 40 gpm positive anomaly area. Strength of the Western Pacific subtropical high is weaker than normal years. The monthly mean temperature (10.1 ℃) is 0.5 ℃ higher than the same period of normal years, and the mean precipitation (42.6 mm) is 15.1% above normal. The major weather events include: 8 precipitation processes occuring, in which a rare heavy rain has struck on Hainan in the first and middle dekad of October; two tropical cyclones generated, with one super typhoon (Chaba, numbered 1013) landed in Fujian; in the last dekad of October, strong cold air outbreak across most areas of China; heavy fog aroused in the central and eastern China.
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.
Mobile website
® 2024 All Rights Reserved
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
ISSN:1000-0526 CN:11-2282/P