ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 51,2025 Issue 1
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- Recommended Topics
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- The Future Projections of Extreme Weather, Climate and Water Events and Strategic Responses
- A Review of Downburst Genesis Mechanism and Warning
- The Pattern Structure and Thermodynamic and Dynamic Processes of Severe Storms Associated with Linear Convective Gales
- Analysis on Extremity and Characteristics of the “21·7” Severe Torrential Rain in Henan Province
- Diagnostic Analysis on Water Vapor and Jet Characteristics of the July 2021 Severe Torrential Rain in Henan Province
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2025,51(1):1-16, 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 has become more and more serious. However, due to the lack of understanding of the characteristics and mechanisms of marine thunderstorms, coupled with 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 mar-ine thunderstorm monitoring methods and technologies, activity characteristics and formation mechanisms for the purpose of sorting and discussing 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. The content of this article can provide research results on marine thunderstorms and better serve the safety of navigation and offshore operations and the reduction of 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 has become more and more serious. However, due to the lack of understanding of the characteristics and mechanisms of marine thunderstorms, coupled with 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 mar-ine thunderstorm monitoring methods and technologies, activity characteristics and formation mechanisms for the purpose of sorting and discussing 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. The content of this article can provide research results on marine thunderstorms and better serve the safety of navigation and offshore operations and the reduction of the adverse effects of marine thunderstorms.
2025,51(1):17-29, 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 China and Central China in February 2024 are investigated with the daily temperature and precipitation data from 2374 stations, the NCEP/NCAR atmospheric circulation reanalysis data and the HadISST data. The results show that the two CFRSW processes occurred in China in early and late February 2024, and the overlap of the disaster-hit regions was high so that East China and Central China suffered the most serious freezing rain and snow disaster. The subtropical and mid-high latitude circulation system configurations that impacted the two CFRSW processes were more consistent, the Northwest Pacific subtropical high was stronger and more westward. Moreover, the Siberian high, the South Branch trough and the Northwest Pacific anticyclone were stronger 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 provided abundant water vapor conditions for East China and Central China. A moderate-intensity El Nino 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 strengthening of the Northwest Pacific subtropical high. This was conductive to the periodic development and enhancement of the anticyclones in the Northwest Pacific Ocean, and provided abundant water vapor conditions for the two CFRSW processes in February 2024. The predictability of the sub-seasonal model for the two processes is about 1-2 weeks ahead of time, and the prediction skill within 1 week is relatively high. When the prediction is 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 China and Central China in February 2024 are investigated with the daily temperature and precipitation data from 2374 stations, the NCEP/NCAR atmospheric circulation reanalysis data and the HadISST data. The results show that the two CFRSW processes occurred in China in early and late February 2024, and the overlap of the disaster-hit regions was high so that East China and Central China suffered the most serious freezing rain and snow disaster. The subtropical and mid-high latitude circulation system configurations that impacted the two CFRSW processes were more consistent, the Northwest Pacific subtropical high was stronger and more westward. Moreover, the Siberian high, the South Branch trough and the Northwest Pacific anticyclone were stronger 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 provided abundant water vapor conditions for East China and Central China. A moderate-intensity El Nino 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 strengthening of the Northwest Pacific subtropical high. This was conductive to the periodic development and enhancement of the anticyclones in the Northwest Pacific Ocean, and provided abundant water vapor conditions for the two CFRSW processes in February 2024. The predictability of the sub-seasonal model for the two processes is about 1-2 weeks ahead of time, and the prediction skill within 1 week is relatively high. When the prediction is 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.
2025,51(1):30-42, DOI: 10.7519/j.issn.1000-0526.2024.120201
Abstract:
Using the 3 h densely-observed radiosonde and the 1 h automatic weather station data obtained from Baolian, Chaoyang and Daxing stations in Beijing from 28 August to 2 September 2016, based on the WRF model and the WRFDA three-dimensional variational assimilation system, this paper conducts assimi-lation experiments on only assimilating densely-observed radiosonde data (S-DA), only assimilating automatic weather station data (A-DA), and simultaneously assimilating the above two types of data (M-DA), to investigate the improvement effect of the three data assimilation schemes in the numerical simulation of the boundary layer in the Beijing Area. The results show that in the vertical direction, the densely-observed radiosonde data play a core role in improving simulation results, which can reduce the root mean square errors of temperature, relative humidity, and wind speed within the boundary layer range by 65%, 61%, and 22%, respectively. The automatic weather station data also contribute 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 experiment are similar to those of the S-DA experiment. In the horizontal direction, the improvement effect of the assimilated automatic weather station data is mainly reflected in a wide range of impact. The effect of densely-observed radiosonde data has strong improvement, but the impact range is small. The advantages of combining the two types of data in the M-DA experiment can make the simulation results closer to the observation results. In terms of assimilation timeliness, the assimilation experiment 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 experiment can extend its effect for the thermal state up to 6 h in forecast, and its effect for the humidity and dynamic structure up to 3 h in forecast. In summary, the simultaneous assimilation of densely-observed radiosonde and automatic weather station data is more effective than assimilating one of the data only. 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 h densely-observed radiosonde and the 1 h automatic weather station data obtained from Baolian, Chaoyang and Daxing stations in Beijing from 28 August to 2 September 2016, based on the WRF model and the WRFDA three-dimensional variational assimilation system, this paper conducts assimi-lation experiments on only assimilating densely-observed radiosonde data (S-DA), only assimilating automatic weather station data (A-DA), and simultaneously assimilating the above two types of data (M-DA), to investigate the improvement effect of the three data assimilation schemes in the numerical simulation of the boundary layer in the Beijing Area. The results show that in the vertical direction, the densely-observed radiosonde data play a core role in improving simulation results, which can reduce the root mean square errors of temperature, relative humidity, and wind speed within the boundary layer range by 65%, 61%, and 22%, respectively. The automatic weather station data also contribute 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 experiment are similar to those of the S-DA experiment. In the horizontal direction, the improvement effect of the assimilated automatic weather station data is mainly reflected in a wide range of impact. The effect of densely-observed radiosonde data has strong improvement, but the impact range is small. The advantages of combining the two types of data in the M-DA experiment can make the simulation results closer to the observation results. In terms of assimilation timeliness, the assimilation experiment 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 experiment can extend its effect for the thermal state up to 6 h in forecast, and its effect for the humidity and dynamic structure up to 3 h in forecast. In summary, the simultaneous assimilation of densely-observed radiosonde and automatic weather station data is more effective than assimilating one of the data only. 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.
2025,51(1):43-56, DOI: 10.7519/j.issn.1000-0526.2024.113001
Abstract:
To study the characteristics of downburst under weak vertical wind shear, based on the SA Doppler weather radar, sounding and surface (10 m) maximum wind data and the cloud images from stationary meteorological satellites, we selected 381 downburst events that occurred under weak vertical wind shear from June to September in 2019-2020 in Jiangsu Province and divided them into three categories according to the scales of microburst, macroburst and downburst cluster. The statistical results show that 64.9% of thunderstorm days in Jiangsu from June to September are accompanied by downbursts, 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, and they all tend to occur in the time period of 15:00-16:00 BT. According to 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 downburst samples reach the standard of disaster gale (extreme radial velocity at low elevation reaches 25 m·s-1 or radial velocity difference of divergence couplets attains 40 m·s-1). The average surface maximum wind caused by downburst observed by surface meteorological stations is 15.5 m·s-1, indicating that disaster-causing potential of downburst is not significant. The low-elevation radial velocity modes of downburst are dominated by divergence vel-ocity couplet (73.3%), but the majorities are asymmetric while only 6.1% for symmetrical divergence velocity couplet. There are 26.7% of downburst characterized by strong wind at low elevation.
To study the characteristics of downburst under weak vertical wind shear, based on the SA Doppler weather radar, sounding and surface (10 m) maximum wind data and the cloud images from stationary meteorological satellites, we selected 381 downburst events that occurred under weak vertical wind shear from June to September in 2019-2020 in Jiangsu Province and divided them into three categories according to the scales of microburst, macroburst and downburst cluster. The statistical results show that 64.9% of thunderstorm days in Jiangsu from June to September are accompanied by downbursts, 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, and they all tend to occur in the time period of 15:00-16:00 BT. According to 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 downburst samples reach the standard of disaster gale (extreme radial velocity at low elevation reaches 25 m·s-1 or radial velocity difference of divergence couplets attains 40 m·s-1). The average surface maximum wind caused by downburst observed by surface meteorological stations is 15.5 m·s-1, indicating that disaster-causing potential of downburst is not significant. The low-elevation radial velocity modes of downburst are dominated by divergence vel-ocity couplet (73.3%), but the majorities are asymmetric while only 6.1% for symmetrical divergence velocity couplet. There are 26.7% of downburst characterized by strong wind at low elevation.
2025,51(1):57-67, DOI: 10.7519/j.issn.10000526.2024.080501
Abstract:
In the complex terrain of Sichuan Region, although the frequency of thunderstorm gale is relatively low, its impact is significant. There are few objective forecast products of the thunderstorm gale, and even if there are, the time resolution is lower. In order to further improve the accuracy of thunderstorm gale forecasting under complex terrain in Sichuan, in this article we comprehensively consider terrain factors, model physical quantity factors and time factors. According to the altitude, Sichuan is divided into highaltitude and low altitude areas. Based on the data from 2018 to 2021 and three machine learning methods of random forest, adaptive boosting and extreme random tree, we construct a thunderstorm gale prediction model and make a forecast for the 2022 thunderstorm gales obtaining a 3 h thunderstorm gale potential forecast. Then, based on the climate background, we downscale the 3 h forecast time to 1 h, and make a 0-12 h hourly thunderstorm gale forecast. At the same time, the forecasting effect is tested. The results show that, the adaptive boosting method of 3 h thunderstorm gale forecast has the best effect. The longtime and individual case tests show that the 0-12 h hourly thunderstorm gale forecast product obtained by the adaptive boosting method is superior to the forecasts of National Meteorological Centre with the TS score increased from 0.0104 to 0.0595, and the false alarm rate decreased from 0.988 to 0.808. This indicates that the adaptive boosting method has a higher application value in forecasting operation application value.
In the complex terrain of Sichuan Region, although the frequency of thunderstorm gale is relatively low, its impact is significant. There are few objective forecast products of the thunderstorm gale, and even if there are, the time resolution is lower. In order to further improve the accuracy of thunderstorm gale forecasting under complex terrain in Sichuan, in this article we comprehensively consider terrain factors, model physical quantity factors and time factors. According to the altitude, Sichuan is divided into highaltitude and low altitude areas. Based on the data from 2018 to 2021 and three machine learning methods of random forest, adaptive boosting and extreme random tree, we construct a thunderstorm gale prediction model and make a forecast for the 2022 thunderstorm gales obtaining a 3 h thunderstorm gale potential forecast. Then, based on the climate background, we downscale the 3 h forecast time to 1 h, and make a 0-12 h hourly thunderstorm gale forecast. At the same time, the forecasting effect is tested. The results show that, the adaptive boosting method of 3 h thunderstorm gale forecast has the best effect. The longtime and individual case tests show that the 0-12 h hourly thunderstorm gale forecast product obtained by the adaptive boosting method is superior to the forecasts of National Meteorological Centre with the TS score increased from 0.0104 to 0.0595, and the false alarm rate decreased from 0.988 to 0.808. This indicates that the adaptive boosting method has a higher application value in forecasting operation application value.
2025,51(1):68-84, DOI: 10.7519/j.issn.1000-0526.2024.111201
Abstract:
In order to improve the monitoring and early warning capabilities for autumn hail, based on the dual-polarization radar and FY-4A satellite data, this paper analyzed a rare autumn severe hail process that occurred in Hunan Province in November 2023, and discussed its early warning characteristics. The findings are as follows: (1) The severe hail process was produced by supercell hailstorms. In the hail stage, the bottom of the strong echo center with horizontal reflectivity factor ZH ≥65 dBz was close to the ground, the correlation coefficient (CC) was lower than 0.9, the specific differential phase (KDP) was a cavity, and the differential reflectivity factor (ZDR) was -3-0 dB. These corresponded to the condition for the fall of large hailstone with diameter ≥ 5 cm, and matched with the observation. The rise and fall of the ZDR column can characterize the strengthening and weakening of updraft, and the ZDR with CC can identify three body scatter signature (TBSS) and side lobe characteristics. (2) The area of strong echo and the height of centroid were good indicators for different development stages of supercell. Combined with monitoring, the lead time of early warning of hail can be improved by more than 12 min. During this severe hail process, the length of TBSS caused by the supercell reached 73 km which is rarely seen. The emergence of TBSS and the divergence of the storm top showed a significant weakening trend, which was 17 min more earlier than the occurrence time of hail. (3) Hail and thunderstorm gale appeared 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 indicators of the characteristic parameters of autumn hail cloud by FY-4A satellite. (4) The TBB maximum lapse rate can provide at least 11 min of advance warning for impending hail. The brightness temperature difference of 13.3 μm and 10.8 μm channel is the most sensitive to the development and weakening of hail clouds. The brightness temperature difference of 6.5 μm and 10.8 μm channels is more sensitive to the related conditions before and after the hail passes through the hit area than other brightness temperature differences among the single-station convection monitoring indicators.
In order to improve the monitoring and early warning capabilities for autumn hail, based on the dual-polarization radar and FY-4A satellite data, this paper analyzed a rare autumn severe hail process that occurred in Hunan Province in November 2023, and discussed its early warning characteristics. The findings are as follows: (1) The severe hail process was produced by supercell hailstorms. In the hail stage, the bottom of the strong echo center with horizontal reflectivity factor ZH ≥65 dBz was close to the ground, the correlation coefficient (CC) was lower than 0.9, the specific differential phase (KDP) was a cavity, and the differential reflectivity factor (ZDR) was -3-0 dB. These corresponded to the condition for the fall of large hailstone with diameter ≥ 5 cm, and matched with the observation. The rise and fall of the ZDR column can characterize the strengthening and weakening of updraft, and the ZDR with CC can identify three body scatter signature (TBSS) and side lobe characteristics. (2) The area of strong echo and the height of centroid were good indicators for different development stages of supercell. Combined with monitoring, the lead time of early warning of hail can be improved by more than 12 min. During this severe hail process, the length of TBSS caused by the supercell reached 73 km which is rarely seen. The emergence of TBSS and the divergence of the storm top showed a significant weakening trend, which was 17 min more earlier than the occurrence time of hail. (3) Hail and thunderstorm gale appeared 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 indicators of the characteristic parameters of autumn hail cloud by FY-4A satellite. (4) The TBB maximum lapse rate can provide at least 11 min of advance warning for impending hail. The brightness temperature difference of 13.3 μm and 10.8 μm channel is the most sensitive to the development and weakening of hail clouds. The brightness temperature difference of 6.5 μm and 10.8 μm channels is more sensitive to the related conditions before and after the hail passes through the hit area than other brightness temperature differences among the single-station convection monitoring indicators.
2025,51(1):85-96, DOI: 10.7519/j.issn.1000-0526.2024.100801
Abstract:
Based on dense ball sound data, dense field surface observation, ERA5 and the Linhe New Generation Weather Radar data, detailed analysis is conducted on the boundary layer convergence lines (BLCL) formed by the surface differences between the Hetao irrigation area and the Kubuqi Desert in Hetao Area of the Yellow River in July and August 2022, and also on the role of BLCL in convection triggering. The results indicate that the BLCL in the Hetao Area was formed by the combined influence of surface differences, boundary layer atmospheric circulation and complex terrain, and mainly occurred in the Kubuqi Desert which lies in the southeast of the Hetao irrigation area, and the length of BLCL ranged from 100 to 200 km. The BLCL was a shallow system with vertical thickness of approximately 1000 to 1100 m. The daily variation of BLCL was significant, with a high incidence from 12:00 BT to 17:00 BT, accounting for 80%. The probability of BLCL formation in July and August was as high as 60%, and 39% of BLCL could trigger convection. The prediction indicators about the formation of BLCL are as follows.The temperature in Hangjinhou Banner in Hetao irrigation area is 2.5 ℃ lower than that in Habailaigeng in Kubuqi Desert, with dew point temperature higher than 6℃ and relative humidity higher than 20%. Continuous strong southerly winds blow in the Kubuqi Desert and Mu Us Sandy Land in Hetao Area, with maximum wind of 10 m above the surface being stronger than 4 m·s-1. The sea level pressure is low in the west and high in the east. A dense isobaric zone is in the curved section of Yellow River and the pressure gradient is 3-4 hPa·100 km-1. The formation of BLCL is of great significance to the convection triggering in this area, which is manifested in convection triggering, strengthening, and organization. Under different environmental conditions and weather system superposition configurations, the BLCL could trigger local convection, organized severe convection, torrential rain in Hetao Area. The generation and convective triggering of Hetao BLCL in this specific area are closely related to the distribution characteristics of rapid increase in precipitation from west to east in Hetao Area.
Based on dense ball sound data, dense field surface observation, ERA5 and the Linhe New Generation Weather Radar data, detailed analysis is conducted on the boundary layer convergence lines (BLCL) formed by the surface differences between the Hetao irrigation area and the Kubuqi Desert in Hetao Area of the Yellow River in July and August 2022, and also on the role of BLCL in convection triggering. The results indicate that the BLCL in the Hetao Area was formed by the combined influence of surface differences, boundary layer atmospheric circulation and complex terrain, and mainly occurred in the Kubuqi Desert which lies in the southeast of the Hetao irrigation area, and the length of BLCL ranged from 100 to 200 km. The BLCL was a shallow system with vertical thickness of approximately 1000 to 1100 m. The daily variation of BLCL was significant, with a high incidence from 12:00 BT to 17:00 BT, accounting for 80%. The probability of BLCL formation in July and August was as high as 60%, and 39% of BLCL could trigger convection. The prediction indicators about the formation of BLCL are as follows.The temperature in Hangjinhou Banner in Hetao irrigation area is 2.5 ℃ lower than that in Habailaigeng in Kubuqi Desert, with dew point temperature higher than 6℃ and relative humidity higher than 20%. Continuous strong southerly winds blow in the Kubuqi Desert and Mu Us Sandy Land in Hetao Area, with maximum wind of 10 m above the surface being stronger than 4 m·s-1. The sea level pressure is low in the west and high in the east. A dense isobaric zone is in the curved section of Yellow River and the pressure gradient is 3-4 hPa·100 km-1. The formation of BLCL is of great significance to the convection triggering in this area, which is manifested in convection triggering, strengthening, and organization. Under different environmental conditions and weather system superposition configurations, the BLCL could trigger local convection, organized severe convection, torrential rain in Hetao Area. The generation and convective triggering of Hetao BLCL in this specific area are closely related to the distribution characteristics of rapid increase in precipitation from west to east in Hetao Area.
2025,51(1):97-109, DOI: 10.7519/j.issn.1000-0526.2024.100901
Abstract:
In order to solve the problem of meteorological service for transportation operation in areas with a few observation stations, three typical regions in northern China (Beijing-Tianjin, Shaanxi-Gansu and Qinghai) are selected. The data used include the transportation weather observation data, the surface data from China Meteorological Administration Land Data Assimilation System (CLDAS V2.0) and Multi-source Precipitation Analysis System (CMPAS), as well as surface short wave and long wave radiation retrieval products from FY-4A. The change characteristics of road surface temperature and its relationship with environmental meteorological factors are analyzed. Three methods (linear regression, random forest and deep neural network) are employed to construct a 1 h updated real-time road surface temperature model, and the effects of model results from different methods and different data combinations are tested. Besides, the spatial generalization ability of the model is also explored. The results show that the road surface temperature is significantly correlated to the environmental meteorological factors, but show different feactures in different regions, seasons and time periods. The independent test shows that there is no much difference among the model results based on different methods. All the model results can well reproduce the daily changes of road surface high temperature in summer and road surface low temperature in winter. The mean 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 high temperature observation model results in summer. The model has good spatial adaptability. However, compared with the model constructed according to local observations, the error of the model using data from nearby traffic stations in the same climate region shows an increasing trend at different degrees, of which the error increasing in Beijing-Tianjin region is the smallest.
In order to solve the problem of meteorological service for transportation operation in areas with a few observation stations, three typical regions in northern China (Beijing-Tianjin, Shaanxi-Gansu and Qinghai) are selected. The data used include the transportation weather observation data, the surface data from China Meteorological Administration Land Data Assimilation System (CLDAS V2.0) and Multi-source Precipitation Analysis System (CMPAS), as well as surface short wave and long wave radiation retrieval products from FY-4A. The change characteristics of road surface temperature and its relationship with environmental meteorological factors are analyzed. Three methods (linear regression, random forest and deep neural network) are employed to construct a 1 h updated real-time road surface temperature model, and the effects of model results from different methods and different data combinations are tested. Besides, the spatial generalization ability of the model is also explored. The results show that the road surface temperature is significantly correlated to the environmental meteorological factors, but show different feactures in different regions, seasons and time periods. The independent test shows that there is no much difference among the model results based on different methods. All the model results can well reproduce the daily changes of road surface high temperature in summer and road surface low temperature in winter. The mean 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 high temperature observation model results in summer. The model has good spatial adaptability. However, compared with the model constructed according to local observations, the error of the model using data from nearby traffic stations in the same climate region shows an increasing trend at different degrees, of which the error increasing in Beijing-Tianjin region is the smallest.
2025,51(1):110-121, DOI: 10.7519/j.issn.1000 0526.2024.111301
Abstract:
In the summer of 2024, the overall climate of China was characterized by high temperature with more rainfall. The national average summer temperature ranked the first highest since 1961. The high temperature processes occurred earlier than normal, influenced more regions and had strong extremes. The overall precipitation was generally above normal, with a distribution of more in eastern China and less in western China. The precipitation was more than the normal by 50% to 100% in the southern part of Northeast China, central Inner Mongolia, eastern part of North China, northern part of East China, northern and southwestern parts of Central China, and eastern part of Northwest China. During this summer time, both the generated typhoons and the landfall typhoons were less than normal. The moderate intensity El Nino which began in May 2023 ended in May 2024 and transitioned to La Nina. At the same time, since the winter of 2023/2024, sea surface temperatures in the tropical Indian Ocean and North Atlantic have been at historical highs. The unusual distribution of tropical sea temperatures has been conducive to strengthening the Western Pacific subtropical high, which transported abundant moisture from Pacific Ocean and Indian Ocean to eastern China, resulting in widespread precipitation and frequent heavy precipitation processes in the eastern monsoon region of China.
In the summer of 2024, the overall climate of China was characterized by high temperature with more rainfall. The national average summer temperature ranked the first highest since 1961. The high temperature processes occurred earlier than normal, influenced more regions and had strong extremes. The overall precipitation was generally above normal, with a distribution of more in eastern China and less in western China. The precipitation was more than the normal by 50% to 100% in the southern part of Northeast China, central Inner Mongolia, eastern part of North China, northern part of East China, northern and southwestern parts of Central China, and eastern part of Northwest China. During this summer time, both the generated typhoons and the landfall typhoons were less than normal. The moderate intensity El Nino which began in May 2023 ended in May 2024 and transitioned to La Nina. At the same time, since the winter of 2023/2024, sea surface temperatures in the tropical Indian Ocean and North Atlantic have been at historical highs. The unusual distribution of tropical sea temperatures has been conducive to strengthening the Western Pacific subtropical high, which transported abundant moisture from Pacific Ocean and Indian Ocean to eastern China, resulting in widespread precipitation and frequent heavy precipitation processes in the eastern monsoon region of China.
2025,51(1):122-128, DOI: 10.7519/j.issn.1000-0526.2024.120301
Abstract:
The main characteristics of the general atmospheric circulation in October 2024 are that the polar vortex was distributed in a multipolar pattern. The mid- and high- latitude circulation in the Northern Hemisphere presented a multi-wave distribution, while in the Eurasian region it presented a “two troughs and one ridge” pattern. The Western Pacific subtropical high was stronger and the location was more westward and northward. In October, the monthly mean temperature was 11.6℃, 1.0℃ higher than that of the same period in normal years (10.6℃). The monthly average precipitation was 39.0 mm, 10% more than the normal (35.6 mm). During this month, there were six cold air processes, five major precipitation processes, and three typhoons affecting China. From September 29 to October 3, the cold air process was a national cold wave, and the three main precipitation processes were related to typhoons.
The main characteristics of the general atmospheric circulation in October 2024 are that the polar vortex was distributed in a multipolar pattern. The mid- and high- latitude circulation in the Northern Hemisphere presented a multi-wave distribution, while in the Eurasian region it presented a “two troughs and one ridge” pattern. The Western Pacific subtropical high was stronger and the location was more westward and northward. In October, the monthly mean temperature was 11.6℃, 1.0℃ higher than that of the same period in normal years (10.6℃). The monthly average precipitation was 39.0 mm, 10% more than the normal (35.6 mm). During this month, there were six cold air processes, five major precipitation processes, and three typhoons affecting China. From September 29 to October 3, the cold air process was a national cold wave, and the three main precipitation processes were related to typhoons.
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Available online: February 19, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.021801
Abstract:
Based on the hourly precipitation data of 122 national meteorological stations in Shandong from 1966 to 2023, the frequency variation of heavy precipitation are analyzed. Different marginal distribution functions are used to fit the duration and amount of precipitation and the change patterns of the return periods of heavy precipitation with different durations based on Copula function are investigated. The results are as followed. There is a significant dependence relation between the duration and amount of heavy precipitation, which can be fitted well using generalized extreme values and logarithmic normal distribution functions. The Gumbel Copula and Clayton Copula functions are suitable for portraying the dependence structure of the binary variables of the short-duration heavy precipitation in Shandong, while the Clayton Copula function is more appropriate when the precipitation lasts more than 8 h. The return period estimated by daily precipitation may seriously underestimate the hazard of short-duration heavy precipitation. For a short-duration heavy precipitation event under the same hazard-bearing condition, the shorter the duration, the longer the joint return period. The high-value areas of joint return period estimated by the Copula function gradually narrow down from the east and the south of Shandong to the east of Shandong with the increase of precipitation duration, and especially, the hazard of heavy precipitation that comes along once every 60 years is higher in the east and the south of Shandong. This method can more scientifically describe the disaster risks of heavy precipitation in different scenarios, especially in the short-duration heavy precipitation scenario, providing scientific reference for disaster prevention and mitigation planning and disaster risk managing in Shandong.
Based on the hourly precipitation data of 122 national meteorological stations in Shandong from 1966 to 2023, the frequency variation of heavy precipitation are analyzed. Different marginal distribution functions are used to fit the duration and amount of precipitation and the change patterns of the return periods of heavy precipitation with different durations based on Copula function are investigated. The results are as followed. There is a significant dependence relation between the duration and amount of heavy precipitation, which can be fitted well using generalized extreme values and logarithmic normal distribution functions. The Gumbel Copula and Clayton Copula functions are suitable for portraying the dependence structure of the binary variables of the short-duration heavy precipitation in Shandong, while the Clayton Copula function is more appropriate when the precipitation lasts more than 8 h. The return period estimated by daily precipitation may seriously underestimate the hazard of short-duration heavy precipitation. For a short-duration heavy precipitation event under the same hazard-bearing condition, the shorter the duration, the longer the joint return period. The high-value areas of joint return period estimated by the Copula function gradually narrow down from the east and the south of Shandong to the east of Shandong with the increase of precipitation duration, and especially, the hazard of heavy precipitation that comes along once every 60 years is higher in the east and the south of Shandong. This method can more scientifically describe the disaster risks of heavy precipitation in different scenarios, especially in the short-duration heavy precipitation scenario, providing scientific reference for disaster prevention and mitigation planning and disaster risk managing in Shandong.
Available online: February 19, 2025 , DOI: 10.7519/j.issn.1000-0526.2024.122703
Abstract:
Based on the observation data of Guyuan C-band Doppler weather radar and X-band dual polarization radar, combined with ERA5 hourly reanalysis, Himawari-8 satellite, automatic weather station and conventional observation data, the causation and radar observation characteristics of a local outsize hail (diameter ≥ 5 cm) event which occurred in Liupan Moutains area of Ningxia on 12 July 2021 is analyzed. The results show that: (1) The supercell storm formed by the merger and development of multicell storm caused the occurrence of outsize hail. The mesoscale ground convergence line, mesoscale cyclone and local circulation in Liupan Moutains area were the main triggering and enhancing systems of mesoscale convective systems (MCS), and also affected the movement direction of MCS. (2) When the large hail occured, the C-band radar composite reflectivity (Z) ≥ 65 dBZ, three-body scatter spike (TBSS) length ≥ 20 km, vertically integrated liquid water content (VIL) ≥ 40 kg·m-2. The cross-correlation coefficient (CC) in the high-value area of the low layer horizontal reflectivity (ZH) of X-band radar was less than 0.8, and the differential reflectivity (ZDR) and specific differential phase (KDP) of the mid to high layer ZH high-value area were negative and CC ＜ 0.8. (3) When the outsize hail occured, Z ≥ 70 dBZ, TBSS length ≥ 30 km, VIL ≥ 50 kg·m-2 for the C-band radar. CC in the low layer ZH high-value area of the X-band radar was less than 0.6 and the "hole" formed in the area with CC ＜ 0.5 helped to identify the area and altitude of outsize hail in the air. (4) ZDR columns and CC rings near the bounded weak echo zone could indicate the position of strong updrafts in the middle and upper layers of supercell. ZH and dual polarization parameter characteristics had good indicative significance for the identification and warning of different hail sizes.
Based on the observation data of Guyuan C-band Doppler weather radar and X-band dual polarization radar, combined with ERA5 hourly reanalysis, Himawari-8 satellite, automatic weather station and conventional observation data, the causation and radar observation characteristics of a local outsize hail (diameter ≥ 5 cm) event which occurred in Liupan Moutains area of Ningxia on 12 July 2021 is analyzed. The results show that: (1) The supercell storm formed by the merger and development of multicell storm caused the occurrence of outsize hail. The mesoscale ground convergence line, mesoscale cyclone and local circulation in Liupan Moutains area were the main triggering and enhancing systems of mesoscale convective systems (MCS), and also affected the movement direction of MCS. (2) When the large hail occured, the C-band radar composite reflectivity (Z) ≥ 65 dBZ, three-body scatter spike (TBSS) length ≥ 20 km, vertically integrated liquid water content (VIL) ≥ 40 kg·m-2. The cross-correlation coefficient (CC) in the high-value area of the low layer horizontal reflectivity (ZH) of X-band radar was less than 0.8, and the differential reflectivity (ZDR) and specific differential phase (KDP) of the mid to high layer ZH high-value area were negative and CC ＜ 0.8. (3) When the outsize hail occured, Z ≥ 70 dBZ, TBSS length ≥ 30 km, VIL ≥ 50 kg·m-2 for the C-band radar. CC in the low layer ZH high-value area of the X-band radar was less than 0.6 and the "hole" formed in the area with CC ＜ 0.5 helped to identify the area and altitude of outsize hail in the air. (4) ZDR columns and CC rings near the bounded weak echo zone could indicate the position of strong updrafts in the middle and upper layers of supercell. ZH and dual polarization parameter characteristics had good indicative significance for the identification and warning of different hail sizes.
Available online: February 18, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.021601
Abstract:
Based on the parallel observation data of GTS12 and GTS1 radiosondes from 89 high altitude meteorological observation stations in China and the model forecast field data of CMA-GFS, a comparative analysis and evaluation of the observation data of the two radiosondes on each mandatory level were conducted. The results show that the GTS12 radiosonde and GTS1 radiosonde have good consistency in temperature and geopotential height observation data, the absolute value of bias of temperature and geopotential height are less than 0.5 ℃ and 30.0 gpm except for a few mandatory levels. The relative humidity observation data of GTS12 radiosonde is about4.6 % larger than that of GTS1 radiosonde. For the stability of observation data, there is not much difference between the two types of radiosondes on the middle and lower mandatory levels. On the upper mandatory levels, the temperature and geopotential height of the GTS12 radiosonde are significantly better than those of the GTS1 radiosonde, but the relative humidity is slightly worse than that of the GTS1 radiosonde. The absolute average bias of temperature observed by GTS12 radiosonde and GTS1 radiosonde relative to the CMA-GFS model data is about 0.34 ℃ and 0.44 ℃, respectively. The average root mean square error is about 1.23 ℃ and 1.31 ℃, and the average related coefficient is about 0.908 and 0.916, respectively. The corresponding of geopotential heights are 11.05 gpm and 14.97 gpm, 18.76 gpm and 25.16 gpm, 0.948 and 0.934. The corresponding of relative humidity are 5.26% and 8.59%, 16.19% and 18.44%, 0.687 and 0.627. indicating that the consistency between the observation data of the GTS12 radiosonde and the CMA-GFS model data is better than that of the GTS1 radiosonde.
Based on the parallel observation data of GTS12 and GTS1 radiosondes from 89 high altitude meteorological observation stations in China and the model forecast field data of CMA-GFS, a comparative analysis and evaluation of the observation data of the two radiosondes on each mandatory level were conducted. The results show that the GTS12 radiosonde and GTS1 radiosonde have good consistency in temperature and geopotential height observation data, the absolute value of bias of temperature and geopotential height are less than 0.5 ℃ and 30.0 gpm except for a few mandatory levels. The relative humidity observation data of GTS12 radiosonde is about4.6 % larger than that of GTS1 radiosonde. For the stability of observation data, there is not much difference between the two types of radiosondes on the middle and lower mandatory levels. On the upper mandatory levels, the temperature and geopotential height of the GTS12 radiosonde are significantly better than those of the GTS1 radiosonde, but the relative humidity is slightly worse than that of the GTS1 radiosonde. The absolute average bias of temperature observed by GTS12 radiosonde and GTS1 radiosonde relative to the CMA-GFS model data is about 0.34 ℃ and 0.44 ℃, respectively. The average root mean square error is about 1.23 ℃ and 1.31 ℃, and the average related coefficient is about 0.908 and 0.916, respectively. The corresponding of geopotential heights are 11.05 gpm and 14.97 gpm, 18.76 gpm and 25.16 gpm, 0.948 and 0.934. The corresponding of relative humidity are 5.26% and 8.59%, 16.19% and 18.44%, 0.687 and 0.627. indicating that the consistency between the observation data of the GTS12 radiosonde and the CMA-GFS model data is better than that of the GTS1 radiosonde.
Available online: February 18, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.011603
Abstract:
On August 13, 2022, a local severe convection occurred near the coast of Shanghai under the control of Western Pacific subtropical high. This event displayed characteristics of a short life span, strong local manifestation, and high intensity. Using data from minute-level ground automatic weather stations, FY-4A geostationary meteorological satellite visible light cloud images, and dual-polarization radar reflectivity factor, a study was conducted on the short-range forecasting techniques and causes of this local strong convection, employing diagnostic variables such as Q vector, perturbation dew point temperature and perturbation temperature. The findings are as follows:(1) The occurrence of precipitation at the ground level was identified as the sign of local strong convective events. By analyzing radar reflectivity factor, satellite visible light cloud images, and Q vector divergence combined with perturbation dew point temperature and perturbation temperature data from ground automatic weather stations, advanced warnings of the convective event could be issued 23, 70, and 100 minutes in advance, respectively. This integrated monitoring and mutual verification of the atmospheric, satellite, and ground observations not only improved the lead time of early warnings for local severe convection but also reduced missed detections. (2) Under the control of the Western Pacific subtropical high-pressure system, temperatures exceeding 35 ℃, combined with the perturbations in temperature and dew point near the urban area, provided favorable thermodynamic conditions for the initiation of deep convection. Simultaneously, differences in land and water underlying characteristics led to higher temperatures on urban land compared to the adjacent Yangtze River water, generating onshore winds. On one hand, this process experienced abrupt changes in land-water underlying characteristics and complex urban land surfaces, causing convergence of wind direction and speed. On the other hand, the convergence of warm and cold air led to atmospheric instability, providing favorable local dynamic forcing conditions. (3) Further analysis reveals that the appearance of significant Q vector divergence convergence at the surface, persisting until surface precipitation occurs, indicates the generation of vertical upward motion due to the dynamic and thermal forcing at the surface. Furthermore, the interaction between the sea breeze front and the convergence-induced updrafts from the urban heat island results in local severe convection.
On August 13, 2022, a local severe convection occurred near the coast of Shanghai under the control of Western Pacific subtropical high. This event displayed characteristics of a short life span, strong local manifestation, and high intensity. Using data from minute-level ground automatic weather stations, FY-4A geostationary meteorological satellite visible light cloud images, and dual-polarization radar reflectivity factor, a study was conducted on the short-range forecasting techniques and causes of this local strong convection, employing diagnostic variables such as Q vector, perturbation dew point temperature and perturbation temperature. The findings are as follows:(1) The occurrence of precipitation at the ground level was identified as the sign of local strong convective events. By analyzing radar reflectivity factor, satellite visible light cloud images, and Q vector divergence combined with perturbation dew point temperature and perturbation temperature data from ground automatic weather stations, advanced warnings of the convective event could be issued 23, 70, and 100 minutes in advance, respectively. This integrated monitoring and mutual verification of the atmospheric, satellite, and ground observations not only improved the lead time of early warnings for local severe convection but also reduced missed detections. (2) Under the control of the Western Pacific subtropical high-pressure system, temperatures exceeding 35 ℃, combined with the perturbations in temperature and dew point near the urban area, provided favorable thermodynamic conditions for the initiation of deep convection. Simultaneously, differences in land and water underlying characteristics led to higher temperatures on urban land compared to the adjacent Yangtze River water, generating onshore winds. On one hand, this process experienced abrupt changes in land-water underlying characteristics and complex urban land surfaces, causing convergence of wind direction and speed. On the other hand, the convergence of warm and cold air led to atmospheric instability, providing favorable local dynamic forcing conditions. (3) Further analysis reveals that the appearance of significant Q vector divergence convergence at the surface, persisting until surface precipitation occurs, indicates the generation of vertical upward motion due to the dynamic and thermal forcing at the surface. Furthermore, the interaction between the sea breeze front and the convergence-induced updrafts from the urban heat island results in local severe convection.
Available online: February 16, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.021401
Abstract:
Based on the weather radar equation, identify the key factors that affect the accuracy of weather radar echo intensity measurement. Radar transmission power is the key variable that is most prone to fluctuations in radar performance parameters, which affects the accuracy of radar measurement; The dynamic range of the receiver is a key indicator for measuring the stability of the receiving channel, which directly affects the measurement results of the echo power. An excellent weather radar system should have functions such as online monitoring, calibration, and correction of key performance parameters. This paper statistically analyzed data samples accumulated over the years from 12 networked radars in Guangdong, and tested the effectiveness of CINRAD/SA-D radar intensity calibration and online correction; The necessity of offline calibration of networked radar is demonstrated through the comparison and stability analysis of key performance parameters. Additionally, the first volume scan data collected when th
Based on the weather radar equation, identify the key factors that affect the accuracy of weather radar echo intensity measurement. Radar transmission power is the key variable that is most prone to fluctuations in radar performance parameters, which affects the accuracy of radar measurement; The dynamic range of the receiver is a key indicator for measuring the stability of the receiving channel, which directly affects the measurement results of the echo power. An excellent weather radar system should have functions such as online monitoring, calibration, and correction of key performance parameters. This paper statistically analyzed data samples accumulated over the years from 12 networked radars in Guangdong, and tested the effectiveness of CINRAD/SA-D radar intensity calibration and online correction; The necessity of offline calibration of networked radar is demonstrated through the comparison and stability analysis of key performance parameters. Additionally, the first volume scan data collected when th
Available online: February 13, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.011501
Abstract:
During May 21 to June 21 in 2022, the strongest dragon-boat precipitation process in the last decade occurred in South China. The extreme dragon-boat precipitation process, with a large cumulative rainfall and frequent heavy rainfall processes, caused significant economic losses. In this paper, two operational models, TRAMS and ECMWF, which are commonly used by forecasters in South China, are selected to divide the torrential rain during dragon-boat precipitation into front-zone torrential rain and warm-sector torrential rain, and are verified and evaluated, in order to understand the characteristics of the two models’ biases for the front-zone torrential rain and warm-sector torrential rain under the background of the extreme dragon-boat precipitation. Compared with the traditional point-to-point method, the MODE method can effectively avoid the phenomenon of high false alarm ratio caused by precipitation position deviation in the model. Further analysis of the number, position, precipitation area and intensity of torrential rain objects based on MODE method shows that the high-resolution model TRAMS has better ability to identify and match torrential rain objects than the global model ECMWF. The position prediction of torrential rain by TRAMS mostly has a eastward bias, while ECMWF has a northward bias. The deviations in precipitation position are closely related to the differences in the forecast bias of the two models for low-level southwesterly flow. The area prediction of the front-zone torrential rain by TRAMS is close to the observation, while the forecast area of warm-sector torrential rain is large. The forecast areas of ECMWF for both front-zone torrential rain and warm-sector torrential rain are small. The prediction of torrential rain intensity and extreme value by TRAMS is closer to the observation than that by ECMWF, but it still underestimates the extreme precipitation. This study can provide new experience for forecasters to understand the prediction biases of different operational models for dragon-boat precipitation process. It also has reference value for model developers to further carry out research on error source diagnosis and technical improvement of TRAMS.
During May 21 to June 21 in 2022, the strongest dragon-boat precipitation process in the last decade occurred in South China. The extreme dragon-boat precipitation process, with a large cumulative rainfall and frequent heavy rainfall processes, caused significant economic losses. In this paper, two operational models, TRAMS and ECMWF, which are commonly used by forecasters in South China, are selected to divide the torrential rain during dragon-boat precipitation into front-zone torrential rain and warm-sector torrential rain, and are verified and evaluated, in order to understand the characteristics of the two models’ biases for the front-zone torrential rain and warm-sector torrential rain under the background of the extreme dragon-boat precipitation. Compared with the traditional point-to-point method, the MODE method can effectively avoid the phenomenon of high false alarm ratio caused by precipitation position deviation in the model. Further analysis of the number, position, precipitation area and intensity of torrential rain objects based on MODE method shows that the high-resolution model TRAMS has better ability to identify and match torrential rain objects than the global model ECMWF. The position prediction of torrential rain by TRAMS mostly has a eastward bias, while ECMWF has a northward bias. The deviations in precipitation position are closely related to the differences in the forecast bias of the two models for low-level southwesterly flow. The area prediction of the front-zone torrential rain by TRAMS is close to the observation, while the forecast area of warm-sector torrential rain is large. The forecast areas of ECMWF for both front-zone torrential rain and warm-sector torrential rain are small. The prediction of torrential rain intensity and extreme value by TRAMS is closer to the observation than that by ECMWF, but it still underestimates the extreme precipitation. This study can provide new experience for forecasters to understand the prediction biases of different operational models for dragon-boat precipitation process. It also has reference value for model developers to further carry out research on error source diagnosis and technical improvement of TRAMS.
Available online: February 12, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.011602
Abstract:
Based on the observation data of FY-4A Advanced Geosynchronous Radiation Imager(AGRI) and ground observation data during 2018—2020, the distribution characteristics of satellite products in different severe convective weather,which contained short-term heavy precipitation,lightning and hail,were studied by using statistical methods such as normal distribution test and correlation analysis. The results show that: (1) The difference of convection in severe convective weather leads to the different distribution characteristics of FY-4A satellite products. During short-term heavy precipitation, the cloud top temperature and black body temperature are mainly concentrated between 235~275K, and different cloud shapes lead to significant differences in temperature ranges, while during lightning and hail, the main range is located between 225~250K, which are lower than short-term heavy precipitation. More than 50% of short-term heavy precipitation, 75% of lightning, and more than 90% of hail occurred at altitudes above 5000m (500hPa); The radii of cloud droplets in different convective weather are obviously different. Short-term heavy precipitation, lightning and hail correspond to relatively large cloud droplets, small cloud droplets and large cloud droplets respectively; When the liquid water content in clouds exceeds 500 g?m-2, short-term heavy precipitation is prone to occur, while lightning ranges from 300 to 350 g?m-2 but hail ranges from 400 to 600 g?m-2; The deepest folding depth of the moderate intensity troposphere is conducive to the occurrence and maintenance of heavy precipitation and lightning, while hail requires deeper folding depth. (2) Except that the cloud top temperature and the cloud top height in the lightning hail series show normal distribution or quasi-normal distribution characteristics, other products do not conform to normal distribution. (3) There are three, three and five categories of FY-4A products significantly related to short-time heavy precipitation(CTT,TBB and TZD), lightning(CTT,TBB and TZD) and hail(CTT,CTH,TBB,LWP and TZD), respectively, which can be paid more attention to in monitoring and early warning.
Based on the observation data of FY-4A Advanced Geosynchronous Radiation Imager(AGRI) and ground observation data during 2018—2020, the distribution characteristics of satellite products in different severe convective weather,which contained short-term heavy precipitation,lightning and hail,were studied by using statistical methods such as normal distribution test and correlation analysis. The results show that: (1) The difference of convection in severe convective weather leads to the different distribution characteristics of FY-4A satellite products. During short-term heavy precipitation, the cloud top temperature and black body temperature are mainly concentrated between 235~275K, and different cloud shapes lead to significant differences in temperature ranges, while during lightning and hail, the main range is located between 225~250K, which are lower than short-term heavy precipitation. More than 50% of short-term heavy precipitation, 75% of lightning, and more than 90% of hail occurred at altitudes above 5000m (500hPa); The radii of cloud droplets in different convective weather are obviously different. Short-term heavy precipitation, lightning and hail correspond to relatively large cloud droplets, small cloud droplets and large cloud droplets respectively; When the liquid water content in clouds exceeds 500 g?m-2, short-term heavy precipitation is prone to occur, while lightning ranges from 300 to 350 g?m-2 but hail ranges from 400 to 600 g?m-2; The deepest folding depth of the moderate intensity troposphere is conducive to the occurrence and maintenance of heavy precipitation and lightning, while hail requires deeper folding depth. (2) Except that the cloud top temperature and the cloud top height in the lightning hail series show normal distribution or quasi-normal distribution characteristics, other products do not conform to normal distribution. (3) There are three, three and five categories of FY-4A products significantly related to short-time heavy precipitation(CTT,TBB and TZD), lightning(CTT,TBB and TZD) and hail(CTT,CTH,TBB,LWP and TZD), respectively, which can be paid more attention to in monitoring and early warning.
Available online: February 10, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.012001
Abstract:
To improve the accuracy of precipitation nowcasting, this paper proposes an adversarial neural network model named CastNet that combines deep neural networks. This model utilizes the Recurrent Neural Network (RNN) to capture the spatio-temporal features of radar echo data, employs the Adversarial Neural Network (GAN) to simulate the generation and dissipation changes of cloud clusters, and then integrates the optical flow constraint into the neural network to guide the model training, which accelerates the learning process of the neural network and enhances the spatio-temporal consistency of the model, effectively solving the problem of forecast ambiguity and significantly improving the accuracy of precipitation intensity and location. Tests were conducted on 9 major precipitation processes in Guangxi and its surrounding areas (104.41° - 112.08°E, 20.9° - 26.49°N) from May to October 2023. The results show that under various precipitation intensities (≥0.1, ≥2, ≥7, ≥15, ≥25 and≥40 mmh?1), the average TS scores of SWAN 2.0 are 0.458, 0.27, 0.085, 0.034, 0.014 and 0.003 respectively; the average TS scores of SWAN 3.0 are 0.452, 0.402, 0.225, 0.129, 0.085 and 0.048 respectively; and the average TS scores of the CastNet model are 0.439, 0.397, 0.225, 0.139, 0.104 and 0.073 respectively. Its scores are higher than those of SWAN 2.0 and SWAN 3.0 under high-intensity precipitation of ≥7 mmh?1 and above. In addition, as the forecast lead time extends, the relative advantage of CastNet becomes more obvious.
To improve the accuracy of precipitation nowcasting, this paper proposes an adversarial neural network model named CastNet that combines deep neural networks. This model utilizes the Recurrent Neural Network (RNN) to capture the spatio-temporal features of radar echo data, employs the Adversarial Neural Network (GAN) to simulate the generation and dissipation changes of cloud clusters, and then integrates the optical flow constraint into the neural network to guide the model training, which accelerates the learning process of the neural network and enhances the spatio-temporal consistency of the model, effectively solving the problem of forecast ambiguity and significantly improving the accuracy of precipitation intensity and location. Tests were conducted on 9 major precipitation processes in Guangxi and its surrounding areas (104.41° - 112.08°E, 20.9° - 26.49°N) from May to October 2023. The results show that under various precipitation intensities (≥0.1, ≥2, ≥7, ≥15, ≥25 and≥40 mmh?1), the average TS scores of SWAN 2.0 are 0.458, 0.27, 0.085, 0.034, 0.014 and 0.003 respectively; the average TS scores of SWAN 3.0 are 0.452, 0.402, 0.225, 0.129, 0.085 and 0.048 respectively; and the average TS scores of the CastNet model are 0.439, 0.397, 0.225, 0.139, 0.104 and 0.073 respectively. Its scores are higher than those of SWAN 2.0 and SWAN 3.0 under high-intensity precipitation of ≥7 mmh?1 and above. In addition, as the forecast lead time extends, the relative advantage of CastNet becomes more obvious.
Available online: February 08, 2025 , DOI: 10.7519/j.issn.1000-0526.2024.111501
Abstract:
A comprehensive meteorological risk early warning method for mountain torrent disasters is proposed using the fuzzy evaluation method in this paper. The method is based on the dynamic critical rainfall for mountain torrent early warning that considers soil water content saturation, then a correspondence between meteorological risk warning levels and fuzzy scores for mountain torrent disasters is established based on the fuzzy evaluation method. The weight algorithms are constructed respectively using the weighted average method, the coefficient of determination, and the relative error of peak flow. With this method , together with the fuzzy scores for meteorological risk warning calculated by using the precipitation forecasts from CMA-MESO, CMA-SH9, CMA-BJ and intelligent grid forecasting，the comprehensive meteorological risk level is determined. The results show that the hit rate of the comprehensive risk early warning results based on the fuzzy evaluation method is comparable to that of the CMA-BJ and higher than other models, the miss rate and false alarm rate are also comparable to those of the CMA-BJ and lower than other models,the TS scores are all higher than those of other models, through the application and verification of the mountain torrent disaster in Hengshui of Anyang River from 17 to 22 July 2021. This method can extend the lead time of mountain torrent prediction and improve the accuracy of early warning. This research result provides a new approach for the meteorological risk warning service of small watershed mountain torrent disasters in China.
A comprehensive meteorological risk early warning method for mountain torrent disasters is proposed using the fuzzy evaluation method in this paper. The method is based on the dynamic critical rainfall for mountain torrent early warning that considers soil water content saturation, then a correspondence between meteorological risk warning levels and fuzzy scores for mountain torrent disasters is established based on the fuzzy evaluation method. The weight algorithms are constructed respectively using the weighted average method, the coefficient of determination, and the relative error of peak flow. With this method , together with the fuzzy scores for meteorological risk warning calculated by using the precipitation forecasts from CMA-MESO, CMA-SH9, CMA-BJ and intelligent grid forecasting，the comprehensive meteorological risk level is determined. The results show that the hit rate of the comprehensive risk early warning results based on the fuzzy evaluation method is comparable to that of the CMA-BJ and higher than other models, the miss rate and false alarm rate are also comparable to those of the CMA-BJ and lower than other models,the TS scores are all higher than those of other models, through the application and verification of the mountain torrent disaster in Hengshui of Anyang River from 17 to 22 July 2021. This method can extend the lead time of mountain torrent prediction and improve the accuracy of early warning. This research result provides a new approach for the meteorological risk warning service of small watershed mountain torrent disasters in China.
Available online: February 08, 2025 , DOI: 10.7519/j.issn.1000-0526.2024.122702
Abstract:
Based on the precipitation data from automatic weather stations and ERA5 reanalysis data, case seletion and classification of synoptic circulation are carried on for warm-sector heavy rainfall of the first rainy season in Huizhou from April to June 2003 to 2021. And a comparison is used to study the characteristics of mean synoptic circulation and environmental parameters between different types of warm-sector rainfall events. The results showed that there are a total of 47 warm-sector heavy rainfall events in Huizhou during the first rainy season. Accroding to synoptic circulation, the selected warm-sector rainfall events are divided into three types, i.e., shear line (the first type), shortwave trough low level jet (the second type), and the edge of subtropical high the entrance of low level jet(the third type). A further comparison of mean synoptic circulation between different types of warm-sector rainfall events show that Huizhou is under the control of the west wind flow and the southwest flow around the subtropical high at 500hPa, except for the second type of heavy rainfall. In low-level, there are double low-level jet(southwest low-level jet and boundary layer low-level jet) near Huizhou both in the second and third type of heavy rainfall, while in the first type of heavy rain, boundary layer low-level jet just occurred in the south of the Pearl River Estuary at 925hPa. Finally, the analysis of environmental parameters indicate that in terms of average, the first type of heavy rainfall is superior to other types of heavy rainfall in vertical wind shear; the second type of heavy rainfall is superior to other types of heavy rainfall in the depression of dew point at 850hPa、atmospheric precipitable water、convective available potential energy and K index; the third type of heavy rainfall is superior to other types of heavy rainfall in the maximum southerly wind speed below 850hPa.
Based on the precipitation data from automatic weather stations and ERA5 reanalysis data, case seletion and classification of synoptic circulation are carried on for warm-sector heavy rainfall of the first rainy season in Huizhou from April to June 2003 to 2021. And a comparison is used to study the characteristics of mean synoptic circulation and environmental parameters between different types of warm-sector rainfall events. The results showed that there are a total of 47 warm-sector heavy rainfall events in Huizhou during the first rainy season. Accroding to synoptic circulation, the selected warm-sector rainfall events are divided into three types, i.e., shear line (the first type), shortwave trough low level jet (the second type), and the edge of subtropical high the entrance of low level jet(the third type). A further comparison of mean synoptic circulation between different types of warm-sector rainfall events show that Huizhou is under the control of the west wind flow and the southwest flow around the subtropical high at 500hPa, except for the second type of heavy rainfall. In low-level, there are double low-level jet(southwest low-level jet and boundary layer low-level jet) near Huizhou both in the second and third type of heavy rainfall, while in the first type of heavy rain, boundary layer low-level jet just occurred in the south of the Pearl River Estuary at 925hPa. Finally, the analysis of environmental parameters indicate that in terms of average, the first type of heavy rainfall is superior to other types of heavy rainfall in vertical wind shear; the second type of heavy rainfall is superior to other types of heavy rainfall in the depression of dew point at 850hPa、atmospheric precipitable water、convective available potential energy and K index; the third type of heavy rainfall is superior to other types of heavy rainfall in the maximum southerly wind speed below 850hPa.
Available online: January 21, 2025 , DOI: 10.7519/j.issn.1000-0526.2024.122701
Abstract:
Using the China Meteorological Administration"s best track data from 1949 to 2023, real-time operational forecast data on typhoon tracks and intensity for 2023 form National Meteorological Centre of CMA, and other sources of observations and models including the ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF), the main characteristics of typhoon activity in the Northwest Pacific in 2023 are analyzed. The results show that in 2023, the number of typhoon formations and landfalls were both relatively low, while the extreme intensity of typhoons and landfall intensities were stronger. The genesis region of typhoons shifted eastward, with fewer typhoons in the South China Sea and fewer summer landfall typhoons. Typhoon landfalls were concentrated in specific areas, with typhoons penetrating further inland and causing widespread and severe damage. Although the Central Meteorological Observatory"s 24-hour typhoon track forecast error in 2023 reached a historic low, the track forecast errors within five days were generally higher than that of the Japan Meteorological Agency (JMA) and the U.S. Joint Typhoon Warning Center (JTWC). However, the intensity forecast errors for typhoons within 1-5 days lead time increased compared to last five years" levels, though still better than JMA and worse than JTWC. The challenges in typhoon forecasting in 2023 included the inland penetration and prolonged duration of Typhoon Doksuri, resulting in extreme precipitation in North China, the remnant vortex of Typhoon Haikui triggering extreme precipitation in South China, and the two sharp turns in the track of Typhoon Khanun. The causes of these challenging forecast events are analyzed in this study.
Using the China Meteorological Administration"s best track data from 1949 to 2023, real-time operational forecast data on typhoon tracks and intensity for 2023 form National Meteorological Centre of CMA, and other sources of observations and models including the ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF), the main characteristics of typhoon activity in the Northwest Pacific in 2023 are analyzed. The results show that in 2023, the number of typhoon formations and landfalls were both relatively low, while the extreme intensity of typhoons and landfall intensities were stronger. The genesis region of typhoons shifted eastward, with fewer typhoons in the South China Sea and fewer summer landfall typhoons. Typhoon landfalls were concentrated in specific areas, with typhoons penetrating further inland and causing widespread and severe damage. Although the Central Meteorological Observatory"s 24-hour typhoon track forecast error in 2023 reached a historic low, the track forecast errors within five days were generally higher than that of the Japan Meteorological Agency (JMA) and the U.S. Joint Typhoon Warning Center (JTWC). However, the intensity forecast errors for typhoons within 1-5 days lead time increased compared to last five years" levels, though still better than JMA and worse than JTWC. The challenges in typhoon forecasting in 2023 included the inland penetration and prolonged duration of Typhoon Doksuri, resulting in extreme precipitation in North China, the remnant vortex of Typhoon Haikui triggering extreme precipitation in South China, and the two sharp turns in the track of Typhoon Khanun. The causes of these challenging forecast events are analyzed in this study.
Available online: January 17, 2025 , DOI: 10.7519/j.issn.1000-0526.2024.121902
Abstract:
Based on the 2019～2023 grid rainfall observation and multi-model forecasts in Zhejiang Province during the flood season from May to October, the accuracy evaluation of the areal rainfall for 32 large-sized reservoir basins in Zhejiang Province by multi-model Objective Consensus Forecasting (OCF) are evaluated based on various methods, which are further compared with those of the European Centre for Medium-Range Weather Forecasts (ECF). The results demonstrate that the forecast accuracy of areal rainfall by OCF model is related to the catchment area of reservoir, the location of reservoir and the weather process that causes precipitation. On the whole, the forecast accuracy of areal rainfall by OCF model for Type I large-sized reservoirs is higher than that for Type II. The forecast error of OCF model mainly comes from the missing alarm. By reducing the missing alarm rate, the forecast accuracy of areal rainfall by OCF model for Type II large-sized reservoirs located in Central and East Zhejiang can be significantly improved, especially for the areal rainfall over 15 mm, which has obvious advantages over ECF model. Although the prediction accuracy of OCF model decreases gradually with the extension of forecast time, it has better effect than ECF model in the forecast of the areal rainfall over 6 mm. For different heavy precipitation processes in Zhejiang Province, OCF model has higher forecasting ability and better performance than ECF model for the reservoir basins mainly affected by Meiyu (typhoon) during Meiyu period (Typhoon period). The prediction accuracy of OCF model improves with the approach of forecast time during both Meiyu and Typhoon periods. However, owing to the influence of the predictability of typhoon tracks, the latter fluctuates dramatically and has obvious advantages over ECF model in most forecast time of 24～120 h. The above results can provide the necessary reference for the hydrometeorological service.
Based on the 2019～2023 grid rainfall observation and multi-model forecasts in Zhejiang Province during the flood season from May to October, the accuracy evaluation of the areal rainfall for 32 large-sized reservoir basins in Zhejiang Province by multi-model Objective Consensus Forecasting (OCF) are evaluated based on various methods, which are further compared with those of the European Centre for Medium-Range Weather Forecasts (ECF). The results demonstrate that the forecast accuracy of areal rainfall by OCF model is related to the catchment area of reservoir, the location of reservoir and the weather process that causes precipitation. On the whole, the forecast accuracy of areal rainfall by OCF model for Type I large-sized reservoirs is higher than that for Type II. The forecast error of OCF model mainly comes from the missing alarm. By reducing the missing alarm rate, the forecast accuracy of areal rainfall by OCF model for Type II large-sized reservoirs located in Central and East Zhejiang can be significantly improved, especially for the areal rainfall over 15 mm, which has obvious advantages over ECF model. Although the prediction accuracy of OCF model decreases gradually with the extension of forecast time, it has better effect than ECF model in the forecast of the areal rainfall over 6 mm. For different heavy precipitation processes in Zhejiang Province, OCF model has higher forecasting ability and better performance than ECF model for the reservoir basins mainly affected by Meiyu (typhoon) during Meiyu period (Typhoon period). The prediction accuracy of OCF model improves with the approach of forecast time during both Meiyu and Typhoon periods. However, owing to the influence of the predictability of typhoon tracks, the latter fluctuates dramatically and has obvious advantages over ECF model in most forecast time of 24～120 h. The above results can provide the necessary reference for the hydrometeorological service.
Available online: January 17, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.010801
Abstract:
Liquid Water Content (LWC), Median Volume Diameter (MVD), Outside Air Temperature (OAT) and other meteorological conditions are important meteorological factors affecting the intensity of aircraft icing, and are also the basic condition for measuring and evaluating whether the aircraft natural icing test flight meets the airworthiness standard. The meteorological conditions of a domestic large passenger aircraft"s natural icing test flight on January 22, 2022 were analyzed using multi-source meteorological data. The results show that the high-altitude weather background of this natural icing forensic test flight is a latitudinal fluctuating airflow, and the near-surface layer cooperates with the cold air inversion, forcing the southwest warm and humid airflow in the middle and lower layers of the troposphere to lift northward, and forming a wide range of non-precipitation layered cloud system. The height of the cloud top in the test area developed from 3.0 km to 4.6 km, and an inversion layer existed in 1.3-3.5 km, with the lowest temperature at the cloud top of -14 ℃, no precipitation in the cloud, and the radar basic reflectivity＜15 dBz. The ambient temperature of the two times of penetrating the cloud and the standby flight in the cloud for 45 min hovering flights was -10～-7 ℃, the relative humidity＞80%, and the scattering of water vapor flux＜-2.7×10-7 g/(s?hPa?cm2), providing ideal temperature and water vapor conditions for the natural icing test flights, and a weak updraft of -0.2 Pa?s-1 in the middle and upper part of the cloud layer, which contributes to the growth of the supercooled cloud droplets. The DMT sounding data show that the supercooled cloud is inhomogeneous both vertically and horizontally, and that supercooled cloud droplets predominate inside the cloud, and the average LWC value is 0.23-0.27 g?m-3, and the mean value of MVD is 15.82-15.93 μm. There are natural aircraft ice meteorological conditions in winter under the influence of the "inversion + inversion trough" weather system, which is conducive to carrying out aircraft natural icing forensic tests in Shaanxi.
Liquid Water Content (LWC), Median Volume Diameter (MVD), Outside Air Temperature (OAT) and other meteorological conditions are important meteorological factors affecting the intensity of aircraft icing, and are also the basic condition for measuring and evaluating whether the aircraft natural icing test flight meets the airworthiness standard. The meteorological conditions of a domestic large passenger aircraft"s natural icing test flight on January 22, 2022 were analyzed using multi-source meteorological data. The results show that the high-altitude weather background of this natural icing forensic test flight is a latitudinal fluctuating airflow, and the near-surface layer cooperates with the cold air inversion, forcing the southwest warm and humid airflow in the middle and lower layers of the troposphere to lift northward, and forming a wide range of non-precipitation layered cloud system. The height of the cloud top in the test area developed from 3.0 km to 4.6 km, and an inversion layer existed in 1.3-3.5 km, with the lowest temperature at the cloud top of -14 ℃, no precipitation in the cloud, and the radar basic reflectivity＜15 dBz. The ambient temperature of the two times of penetrating the cloud and the standby flight in the cloud for 45 min hovering flights was -10～-7 ℃, the relative humidity＞80%, and the scattering of water vapor flux＜-2.7×10-7 g/(s?hPa?cm2), providing ideal temperature and water vapor conditions for the natural icing test flights, and a weak updraft of -0.2 Pa?s-1 in the middle and upper part of the cloud layer, which contributes to the growth of the supercooled cloud droplets. The DMT sounding data show that the supercooled cloud is inhomogeneous both vertically and horizontally, and that supercooled cloud droplets predominate inside the cloud, and the average LWC value is 0.23-0.27 g?m-3, and the mean value of MVD is 15.82-15.93 μm. There are natural aircraft ice meteorological conditions in winter under the influence of the "inversion + inversion trough" weather system, which is conducive to carrying out aircraft natural icing forensic tests in Shaanxi.
Available online: January 17, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.011601
Abstract:
Two persistent extreme rainstorms occurred in Sichuan Basin on August 10-13 and 14-18 in 2020 resulting in secondary disasters,casualties,and huge economic losses.To deeply understand the development mechanism of extreme rainstorms and its disaster causing mechanism using various observations and ERA5 reanalysis data,the precipitation characteristics of these two rainstorms, as well as the development,evolution,and trigger mechanism of MCSs in the heaviest precipitation stage of these two rainstorms were analyzed. The results showed that the two processes occurred under the Ω type circulation background with “two troughs and one ridge”? in the middle and high latitudes.Besides, they were typical rainstorms accompanied by “east-high-pressure and west-low-pressure” in the basin.And both had precipitation over 250 mm/day(or 100 mm/h). The hourly rainfall of the “8.10-13” rainstorm exceeded the historical extremes,while that of the “8.14-18”rainstorm was equivalent to the historical statistical value. The strongest precipitation stage of the “8.10-13” rainstorm was a warm-sector rainstorm,which was caused by a MCC occurrence-development-maturation-weakening process. The radar echo areas greater than or equal to 40 dBZ in this rainstorm were wide and long-lasting.And the echo centroid was low and the intensity was more than 50 dBZ. The heaviest precipitation phase of the “8.14-18” rainstorm was a mixed precipitation induced by a two α-MCS occurrence-development-merger-weakening process.The radar echo areas greater than or equal to 40dBZ were narrow and short-lived.The echo centroid was low and the intensity reached 50 dBZ.Convection in the "8.10-13" rainfall was produced by horn mouth terrain flow, windward slop uplift and high temperature gradient zone，and sustained with strong warm advection at low level，weak cold advection at high level at the same time.The “8.14-18” rainstorm convection was triggered by the convergence of the lower troposphere cold,warm currents and the left convergence of the low-altitude jet stream in the warm zone.The shear formed by the intersection of the cold and warm currents caused the precipitation lasting.
Two persistent extreme rainstorms occurred in Sichuan Basin on August 10-13 and 14-18 in 2020 resulting in secondary disasters,casualties,and huge economic losses.To deeply understand the development mechanism of extreme rainstorms and its disaster causing mechanism using various observations and ERA5 reanalysis data,the precipitation characteristics of these two rainstorms, as well as the development,evolution,and trigger mechanism of MCSs in the heaviest precipitation stage of these two rainstorms were analyzed. The results showed that the two processes occurred under the Ω type circulation background with “two troughs and one ridge”? in the middle and high latitudes.Besides, they were typical rainstorms accompanied by “east-high-pressure and west-low-pressure” in the basin.And both had precipitation over 250 mm/day(or 100 mm/h). The hourly rainfall of the “8.10-13” rainstorm exceeded the historical extremes,while that of the “8.14-18”rainstorm was equivalent to the historical statistical value. The strongest precipitation stage of the “8.10-13” rainstorm was a warm-sector rainstorm,which was caused by a MCC occurrence-development-maturation-weakening process. The radar echo areas greater than or equal to 40 dBZ in this rainstorm were wide and long-lasting.And the echo centroid was low and the intensity was more than 50 dBZ. The heaviest precipitation phase of the “8.14-18” rainstorm was a mixed precipitation induced by a two α-MCS occurrence-development-merger-weakening process.The radar echo areas greater than or equal to 40dBZ were narrow and short-lived.The echo centroid was low and the intensity reached 50 dBZ.Convection in the "8.10-13" rainfall was produced by horn mouth terrain flow, windward slop uplift and high temperature gradient zone，and sustained with strong warm advection at low level，weak cold advection at high level at the same time.The “8.14-18” rainstorm convection was triggered by the convergence of the lower troposphere cold,warm currents and the left convergence of the low-altitude jet stream in the warm zone.The shear formed by the intersection of the cold and warm currents caused the precipitation lasting.
Available online: January 16, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.011502
Abstract:
To provide reference for the prediction of major floods in the upper reaches of the Han River during the autumn flood season, based on NCEP/NCAR reanalysis data and conventional meteorological and hydrological observation data, the water and rainfall characteristics, rainfall response relationships, abnormal large-scale circulation patterns, and causes of flood precipitation of the Han River during the autumn flood season since the 21st century were studied. The research results showed that: ①The flood process in the Han River Basin during the autumn flood season in the 21st century gradually increased. The heavy rainfall center during the autumn flood season was mainly located in the southern and western parts of the upper reaches of the Han River. The frequency of precipitation on the southern bank was much higher than that on the northern bank, and in mountainous areas it was greater than in rivers and basins. The upstream was greater than the downstream; There were three centers: the area around Micang Mountain and Daba Mountain on the south side of the Han River Basin, the riverside valley above Ankang Reservoir, and the Danjiang River section at the southern foot of the outer mountain and the southwest slope of Funiu Mountain. ②The flood peak generally presents in three forms: single peak, double peak, and multi peak. It was feasible to judge single peak, multi peak, or bimodal floods based on precipitation intensity, time, and frequency. There was generally a pre discharge time of about 1-2 days from the occurrence of the strongest precipitation during the process period to the formation of floods.③The abnormally high precipitation during the autumn flood season in the upper reaches of the Han River was related to weather factors such as the 500hPa mid high latitude circulation pattern, the western Pacific subtropical high pressure, the southerly pressure high pressure and subtropical westerly jet, the plateau trough, the blocking high pressure and cold air activity, and water vapor transport. Under abnormal circulation conditions, when continuous rainy weather was combined with higher initial inflow of Danjiangkou Reservoir, flood peaks were likely to form in the upper reaches of the Han River.
To provide reference for the prediction of major floods in the upper reaches of the Han River during the autumn flood season, based on NCEP/NCAR reanalysis data and conventional meteorological and hydrological observation data, the water and rainfall characteristics, rainfall response relationships, abnormal large-scale circulation patterns, and causes of flood precipitation of the Han River during the autumn flood season since the 21st century were studied. The research results showed that: ①The flood process in the Han River Basin during the autumn flood season in the 21st century gradually increased. The heavy rainfall center during the autumn flood season was mainly located in the southern and western parts of the upper reaches of the Han River. The frequency of precipitation on the southern bank was much higher than that on the northern bank, and in mountainous areas it was greater than in rivers and basins. The upstream was greater than the downstream; There were three centers: the area around Micang Mountain and Daba Mountain on the south side of the Han River Basin, the riverside valley above Ankang Reservoir, and the Danjiang River section at the southern foot of the outer mountain and the southwest slope of Funiu Mountain. ②The flood peak generally presents in three forms: single peak, double peak, and multi peak. It was feasible to judge single peak, multi peak, or bimodal floods based on precipitation intensity, time, and frequency. There was generally a pre discharge time of about 1-2 days from the occurrence of the strongest precipitation during the process period to the formation of floods.③The abnormally high precipitation during the autumn flood season in the upper reaches of the Han River was related to weather factors such as the 500hPa mid high latitude circulation pattern, the western Pacific subtropical high pressure, the southerly pressure high pressure and subtropical westerly jet, the plateau trough, the blocking high pressure and cold air activity, and water vapor transport. Under abnormal circulation conditions, when continuous rainy weather was combined with higher initial inflow of Danjiangkou Reservoir, flood peaks were likely to form in the upper reaches of the Han River.
Available online: January 14, 2025 , DOI: 10.7519/j.issn.1000-0526.2024.121901
Abstract:
Eight different cloud microphysics schemes in the WRF model are used to simulate the precipitation process of a squall line that occurred in Hainan Island on 22 April 2020, and the effects of different cloud microphysics schemes on the simulation of the Hainan Island squall line are compared and analyzed. The results show that different cloud microphysics schemes have significant differences in the simulation of surface precipitation, radar composite reflectivity and thermal dynamic field. Among them, the intensity of precipitation area and center simulated by Thompson scheme are most close to the actual observations, and the radar composite reflectivity simulated by WSM6 scheme at the time of maximum precipitation is similar to the actual observations in intensity, range and form. In the thermal dynamic field, the characteristics of squall line such as surface cold pool, low-level vertical wind shear and cold pool outflow are simulated by each scheme,and the precipitation center is corresponded to the strong updraft region. The divergence structure of low-level convergence and high-level divergence is conducive to the occurrence of strong convection and the formation of precipitation, but the intensity and distribution are different. According to the cloud microphysical characteristics, the liquid phase particles are mainly distributed below 5 km, and the ice phase particales are above 6 km. The simulation results of cloud water show the weakest response to the selection of cloud microphysics schemes, while the distributions of snow and graupel show the high sensitivity.
Eight different cloud microphysics schemes in the WRF model are used to simulate the precipitation process of a squall line that occurred in Hainan Island on 22 April 2020, and the effects of different cloud microphysics schemes on the simulation of the Hainan Island squall line are compared and analyzed. The results show that different cloud microphysics schemes have significant differences in the simulation of surface precipitation, radar composite reflectivity and thermal dynamic field. Among them, the intensity of precipitation area and center simulated by Thompson scheme are most close to the actual observations, and the radar composite reflectivity simulated by WSM6 scheme at the time of maximum precipitation is similar to the actual observations in intensity, range and form. In the thermal dynamic field, the characteristics of squall line such as surface cold pool, low-level vertical wind shear and cold pool outflow are simulated by each scheme,and the precipitation center is corresponded to the strong updraft region. The divergence structure of low-level convergence and high-level divergence is conducive to the occurrence of strong convection and the formation of precipitation, but the intensity and distribution are different. According to the cloud microphysical characteristics, the liquid phase particles are mainly distributed below 5 km, and the ice phase particales are above 6 km. The simulation results of cloud water show the weakest response to the selection of cloud microphysics schemes, while the distributions of snow and graupel show the high sensitivity.
Available online: January 14, 2025 , DOI: 10.7519/j.issn.1000-0526.2024.111401
Abstract:
To address the issue of high-concealed abnormal wind directions in automatic weather station (AWS) data，this study establish an abnormal wind direction identification method based on the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) clustering algorithm. Historical wind direction data from 16 weather events affecting Guangzhou between 2016 and 2022, including cold waves, cold air masses, and typhoons, as well as real-time wind direction data from AWSs during the impact of Typhoon Sura (No. 2309), were used to detect abnormal wind directions. The analysis results reveal that the proportion of AWSs with suspicious wind directions in historical cases ranges from 0.46% to 5.56%, while the proportion of AWSs with erroneous wind directions ranges from 0.25% to 2.05%.During the real-time case of Typhoon Sura,the method identified 13 AWSs with significantly deviating wind directions from the dominant ground wind direction, primarily due to wind direction sensor malfunctions and environmental impacts on AWS observations. Compared to the traditional method, the accuracy of wind direction error identification has improved by 20.32%.The new method provides a novel approach for the quality control of historical wind direction data from AWSs and offers an effective reference for the operational monitoring and on-site verification of AWS equipment.
To address the issue of high-concealed abnormal wind directions in automatic weather station (AWS) data，this study establish an abnormal wind direction identification method based on the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) clustering algorithm. Historical wind direction data from 16 weather events affecting Guangzhou between 2016 and 2022, including cold waves, cold air masses, and typhoons, as well as real-time wind direction data from AWSs during the impact of Typhoon Sura (No. 2309), were used to detect abnormal wind directions. The analysis results reveal that the proportion of AWSs with suspicious wind directions in historical cases ranges from 0.46% to 5.56%, while the proportion of AWSs with erroneous wind directions ranges from 0.25% to 2.05%.During the real-time case of Typhoon Sura,the method identified 13 AWSs with significantly deviating wind directions from the dominant ground wind direction, primarily due to wind direction sensor malfunctions and environmental impacts on AWS observations. Compared to the traditional method, the accuracy of wind direction error identification has improved by 20.32%.The new method provides a novel approach for the quality control of historical wind direction data from AWSs and offers an effective reference for the operational monitoring and on-site verification of AWS equipment.
Available online: January 13, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.011301
Abstract:
Based on the prediction results of Beijing Climate Center-climate prediction system version 3-subseasonal to seasonal version 2 (BCC-CPSv3-S2Sv2), various evaluation and test methods are used to test the prediction effect of the model in the flood season of the Yangtze River Basin, and to evaluate the prediction skills of daily/ten-day precipitation in the flood season of the Yangtze River Basin. The model error characteristics are studied, and the available forecasting time-scale of model precipitation is analyzed. The results show that the model has systematically overestimated the precipitation in flood season in the Yangtze River Basin as a whole, and the prediction skill in the middle and lower reaches of the Yangtze River is higher than that in the upper reaches of the Yangtze River, and the prediction effect in August is significantly better than that in June and July; the prediction skill of the model is improved with the approaching of the starting time. The effective prediction time of the model for the daily quantitative prediction of the flood season in the Yangtze River Basin is about ten days, and the qualitative prediction of the precipitation anomaly in the flood season is similar: the prediction skill of ten days in advance is the highest, and the prediction of twenty to thirty days in advance also has some reference value. In addition, the model"s prediction skill under the less rain scenario is better than that under the more rain scenario, but its prediction ability for extreme climate events is still relatively weak.
Based on the prediction results of Beijing Climate Center-climate prediction system version 3-subseasonal to seasonal version 2 (BCC-CPSv3-S2Sv2), various evaluation and test methods are used to test the prediction effect of the model in the flood season of the Yangtze River Basin, and to evaluate the prediction skills of daily/ten-day precipitation in the flood season of the Yangtze River Basin. The model error characteristics are studied, and the available forecasting time-scale of model precipitation is analyzed. The results show that the model has systematically overestimated the precipitation in flood season in the Yangtze River Basin as a whole, and the prediction skill in the middle and lower reaches of the Yangtze River is higher than that in the upper reaches of the Yangtze River, and the prediction effect in August is significantly better than that in June and July; the prediction skill of the model is improved with the approaching of the starting time. The effective prediction time of the model for the daily quantitative prediction of the flood season in the Yangtze River Basin is about ten days, and the qualitative prediction of the precipitation anomaly in the flood season is similar: the prediction skill of ten days in advance is the highest, and the prediction of twenty to thirty days in advance also has some reference value. In addition, the model"s prediction skill under the less rain scenario is better than that under the more rain scenario, but its prediction ability for extreme climate events is still relatively weak.
Available online: January 06, 2025 , DOI: 10.7519/j.issn.1000-0526.2024.123001
Abstract:
This study analyzes the damaging winds event (maximum wind speed of 31.5 m·s-1) happened at Tianjin Airport on August 4, 2013, focusing on the synoptic background, storm structure and the formation mechanism of severe winds. The results show that this case occurred in the unstable region behind the upper-level trough, which has a prominent midtropospheric dry layer while moisture is mainly concentrated at low levels below 925 hPa. The convective available potential energy is greater than 3000 J·kg-1, in addition to the strong 0-6 km vertical wind shear and the large lapse rate in the boundary layer, is conducive to the formation of severe winds. The damaging winds are caused by a northwest-southeast propagating squall line. A wind speed spike and pressure surge is observed during the gust front passage, prior to the arrival of the convective line. And the maximum wind gust happens when the squall line arrives, resulting mainly from the downburst of a rapid developing multicell storm. A strong rear inflow jet and the decline of it, together with the latent cooling, hydrometeor loading and the convergence of mid-level airflow are responsible for the formation of strong downdrafts and severe surface winds.
This study analyzes the damaging winds event (maximum wind speed of 31.5 m·s-1) happened at Tianjin Airport on August 4, 2013, focusing on the synoptic background, storm structure and the formation mechanism of severe winds. The results show that this case occurred in the unstable region behind the upper-level trough, which has a prominent midtropospheric dry layer while moisture is mainly concentrated at low levels below 925 hPa. The convective available potential energy is greater than 3000 J·kg-1, in addition to the strong 0-6 km vertical wind shear and the large lapse rate in the boundary layer, is conducive to the formation of severe winds. The damaging winds are caused by a northwest-southeast propagating squall line. A wind speed spike and pressure surge is observed during the gust front passage, prior to the arrival of the convective line. And the maximum wind gust happens when the squall line arrives, resulting mainly from the downburst of a rapid developing multicell storm. A strong rear inflow jet and the decline of it, together with the latent cooling, hydrometeor loading and the convergence of mid-level airflow are responsible for the formation of strong downdrafts and severe surface winds.
Available online: January 03, 2025 , DOI: 10.7519/j.issn.1000-0526.2025.010201
Abstract:
According to the specific image feature that the bird echo shows obvious ring shape on the Weather Radar reflectivity product, an improved algorithm based on a lightweight convolutional neural network You Only Look Once Version5（YOLOv5） and multi-object tracking based on Deep learning based Simple Online and Realtime Tracking（DeepSort） is proposed to identify ,the?training?and?test?datasets?are?constructed?fromradar?volumetric?scanning?echo?intensity data?obtained?from?the?Yingkou Weather?Radar?from?2020?to?2023, track the bird echo respectively. Firstly, Shuffle Attention（SA）, a lightweight attention mechanism, is introduced into YOLOv5 algorithm to improve the accuracy and effectiveness of the overall model detection. Secondly, in DeepSort algorithm, the original cross merge ratio Intersection over Union（IOU） matching mechanism is replaced by an improved the loss function of object detection Distance-Intersection over Union（DIOU） matching mechanism. DIoU introduces the distance between the center points of the boundary box on the basis of calculating the overlap degree of the boundary box, so as to provide more accurate positioning. The number of identification （ID） error matching and ID switching caused by partial occlusion overlap is reduced. The experimental results show that the optimized YOLOv5 algorithm improves the accuracy by 2.6%, the recall rate by 1%, and the average accuracy of threshold values greater than 0.5 by 1.2%. The improved DeepSort algorithm reduces the number of ID switches by 2 times, multi target tracking accuracy Multi-Object Tracking Accuracy（MOTA） increases by 4.5%, the improved lightweight of the initial model, and the overall detection performance is significantly improved, meeting the actual demand for bird echo recognition and tracking.
According to the specific image feature that the bird echo shows obvious ring shape on the Weather Radar reflectivity product, an improved algorithm based on a lightweight convolutional neural network You Only Look Once Version5（YOLOv5） and multi-object tracking based on Deep learning based Simple Online and Realtime Tracking（DeepSort） is proposed to identify ,the?training?and?test?datasets?are?constructed?fromradar?volumetric?scanning?echo?intensity data?obtained?from?the?Yingkou Weather?Radar?from?2020?to?2023, track the bird echo respectively. Firstly, Shuffle Attention（SA）, a lightweight attention mechanism, is introduced into YOLOv5 algorithm to improve the accuracy and effectiveness of the overall model detection. Secondly, in DeepSort algorithm, the original cross merge ratio Intersection over Union（IOU） matching mechanism is replaced by an improved the loss function of object detection Distance-Intersection over Union（DIOU） matching mechanism. DIoU introduces the distance between the center points of the boundary box on the basis of calculating the overlap degree of the boundary box, so as to provide more accurate positioning. The number of identification （ID） error matching and ID switching caused by partial occlusion overlap is reduced. The experimental results show that the optimized YOLOv5 algorithm improves the accuracy by 2.6%, the recall rate by 1%, and the average accuracy of threshold values greater than 0.5 by 1.2%. The improved DeepSort algorithm reduces the number of ID switches by 2 times, multi target tracking accuracy Multi-Object Tracking Accuracy（MOTA） increases by 4.5%, the improved lightweight of the initial model, and the overall detection performance is significantly improved, meeting the actual demand for bird echo recognition and tracking.
Available online: December 26, 2024 , DOI: 10.7519/j.issn.1000-0526.2024.111801
Abstract:
Doppler spectral is the Ka-band cloud radar original data. Based on the consistency difference between cloud-precipitation signal and the ‘ghost echo’ along with other noise signals in different Doppler spectral modes, this study used the difference between short-pulse and long-pulse modes to determine the cloud signal boundary for the first time. The ‘ghost echo’ was removed and the cloud signal boundary was used to calculated the noise level, forming a new denoising method. In addition, the sensitivity of cloud signal boundary changing with the difference threshold T was analyzed. Based on the small particle tracer method, the left cloud signal boundary after denoising was used to calculate the vertical air velocity. Two rainfall (snow) cases in Beijing were analyzed and compared with the in-situ aircraft observation results of the vertical air velocity. It was verified that the new denoising method can effectively remove the ‘ghost echo’. Although a certain percentage deviation existed between the average vertical air velocity obtained by cloud radar and aircraft. The direction and magnitude corresponded well in general. This method and the retrieved results were reasonable.
Doppler spectral is the Ka-band cloud radar original data. Based on the consistency difference between cloud-precipitation signal and the ‘ghost echo’ along with other noise signals in different Doppler spectral modes, this study used the difference between short-pulse and long-pulse modes to determine the cloud signal boundary for the first time. The ‘ghost echo’ was removed and the cloud signal boundary was used to calculated the noise level, forming a new denoising method. In addition, the sensitivity of cloud signal boundary changing with the difference threshold T was analyzed. Based on the small particle tracer method, the left cloud signal boundary after denoising was used to calculate the vertical air velocity. Two rainfall (snow) cases in Beijing were analyzed and compared with the in-situ aircraft observation results of the vertical air velocity. It was verified that the new denoising method can effectively remove the ‘ghost echo’. Although a certain percentage deviation existed between the average vertical air velocity obtained by cloud radar and aircraft. The direction and magnitude corresponded well in general. This method and the retrieved results were reasonable.
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: 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: 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.
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2012,38(12):1482-1491, DOI: 10.7519/j.issn.1000-0526.2012.12.005
Abstract:
By using the conventional meteorological data, Doppler radar data and NCEP/NCAR reanalysis data, the characteristics of Doppler radar’s reflectivity, environmental condition and trigger mechanism of the heavy rain are analyzed and compared between two abrupt heavy rain processes occurring in Sichuan Basin on 3 July (7.3) and 23 July (7.23) 2011. The results show that: the “7.3” heavy rain happened under a typical circulation background, and moisture transporting to the heavy rain area from the South China Sea was smoothly, thus the heavy rainfall maintained so long, but the “7.23” heavy rain occurred behind the upper cold vortex, and convective unstable energy was abundant and vertical wind shear was strong, thus this heavy rain process happened with hail and thunderstorm weather accompanied, its radar reflectivity was 5 dBz stronger than “7.3” case and had the characteristics of severe storms such as the low level weak reflectivity and the upper echo overhang. As a whole, the non equilibrium force is contributed to the occurrence of heavy rain and it is the excited mechanism of the two heavy rainfalls, and the change of the divergence evolvement is consistent with the strength and the position of the heavy rain which would happen 6 hours later．
By using the conventional meteorological data, Doppler radar data and NCEP/NCAR reanalysis data, the characteristics of Doppler radar’s reflectivity, environmental condition and trigger mechanism of the heavy rain are analyzed and compared between two abrupt heavy rain processes occurring in Sichuan Basin on 3 July (7.3) and 23 July (7.23) 2011. The results show that: the “7.3” heavy rain happened under a typical circulation background, and moisture transporting to the heavy rain area from the South China Sea was smoothly, thus the heavy rainfall maintained so long, but the “7.23” heavy rain occurred behind the upper cold vortex, and convective unstable energy was abundant and vertical wind shear was strong, thus this heavy rain process happened with hail and thunderstorm weather accompanied, its radar reflectivity was 5 dBz stronger than “7.3” case and had the characteristics of severe storms such as the low level weak reflectivity and the upper echo overhang. As a whole, the non equilibrium force is contributed to the occurrence of heavy rain and it is the excited mechanism of the two heavy rainfalls, and the change of the divergence evolvement is consistent with the strength and the position of the heavy rain which would happen 6 hours later．
2017,43(7):769-780, DOI: 10.7519/j.issn.1000-0526.2017.07.001
Abstract:
The spatial distributions of severe convective wind (SCW) and nonsevere thunderstorms (NT) over South China, occurring between 08:00 BT and 20:00 BT during spring and summer in 2010-2014, were analyzed by using the observational data from China Meteorological Administration. And then, their environmental characteristics were compared between SCW and NT in spring and summer. It was found that SCW in summer is more frequently than that in spring and that NT in summer is about 3.6 times the counts of NT in spring. SCW events mainly concentrate in the western Guangdong to the Pearl River Delta Region. Compared to NT, SCW is generally associated with stronger baroclinity, instability and stronger dynamic forcing. The precipitable water and averaged relative humidity between 700-500 hPa of SCW tend to be higher than those of NT in spring, while the opposite is the case for the pattern in summer. In conclusion, it is obvious that the dynamic forcing for SCW in spring is much better than these in summer, while the thermal condition is more significant in summer.
The spatial distributions of severe convective wind (SCW) and nonsevere thunderstorms (NT) over South China, occurring between 08:00 BT and 20:00 BT during spring and summer in 2010-2014, were analyzed by using the observational data from China Meteorological Administration. And then, their environmental characteristics were compared between SCW and NT in spring and summer. It was found that SCW in summer is more frequently than that in spring and that NT in summer is about 3.6 times the counts of NT in spring. SCW events mainly concentrate in the western Guangdong to the Pearl River Delta Region. Compared to NT, SCW is generally associated with stronger baroclinity, instability and stronger dynamic forcing. The precipitable water and averaged relative humidity between 700-500 hPa of SCW tend to be higher than those of NT in spring, while the opposite is the case for the pattern in summer. In conclusion, it is obvious that the dynamic forcing for SCW in spring is much better than these in summer, while the thermal condition is more significant in summer.
2010,36(3):9-18, DOI: 10.7519/j.issn.1000-0526.2010.3.002
Abstract:
Potential vorticity (PV) is one of the important concepts in advanced synoptic and dynamic meteorology. This paper is a brief introduction to the theory of potential vorticity, including the concept of PV, the conservation and invertibility of PV, PV thinking, moist PV (MPV), and the application of PV theory.
Potential vorticity (PV) is one of the important concepts in advanced synoptic and dynamic meteorology. This paper is a brief introduction to the theory of potential vorticity, including the concept of PV, the conservation and invertibility of PV, PV thinking, moist PV (MPV), and the application of PV theory.
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.
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.
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.
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.
2012,38(1):1-16, DOI: 10.7519/j.issn.1000-0526.2012.01.001
Abstract:
In this paper, the modulation of atmospheric MJO on typhoon generation over the northwestern Pacific and its mechanism are first studied by using the MJO index. The results show that the MJO plays an important modulation role in typhoon generation over the northwestern Pacific: The proportion of typhoon number is 21 between active period and inactive period; During the MJO active period, the proportion of typhoon number is also 2:1 between phases 5-6 and phases 2-3 of MJO. The composite analyses of atmospheric circulation show that there are different circulation patterns over the northwestern Pacific in different phases of the MJO, which will affect the typhoon generation. In phases 5-6 (2-3), the dynamic factor and convective heating patterns over western Pacific are favorable (unfavorable) for typhoon generation. Then， the comparing analyses of the 30-60 day low frequency kinetic energy in lower and higher levels of the troposphere show that the atmospheric intraseasonal oscillation over the northwestern Pacific has a clear impact on the typhoon generation. There is an evident positive (negative) anomaly area of 30-60 day low frequency kinetic energy in the more (less) typhoon years over the northwestern Pacific east of the Philippines, which means that strong (weak) atmospheric intraseasonal oscillation (ISO) over the northwestern Pacific is favorable (unfavorable) for typhoon generation. The analyses of 200 hPa velocity potential show that there is a clear divergence (convergence) pattern over the northwestern Pacific in the more (less) typhoon years, which is favorable (unfavorable) for typhoon generation. The modulation of the intraseasonal oscillation on the typhoon tracks over the northwestern Pacific is studied by observational data analyses. We classified the main classes of typhoon tracks into 5 types as straight west moving typhoons (I), northwest moving typhoons (II), recurving to Korea/west of Japan typhoons (III), landing on Japan typhoons (IV) and recurving to the east of Japan typhoons (V). Then the composite analyses of atmospheric low-frequency wind fields at 850, 500 and 200 hPa, corresponding to the typhoon forming date, for every typhoon track are completed. The analysis results of relationships between the low-frequency (ISO) wind fields and typhoon tracks have indicated that the typhoon tracks will be affected by wind pattern of the ISO. The low frequency positive vorticity belt (the maximum value line of cyclonic vorticity) associated with low-frequency cyclone (LFC) at 850 hPa is so closely related to the typhoon track, that the maximum value line (belt) of low frequency cyclonic vorticity can be an important factor to predicate the typhoon tracks over the northwestern Pacific. And the typhoon tracks will be also affected by the ISO circulation pattern at 200 hPa, particularly the strong low frequency wind associated with low frequency anticyclone (LFAC).
In this paper, the modulation of atmospheric MJO on typhoon generation over the northwestern Pacific and its mechanism are first studied by using the MJO index. The results show that the MJO plays an important modulation role in typhoon generation over the northwestern Pacific: The proportion of typhoon number is 21 between active period and inactive period; During the MJO active period, the proportion of typhoon number is also 2:1 between phases 5-6 and phases 2-3 of MJO. The composite analyses of atmospheric circulation show that there are different circulation patterns over the northwestern Pacific in different phases of the MJO, which will affect the typhoon generation. In phases 5-6 (2-3), the dynamic factor and convective heating patterns over western Pacific are favorable (unfavorable) for typhoon generation. Then， the comparing analyses of the 30-60 day low frequency kinetic energy in lower and higher levels of the troposphere show that the atmospheric intraseasonal oscillation over the northwestern Pacific has a clear impact on the typhoon generation. There is an evident positive (negative) anomaly area of 30-60 day low frequency kinetic energy in the more (less) typhoon years over the northwestern Pacific east of the Philippines, which means that strong (weak) atmospheric intraseasonal oscillation (ISO) over the northwestern Pacific is favorable (unfavorable) for typhoon generation. The analyses of 200 hPa velocity potential show that there is a clear divergence (convergence) pattern over the northwestern Pacific in the more (less) typhoon years, which is favorable (unfavorable) for typhoon generation. The modulation of the intraseasonal oscillation on the typhoon tracks over the northwestern Pacific is studied by observational data analyses. We classified the main classes of typhoon tracks into 5 types as straight west moving typhoons (I), northwest moving typhoons (II), recurving to Korea/west of Japan typhoons (III), landing on Japan typhoons (IV) and recurving to the east of Japan typhoons (V). Then the composite analyses of atmospheric low-frequency wind fields at 850, 500 and 200 hPa, corresponding to the typhoon forming date, for every typhoon track are completed. The analysis results of relationships between the low-frequency (ISO) wind fields and typhoon tracks have indicated that the typhoon tracks will be affected by wind pattern of the ISO. The low frequency positive vorticity belt (the maximum value line of cyclonic vorticity) associated with low-frequency cyclone (LFC) at 850 hPa is so closely related to the typhoon track, that the maximum value line (belt) of low frequency cyclonic vorticity can be an important factor to predicate the typhoon tracks over the northwestern Pacific. And the typhoon tracks will be also affected by the ISO circulation pattern at 200 hPa, particularly the strong low frequency wind associated with low frequency anticyclone (LFAC).
2011,37(10):1262-1269, DOI: 10.7519/j.issn.1000-0526.2011.10.009
Abstract:
Based on the daily precipitation data at 110 observational stations during 1961-2008 in South China， the climatic characteristics and variation of torrential rain days， rainstorm intensity and contribution which is in annual， the first and second flood seasons in South China were studied by using statistical and diagnostic methods， such as linear regression analysis， Mann Kendall test， wavelet analysis and the computation of trend coefficients. The results have shown that the annual mean torrential rain days have a decreasing trend from coastal regions to inland in South China in recent 48 years， the highest center is in Dongxing of Guangxi （14.9 d）， and the lowest center is in Longlin of Guangxi （3.2 d）. About 72% of the total torrential rain days occurred in the flood seasons with about 45% in the first season and 27% in the second season. The mean torrential rain days have increased faintly in annual， the first and second flood seasons in South China， but it is not obvious. There are the characteristics of interannual and interdecadal changes. The mean rainstorm intensity has increased faintly in annual and in the first flood season in South China. However, since 2005 it has become obviously. The mean rainstorm intensity has declined in the second flood season， but it is not obvious. The annual mean rainstorm contribution to the total rainfall has increased obviously， but the mean contribution is not obvious in the first and second flood seasons. The wavelet analysis has shown that the changes of torrential rain days， intensity and contribution which is in annual， the first and second flood seasons in South China have two significant periods of 2-3 a and 3-4 a.
Based on the daily precipitation data at 110 observational stations during 1961-2008 in South China， the climatic characteristics and variation of torrential rain days， rainstorm intensity and contribution which is in annual， the first and second flood seasons in South China were studied by using statistical and diagnostic methods， such as linear regression analysis， Mann Kendall test， wavelet analysis and the computation of trend coefficients. The results have shown that the annual mean torrential rain days have a decreasing trend from coastal regions to inland in South China in recent 48 years， the highest center is in Dongxing of Guangxi （14.9 d）， and the lowest center is in Longlin of Guangxi （3.2 d）. About 72% of the total torrential rain days occurred in the flood seasons with about 45% in the first season and 27% in the second season. The mean torrential rain days have increased faintly in annual， the first and second flood seasons in South China， but it is not obvious. There are the characteristics of interannual and interdecadal changes. The mean rainstorm intensity has increased faintly in annual and in the first flood season in South China. However, since 2005 it has become obviously. The mean rainstorm intensity has declined in the second flood season， but it is not obvious. The annual mean rainstorm contribution to the total rainfall has increased obviously， but the mean contribution is not obvious in the first and second flood seasons. The wavelet analysis has shown that the changes of torrential rain days， intensity and contribution which is in annual， the first and second flood seasons in South China have two significant periods of 2-3 a and 3-4 a.
2014,40(4):400-411, DOI: 10.7519/j.issn.1000-0526.2014.04.002
Abstract:
Based on the synoptic environment analysis of about 100 severe convection cases in China since 2000 and the reference of related literatures, from the perspectives of the three essential conditions for the development of severe convection, namely the thermal instability, lift and moisture, five basic synoptic situation configurations of severe convection in China are proposed and expounded. They are cold advection forcing category, warm advection forcing category, baroclinic frontogenesis category, quasi barotropic category and elevated thunderstorm category. The typical characteristics of the upper cold advection forcing category is that the mid upper strong cold advection above 500 hPa strengthens and reaches the boundary warm convergence zone. The warm advection forcing category is characterized by trough with special structure moving over low level strong warm and moist advection. The deep convection produced by the mid lower layer convergence of cold and warm air features the baroclinic frontogenesis category. The quasi barotropic category mostly occurs at the northern and the southern edges or the interior of summer subtropical high and the area with weak baroclinicity, where the dynamic forcing and the surface inhomogeneous local heating play major roles. The features of elevated thunderstorms are the southwest jet in 700-500 hPa lifted by boundary cold wedge and the instable energy is from above 700 hPa. The classification based on the difference of the formation mechanisms can grasp accurately the synoptic characteristics, the situation configurations, the dynamic and thermal properties and the key points in analyzing short term potential forecast, providing more technical support to further enhance the level of weather prediction.
Based on the synoptic environment analysis of about 100 severe convection cases in China since 2000 and the reference of related literatures, from the perspectives of the three essential conditions for the development of severe convection, namely the thermal instability, lift and moisture, five basic synoptic situation configurations of severe convection in China are proposed and expounded. They are cold advection forcing category, warm advection forcing category, baroclinic frontogenesis category, quasi barotropic category and elevated thunderstorm category. The typical characteristics of the upper cold advection forcing category is that the mid upper strong cold advection above 500 hPa strengthens and reaches the boundary warm convergence zone. The warm advection forcing category is characterized by trough with special structure moving over low level strong warm and moist advection. The deep convection produced by the mid lower layer convergence of cold and warm air features the baroclinic frontogenesis category. The quasi barotropic category mostly occurs at the northern and the southern edges or the interior of summer subtropical high and the area with weak baroclinicity, where the dynamic forcing and the surface inhomogeneous local heating play major roles. The features of elevated thunderstorms are the southwest jet in 700-500 hPa lifted by boundary cold wedge and the instable energy is from above 700 hPa. The classification based on the difference of the formation mechanisms can grasp accurately the synoptic characteristics, the situation configurations, the dynamic and thermal properties and the key points in analyzing short term potential forecast, providing more technical support to further enhance the level of weather prediction.
2014,40(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.
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.
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.
2015,41(2):212-218, DOI: 10.7519/j.issn.1000-0526.2015.02.009
Abstract:
From 1 May to 8 June 2013 CMA Meteorological Observation Centre conducted an experiment of cloud height observations by using cloud radar (35 GHz), whose observation data are the echo power value and temporal resolution is 1 min and a ceilometer whose observation data are the back scattering intens data with 1 min temporal resolution. The result of analyzing the data observed from the 39 d experiment indicates that: (1) the data acquisition ratio of cloud radar is 26% larger than that of ceilometer; (2) the ratio is 51% in fog haze weather; (3) relatively, precipitation has more significant effect on cloud base height measured by laser ceilometer than that by cloud radar; (4) height of cloud base measured by cloud radar is almost consistent with the height by ceilometer because their average deviation is less than 300 m.
From 1 May to 8 June 2013 CMA Meteorological Observation Centre conducted an experiment of cloud height observations by using cloud radar (35 GHz), whose observation data are the echo power value and temporal resolution is 1 min and a ceilometer whose observation data are the back scattering intens data with 1 min temporal resolution. The result of analyzing the data observed from the 39 d experiment indicates that: (1) the data acquisition ratio of cloud radar is 26% larger than that of ceilometer; (2) the ratio is 51% in fog haze weather; (3) relatively, precipitation has more significant effect on cloud base height measured by laser ceilometer than that by cloud radar; (4) height of cloud base measured by cloud radar is almost consistent with the height by ceilometer because their average deviation is less than 300 m.
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.
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