Based on meteorological data of Zhumadian City in the past 56 years, the damage of flood-causing rainstorm to towns in Zhumadian City as well as its cataclysm form, influencing system, cataclysm characteristics and ac...Based on meteorological data of Zhumadian City in the past 56 years, the damage of flood-causing rainstorm to towns in Zhumadian City as well as its cataclysm form, influencing system, cataclysm characteristics and action mechanism were analyzed to discuss the characteristics and rules of damage caused by flood-causing rainstorm. Meanwhile, countermeasures against flood-causing rainstorm cataclysm in Zhumadian City were proposed to provide scientific references for early warning and monitoring of flood-causing rainstorm as well as flood control and disaster mitigation.展开更多
The diabatic heating is calculated, using the thermodynamic equation in isobaric coordinates, of a heavy rainstorm that developed over Jeddah, Saudi Arabia on 25 November 2009. Throughout the period of study, the hori...The diabatic heating is calculated, using the thermodynamic equation in isobaric coordinates, of a heavy rainstorm that developed over Jeddah, Saudi Arabia on 25 November 2009. Throughout the period of study, the horizontal heat advection is the dominant term and the vertical advection term is opposed by the adiabatic one. The contribution of the local temperature term to the change in diabatic heating is relatively very minimal. The presence of the Red Sea and its adjacent mountains suggest that the diabatic heating in the lower atmosphere on that rainy day is primarily due to the latent heat released by convection. The dynamics of the studied case is also investigated in terms of isobaric Potential Vorticity (PV). The results show that the heating region coincides with the location of the low-level PV anomaly. Ertel’s Potential Vorticity (EPV) generation estimates imply that condensation supplies a large enough source of moisture to account for the presence of the low-level EPV anomaly. The low-level diabatic heating-produced PV assisted in amplifying the surface thermal wave early in the rainstorm development and in the upper-level wave during the later stages of the system’s growth.展开更多
[ ObjEtive] The research aimed to analyze ＂96.8＂ heavy rainstorm process causing flood disaster in Handan. [ Method] Based on ac- tual situation data, satellite cloud data and NCEP reanalysis data in the first dekad...[ ObjEtive] The research aimed to analyze ＂96.8＂ heavy rainstorm process causing flood disaster in Handan. [ Method] Based on ac- tual situation data, satellite cloud data and NCEP reanalysis data in the first dekad of August in 1996, ＂96.8＂ heavy rainstorm process causing flood disaster in Handan was analyzed to understand occurrence reason of the flood disaster. [ Result] Two meso-scale convective cloud clusters which developed and went north in turn caused ＂96.8＂ heavy rainstorm in Handan. Typhoon and inverted trough were main weather systems induced flood disaster in Handan. In going north process of the low-level jet, due to blocking of the subtropical high, water vapor and energy accumulated in Handan, providing material basis for formation of the heavy rainstorm. Development and eastward movement of the short-wave trough at middle lati- tude and continuous invasion of the reflux weak cold air at the low layer were direct reason for triggering generation and development of the convec- tive cloud cluster, and further causing continuous rainstorm. Wet layer over the rainstorm zone was deep and thick. Meridional distribution of the wet zone was wider than latitudinal distribution. South China Sea and Bay of Bengal were water vapor sources for the rainstorm zone. In the whole rain- storm period, it was convergence at low layer and divergence at high layer in the rainstorm zone. It was positive vorticity at low layer and negative vorticity at high layer. Precipitation intensity changed as convergence and divergence. Rainstorm zone had strong ascending motion. As strengthe- ning and uplifting of the ascending motion strong center, strong precipitation also strengthened. Rainstorm center was near the biggest vertical ve- locity center. Strong precipitation changed as vertical ascending motion. [ Conclmion] The research provided scientific basis for disaster prevention and reduction and decision-making service.展开更多
[Objective] The research aimed to carry out numerical simulation on impact of land-surface process in a Meiyu front rainstorm.[Method] Based on the meso-scale atmospheric non-hydrostatic model GRAPES-Meso which couple...[Objective] The research aimed to carry out numerical simulation on impact of land-surface process in a Meiyu front rainstorm.[Method] Based on the meso-scale atmospheric non-hydrostatic model GRAPES-Meso which coupled with NOAH land-surface module,a Meiyu front rainstorm in Jianghuai basin during 6-8 July,2005 was simulated.Via sensitivity tests with and without land-surface process,the impact of land-surface process on Meiyu front rainstorm was studied.[Result] GRAPES-Meso which coupled with NOAH land-surface process could simulate daily variation characteristics of Meiyu front precipitation and atmospheric low-level southwest jet.The land-surface process could improve the simulations of precipitation initiation,intensity and distribution.The improvement of precipitation initiation simulation was especially obvious,which solved spin-up problem of model to some extent.When the land-atmosphere interaction wasn’t considered,the precipitation initiation of model was very slow.The intensity evolution of simulated precipitation was different from actual situation.Moreover,it couldn’t simulate daily variation characteristics of precipitation and southwest jet.[Conclusion] The land-surface process had important impact on Meiyu process in Jianghuai basin.展开更多
By using the daily precipitation data from 1961 to 2005 in North China region,the temporal and spatial distribution characteristics of rainstorm process occurrence and the rainstorm intensity during the crops growth p...By using the daily precipitation data from 1961 to 2005 in North China region,the temporal and spatial distribution characteristics of rainstorm process occurrence and the rainstorm intensity during the crops growth period were studied.The results showed that the rainstorm intensity and the rainstorm process during the crops growth period in North China region both had the obvious annual fluctuations and era variation characteristics.Although the rainstorm and heavy rainstorm occurred in North China region every year,the annual variations were great,and the variation coefficients respectively reached 36.9% and 53.1%.The torrential rain occurred once in every 4-5 years,and the rainstorm process occurred once in every 11 years.Although the torrential rain and rainstorm process occurred in fewer years,their annual fluctuations were more obvious.The peak value zones of rainstorm intensity which was greater and the rainstorm process which occurred frequently were in the 1960s.After 1999,the rainstorm intensity and the rainstorm process were in low value zone of historical stage from 1961 to 2005.Moreover,the 1970s-1990s was between high value and low value,and the rainstorms in different intensities which weren't synchronous happened in the period.In addition,the spatial distribution of annual average rainstorm days presented the tendency which increased obviously from northwest to southeast in Northern China,and the variation coefficient of rainstorm days presented the tendency which increased gradually from southeast to northwest.Generally,the more the annual average rainstorm days are,the smaller the variation coefficient is,and vice versa.The statistics results also showed that precipitation in North China had obvious positive correlation relationship with the rainstorm days.展开更多
为给秋汛期汉江上游大洪水天气预报提供参考,基于NCEP/NCAR再分析资料及常规气象水文实况观测资料,研究了2000年以来汉江上游秋汛期大洪水的水情、雨情特征、大尺度环流形势特征以及致洪暴雨成因,结果表明:进入21世纪秋汛期汉江流域洪...为给秋汛期汉江上游大洪水天气预报提供参考,基于NCEP/NCAR再分析资料及常规气象水文实况观测资料,研究了2000年以来汉江上游秋汛期大洪水的水情、雨情特征、大尺度环流形势特征以及致洪暴雨成因,结果表明:进入21世纪秋汛期汉江流域洪水过程逐渐增多。致洪暴雨中心主要位于汉江上游南部和西部,即汉江流域南侧的米仓山、大巴山一带,安康水库以上的沿江河谷一带,及外方山南麓和伏牛山西南坡处的丹江河段。洪水峰值呈现单峰、双峰和多峰型。单峰型洪水过程持续时间最短,多峰型持续时间最长。从过程最大降水开始至洪峰出现,平均历时43 h,当起始入库流量超过4500 m 3·s^(-1)以上时,洪峰形成所需时长将大为缩短。从大尺度环流特征来看,汉江上游秋汛期降水偏多与欧亚中高纬阻塞系统强盛,西太洋副热带高压偏强、偏西,南亚高压及副热带西风急流偏北密切相关,高空辐散场大值区对应汉江上游所在区域,低层至高层的垂直运动增强,有利于致洪暴雨的发生。汉江上游秋汛期大洪水年源自阿拉伯海经由印度半岛和南海南部向北输送的水汽异常增多、西太平洋向西输送的水汽异常增多,为致洪暴雨的发生提供了异常充足的水汽供给。展开更多
On May 20 th 2007, a brief but severe downpour rainstorm occurred in the coastal areas of Maoming and Yangjiang with rainfall of 115 mm per hour. Data from NCEP/NCAR reanalysis with 1°×1° resolution, Do...On May 20 th 2007, a brief but severe downpour rainstorm occurred in the coastal areas of Maoming and Yangjiang with rainfall of 115 mm per hour. Data from NCEP/NCAR reanalysis with 1°×1° resolution, Doppler weather radar, conventional surface observations, high-altitude radiosonde and wind profiler radar were used to analyze characteristics and contributions of synoptic scale and mesoscale systems during this torrential rainstorm. The results showed that:(1) the storm was caused by a quasi-linear mesoscale convective system(MCS) and the slow-movement of this system was the primary trigger of the torrential downpour;(2) water vapor was abundant, nearly saturated and in steady state throughout the atmosphere before the storm; intrusion of the weak dry and cold air in the middle level and a striking "dry above and wet below " structure had increased the atmospheric instability;(3) low-level southwesterly airflow from a low pressure(trough) at the Beibu Gulf provided abundant water vapor at the onset of the rainstorm; a deep dry layer was formed by dry and cold air behind the high-level trough, which facilitated latent heat release;upper-level divergence and low-level convergence circulations also provided vertical uplift for warm and moist air at the lower level;(4) Topography only played a minor role as the MCS developed and strengthened over relatively flat coastal terrain. Low level density flow induced by convection triggered new convective cell generation at the leading edge of the convective system, thereby playing a key role in the change of temperature gradient at lower layers, and resulting in strengthening atmospheric instability.展开更多
[Objective] The research aimed to analyze a regional rainstorm weather process in north-central Henan Province. [Method] Based on the conventional meteorological observation data and the rainfall data of Henan Meteoro...[Objective] The research aimed to analyze a regional rainstorm weather process in north-central Henan Province. [Method] Based on the conventional meteorological observation data and the rainfall data of Henan Meteorological Station, the diagnostic analysis of atmospheric thermodynamics and dynamics on a rainstorm weather process in north-central Henan Province on July 19, 2010 was carried out. The characteristics of physical quantity field and the evolution of weather situation in north-central Henan Province when the rainstorm happened were studied. [Result] Western Pacific subtropical high strengthened to extend westward. The dynamic uplifting of low vortex at the middle and low layers, the strong water vapor transportation of southwest low-level jet caused the regional rainstorm weather process in north-central Henan Province. The diagnostic results of physical quantity showed that the deep, thick wet layer and the sustained water vapor convergence provided the abundant water vapor for rainstorm generation. The positive vorticity advection center developed and spread from northwest to southeast, which was favorable for the development of vertical movement. The structure maintenance of positive vorticity at the middle and low layers, negative vorticity at the middle and high levels provided the power condition for the regional rainstorm generation. The pumping effect of convergence at the middle and low layers, divergence at the high layer was favorable for the strengthening of vertical ascending motion at the low layer. The uplifting effect of dew point front at the middle and low layers triggered the release of unstable energy. The confrontation of warm and cold air was one of the important reasons for the regional rainstorm. TBB characteristic analysis showed that TBB was from -60 to -50 ℃ in north-central Henan Province in the whole strong precipitation time, and the moving speed was equivalent to that of southwest vortex. The low-value belt of TBB corresponded with the rainstorm occurrence zone in Henan, and the minimum-value center of TBB was basically consistent with the strongest center of precipitation. [Conclusion] The research provided the scientific basis for the short-term forecast of rainstorm.展开更多
[Objective] The aim was to study one rainstorm process being affected by two weather system. [Method] Influenced by high trough and Mongolia cold front, high latitude trough and subtropical high shear, rainstorm occur...[Objective] The aim was to study one rainstorm process being affected by two weather system. [Method] Influenced by high trough and Mongolia cold front, high latitude trough and subtropical high shear, rainstorm occurred in Jinzhou from October 19 to 22 in 2010. In order to make the analysis clear, there were two precipitation stages. Considering precipitation, weather situation, satellite image and numerical forecast, the rainstorm process was discussed. [Result] There were two raining stages during this precipitation. The first stage was affected by high altitude trough and ground Mongolia cold front, and the last stage was influenced by high altitude trough and subtropical high shear;the high latitude air, low latitude shear,low air torrent,subtropical high and their mutual coupling effect were the main influencing system and cause for this rainstorm. Satellite image suggested that there was convective cloud developing,weakening, disappearing and regenerating around the convective cloud of water vapor passage, showing distinct train operation state. The strengthening and weakening cloud image fitted the real precipitation. Numerical forecast precisely predicted the upper air and ground situation of the generation of rainstorm, especially the report of the east-retreating and south-falling trend of subtropical high;European center forecast fitted reality. There was certain error in predicting T639. Precipitation forecast was fine. [Conclusion] The study provided basis for the meteorological service work in future.展开更多
[Objective] The aim was to comparatively analyze two local heavy rainstroms in northwestern Shandong Province, China. [Method] Based on the observation data from automatic weather station, sounding data and NCEP reana...[Objective] The aim was to comparatively analyze two local heavy rainstroms in northwestern Shandong Province, China. [Method] Based on the observation data from automatic weather station, sounding data and NCEP reanalysis data, two local heavy rainstorms at night on July 18 and August 9 in 2010 in northwestern Shandong was comparatively analyzed from the aspects of circulation situation, influence system and physical field, and the internal structure and possible formation mechanism of local heavy rain in Shandong were discussed further. [Result] The two rainstorms occurred in the forepart of southwest air in front of 500 hPa trough, and there was stronger atmospheric baroclinicity in the front zone near 850 hPa. The two rainstorms were affected by southwest warm and humid airflow at low level and shear line at 850 hPa; rainstorm often appeared in intensive area behind θse high-energy tongue, and rainstorm area corresponded with the area with high vertical speed well. From the differences, during the first rainstorm, there was obvious southwest low level jet and shear line at 700 hPa, and the area with high precipitation was located in the south of warm shear line at 700 hPa; during the latter rainstorm, there was no obvious southwest low level jet and shear line, and the area with high precipitation was located in the region between two high pressures. [Conclusion] The study could provide valuable thinking for the forecast of this kind of rainstorm in the future.展开更多
[Objective] A heavy rainstorm in Jincheng in August in 2010 was expounded. [Method] By dint of the conventional meteorological data, and automatic weather station data, and Doppler radar data, one severe torrential ra...[Objective] A heavy rainstorm in Jincheng in August in 2010 was expounded. [Method] By dint of the conventional meteorological data, and automatic weather station data, and Doppler radar data, one severe torrential rainstorm was analyzed from the aspect of circulation background, physical quantity field, satellite cloud image, and radar echo, etc. [Result] The rainstorm was in the circulation field of low-west-east-obstruction, and was formed under the middle and low layer shear line and low air torrent situation. The low layer shear and convergence of wind favorable to the lift of unsteady air around Jincheng. The intrusion of cold air in the low layer of convective layer and above the ground trigered such convective weather. The torrent of the low air in the southwest sent abundant water vapor to the rainstorm area. The high temperature and the moisture accumulated much unsteady energy for the generation of rainstorm. The main precipitation system of this process was the singular of convective echo which was stimulated by the ground mesoscale shear line. Under the guidance of southwest airstream of the low and middle air, the convective echo singular formed train effect by moving towards Jincheng and formed large rainstorm. Doppler radar data suggested that the characteristics of the generation, development and movement of this mesoscale rainstorm system. The strong precipitation center was in the large value area of the gradient in the back of the TBB center. [Conclusion] The study provided references for the forecast and pre-warning of temporary rainstorm of such kind.展开更多
An extraordinary rainstorm that occurred in Beijing on 21 July 2012 was simulated using the Weather Research and Forecasting model. The results showed that:(1) The two precipitation phases were based on a combination ...An extraordinary rainstorm that occurred in Beijing on 21 July 2012 was simulated using the Weather Research and Forecasting model. The results showed that:(1) The two precipitation phases were based on a combination of cold cloud processes and warm cloud processes. The accumulated conversion amount and conversion rate of microphysical processes in the warm-area phase were all much larger than those in the cold front phase.(2) 72.6% of rainwater was from the warm-area phase. Rainwater mainly came from the melting of graupel and the melting of snow, while the accretion of cloud water by rain ranked second.(3) The net heating rate with height appeared as an overall warming with two strong heating centers in the lower and middle layers of the troposphere and a minimum heating center around the melting layer. The net heating effect in the warm-area phase was stronger than that in the cold front phase.(4) Warm cloud processes contributed most to latent heat release, and the thermal effect of cold cloud processes on the storm in the cold front phase was enhanced compared to that in the warm-area phase.(5) The melting of graupel and snow contributed most to latent heat absorption, and the effect of the evaporation of rainwater was significantly reduced in the cold front phase.展开更多
文摘Based on meteorological data of Zhumadian City in the past 56 years, the damage of flood-causing rainstorm to towns in Zhumadian City as well as its cataclysm form, influencing system, cataclysm characteristics and action mechanism were analyzed to discuss the characteristics and rules of damage caused by flood-causing rainstorm. Meanwhile, countermeasures against flood-causing rainstorm cataclysm in Zhumadian City were proposed to provide scientific references for early warning and monitoring of flood-causing rainstorm as well as flood control and disaster mitigation.
文摘The diabatic heating is calculated, using the thermodynamic equation in isobaric coordinates, of a heavy rainstorm that developed over Jeddah, Saudi Arabia on 25 November 2009. Throughout the period of study, the horizontal heat advection is the dominant term and the vertical advection term is opposed by the adiabatic one. The contribution of the local temperature term to the change in diabatic heating is relatively very minimal. The presence of the Red Sea and its adjacent mountains suggest that the diabatic heating in the lower atmosphere on that rainy day is primarily due to the latent heat released by convection. The dynamics of the studied case is also investigated in terms of isobaric Potential Vorticity (PV). The results show that the heating region coincides with the location of the low-level PV anomaly. Ertel’s Potential Vorticity (EPV) generation estimates imply that condensation supplies a large enough source of moisture to account for the presence of the low-level EPV anomaly. The low-level diabatic heating-produced PV assisted in amplifying the surface thermal wave early in the rainstorm development and in the upper-level wave during the later stages of the system’s growth.
文摘[ ObjEtive] The research aimed to analyze ＂96.8＂ heavy rainstorm process causing flood disaster in Handan. [ Method] Based on ac- tual situation data, satellite cloud data and NCEP reanalysis data in the first dekad of August in 1996, ＂96.8＂ heavy rainstorm process causing flood disaster in Handan was analyzed to understand occurrence reason of the flood disaster. [ Result] Two meso-scale convective cloud clusters which developed and went north in turn caused ＂96.8＂ heavy rainstorm in Handan. Typhoon and inverted trough were main weather systems induced flood disaster in Handan. In going north process of the low-level jet, due to blocking of the subtropical high, water vapor and energy accumulated in Handan, providing material basis for formation of the heavy rainstorm. Development and eastward movement of the short-wave trough at middle lati- tude and continuous invasion of the reflux weak cold air at the low layer were direct reason for triggering generation and development of the convec- tive cloud cluster, and further causing continuous rainstorm. Wet layer over the rainstorm zone was deep and thick. Meridional distribution of the wet zone was wider than latitudinal distribution. South China Sea and Bay of Bengal were water vapor sources for the rainstorm zone. In the whole rain- storm period, it was convergence at low layer and divergence at high layer in the rainstorm zone. It was positive vorticity at low layer and negative vorticity at high layer. Precipitation intensity changed as convergence and divergence. Rainstorm zone had strong ascending motion. As strengthe- ning and uplifting of the ascending motion strong center, strong precipitation also strengthened. Rainstorm center was near the biggest vertical ve- locity center. Strong precipitation changed as vertical ascending motion. [ Conclmion] The research provided scientific basis for disaster prevention and reduction and decision-making service.
基金Supported by National Natural Science Fund Item,China (41005002,40875029)
文摘[Objective] The research aimed to carry out numerical simulation on impact of land-surface process in a Meiyu front rainstorm.[Method] Based on the meso-scale atmospheric non-hydrostatic model GRAPES-Meso which coupled with NOAH land-surface module,a Meiyu front rainstorm in Jianghuai basin during 6-8 July,2005 was simulated.Via sensitivity tests with and without land-surface process,the impact of land-surface process on Meiyu front rainstorm was studied.[Result] GRAPES-Meso which coupled with NOAH land-surface process could simulate daily variation characteristics of Meiyu front precipitation and atmospheric low-level southwest jet.The land-surface process could improve the simulations of precipitation initiation,intensity and distribution.The improvement of precipitation initiation simulation was especially obvious,which solved spin-up problem of model to some extent.When the land-atmosphere interaction wasn’t considered,the precipitation initiation of model was very slow.The intensity evolution of simulated precipitation was different from actual situation.Moreover,it couldn’t simulate daily variation characteristics of precipitation and southwest jet.[Conclusion] The land-surface process had important impact on Meiyu process in Jianghuai basin.
基金Supported by The National "The 11 th Five-Year" Science and Technology Support Project (2008BAK50B02)The Major Projects Cultivation Funds of Science and Technology Innovation Project in High Education Institutions of Education Ministry (708013 )The Science and Technology Commission Project in Beijing City (J08050503260803)
文摘By using the daily precipitation data from 1961 to 2005 in North China region,the temporal and spatial distribution characteristics of rainstorm process occurrence and the rainstorm intensity during the crops growth period were studied.The results showed that the rainstorm intensity and the rainstorm process during the crops growth period in North China region both had the obvious annual fluctuations and era variation characteristics.Although the rainstorm and heavy rainstorm occurred in North China region every year,the annual variations were great,and the variation coefficients respectively reached 36.9% and 53.1%.The torrential rain occurred once in every 4-5 years,and the rainstorm process occurred once in every 11 years.Although the torrential rain and rainstorm process occurred in fewer years,their annual fluctuations were more obvious.The peak value zones of rainstorm intensity which was greater and the rainstorm process which occurred frequently were in the 1960s.After 1999,the rainstorm intensity and the rainstorm process were in low value zone of historical stage from 1961 to 2005.Moreover,the 1970s-1990s was between high value and low value,and the rainstorms in different intensities which weren't synchronous happened in the period.In addition,the spatial distribution of annual average rainstorm days presented the tendency which increased obviously from northwest to southeast in Northern China,and the variation coefficient of rainstorm days presented the tendency which increased gradually from southeast to northwest.Generally,the more the annual average rainstorm days are,the smaller the variation coefficient is,and vice versa.The statistics results also showed that precipitation in North China had obvious positive correlation relationship with the rainstorm days.
文摘为给秋汛期汉江上游大洪水天气预报提供参考,基于NCEP/NCAR再分析资料及常规气象水文实况观测资料,研究了2000年以来汉江上游秋汛期大洪水的水情、雨情特征、大尺度环流形势特征以及致洪暴雨成因,结果表明:进入21世纪秋汛期汉江流域洪水过程逐渐增多。致洪暴雨中心主要位于汉江上游南部和西部,即汉江流域南侧的米仓山、大巴山一带,安康水库以上的沿江河谷一带,及外方山南麓和伏牛山西南坡处的丹江河段。洪水峰值呈现单峰、双峰和多峰型。单峰型洪水过程持续时间最短,多峰型持续时间最长。从过程最大降水开始至洪峰出现,平均历时43 h,当起始入库流量超过4500 m 3·s^(-1)以上时,洪峰形成所需时长将大为缩短。从大尺度环流特征来看,汉江上游秋汛期降水偏多与欧亚中高纬阻塞系统强盛,西太洋副热带高压偏强、偏西,南亚高压及副热带西风急流偏北密切相关,高空辐散场大值区对应汉江上游所在区域,低层至高层的垂直运动增强,有利于致洪暴雨的发生。汉江上游秋汛期大洪水年源自阿拉伯海经由印度半岛和南海南部向北输送的水汽异常增多、西太平洋向西输送的水汽异常增多,为致洪暴雨的发生提供了异常充足的水汽供给。
基金Guangdong Province Science and Technology Project(2017B020244002)National key basic research and development plan(973 plan)project"Typhoon fine structure multi-source data analysis theory and method research"(2015CB452802)+2 种基金National Program on Key Basic Research Project(2015CB452801)National Natural Science Foundation project"Observation and Assimilation Technology of Batch Variational Data and Its Application"(41475102)National Natural Science Foundation of China(41275025)
文摘On May 20 th 2007, a brief but severe downpour rainstorm occurred in the coastal areas of Maoming and Yangjiang with rainfall of 115 mm per hour. Data from NCEP/NCAR reanalysis with 1°×1° resolution, Doppler weather radar, conventional surface observations, high-altitude radiosonde and wind profiler radar were used to analyze characteristics and contributions of synoptic scale and mesoscale systems during this torrential rainstorm. The results showed that:(1) the storm was caused by a quasi-linear mesoscale convective system(MCS) and the slow-movement of this system was the primary trigger of the torrential downpour;(2) water vapor was abundant, nearly saturated and in steady state throughout the atmosphere before the storm; intrusion of the weak dry and cold air in the middle level and a striking "dry above and wet below " structure had increased the atmospheric instability;(3) low-level southwesterly airflow from a low pressure(trough) at the Beibu Gulf provided abundant water vapor at the onset of the rainstorm; a deep dry layer was formed by dry and cold air behind the high-level trough, which facilitated latent heat release;upper-level divergence and low-level convergence circulations also provided vertical uplift for warm and moist air at the lower level;(4) Topography only played a minor role as the MCS developed and strengthened over relatively flat coastal terrain. Low level density flow induced by convection triggered new convective cell generation at the leading edge of the convective system, thereby playing a key role in the change of temperature gradient at lower layers, and resulting in strengthening atmospheric instability.
文摘[Objective] The research aimed to analyze a regional rainstorm weather process in north-central Henan Province. [Method] Based on the conventional meteorological observation data and the rainfall data of Henan Meteorological Station, the diagnostic analysis of atmospheric thermodynamics and dynamics on a rainstorm weather process in north-central Henan Province on July 19, 2010 was carried out. The characteristics of physical quantity field and the evolution of weather situation in north-central Henan Province when the rainstorm happened were studied. [Result] Western Pacific subtropical high strengthened to extend westward. The dynamic uplifting of low vortex at the middle and low layers, the strong water vapor transportation of southwest low-level jet caused the regional rainstorm weather process in north-central Henan Province. The diagnostic results of physical quantity showed that the deep, thick wet layer and the sustained water vapor convergence provided the abundant water vapor for rainstorm generation. The positive vorticity advection center developed and spread from northwest to southeast, which was favorable for the development of vertical movement. The structure maintenance of positive vorticity at the middle and low layers, negative vorticity at the middle and high levels provided the power condition for the regional rainstorm generation. The pumping effect of convergence at the middle and low layers, divergence at the high layer was favorable for the strengthening of vertical ascending motion at the low layer. The uplifting effect of dew point front at the middle and low layers triggered the release of unstable energy. The confrontation of warm and cold air was one of the important reasons for the regional rainstorm. TBB characteristic analysis showed that TBB was from -60 to -50 ℃ in north-central Henan Province in the whole strong precipitation time, and the moving speed was equivalent to that of southwest vortex. The low-value belt of TBB corresponded with the rainstorm occurrence zone in Henan, and the minimum-value center of TBB was basically consistent with the strongest center of precipitation. [Conclusion] The research provided the scientific basis for the short-term forecast of rainstorm.
文摘[Objective] The aim was to study one rainstorm process being affected by two weather system. [Method] Influenced by high trough and Mongolia cold front, high latitude trough and subtropical high shear, rainstorm occurred in Jinzhou from October 19 to 22 in 2010. In order to make the analysis clear, there were two precipitation stages. Considering precipitation, weather situation, satellite image and numerical forecast, the rainstorm process was discussed. [Result] There were two raining stages during this precipitation. The first stage was affected by high altitude trough and ground Mongolia cold front, and the last stage was influenced by high altitude trough and subtropical high shear;the high latitude air, low latitude shear,low air torrent,subtropical high and their mutual coupling effect were the main influencing system and cause for this rainstorm. Satellite image suggested that there was convective cloud developing,weakening, disappearing and regenerating around the convective cloud of water vapor passage, showing distinct train operation state. The strengthening and weakening cloud image fitted the real precipitation. Numerical forecast precisely predicted the upper air and ground situation of the generation of rainstorm, especially the report of the east-retreating and south-falling trend of subtropical high;European center forecast fitted reality. There was certain error in predicting T639. Precipitation forecast was fine. [Conclusion] The study provided basis for the meteorological service work in future.
文摘[Objective] The aim was to comparatively analyze two local heavy rainstroms in northwestern Shandong Province, China. [Method] Based on the observation data from automatic weather station, sounding data and NCEP reanalysis data, two local heavy rainstorms at night on July 18 and August 9 in 2010 in northwestern Shandong was comparatively analyzed from the aspects of circulation situation, influence system and physical field, and the internal structure and possible formation mechanism of local heavy rain in Shandong were discussed further. [Result] The two rainstorms occurred in the forepart of southwest air in front of 500 hPa trough, and there was stronger atmospheric baroclinicity in the front zone near 850 hPa. The two rainstorms were affected by southwest warm and humid airflow at low level and shear line at 850 hPa; rainstorm often appeared in intensive area behind θse high-energy tongue, and rainstorm area corresponded with the area with high vertical speed well. From the differences, during the first rainstorm, there was obvious southwest low level jet and shear line at 700 hPa, and the area with high precipitation was located in the south of warm shear line at 700 hPa; during the latter rainstorm, there was no obvious southwest low level jet and shear line, and the area with high precipitation was located in the region between two high pressures. [Conclusion] The study could provide valuable thinking for the forecast of this kind of rainstorm in the future.
基金Supported by National Natural Science Fund (40975073)
文摘[Objective] A heavy rainstorm in Jincheng in August in 2010 was expounded. [Method] By dint of the conventional meteorological data, and automatic weather station data, and Doppler radar data, one severe torrential rainstorm was analyzed from the aspect of circulation background, physical quantity field, satellite cloud image, and radar echo, etc. [Result] The rainstorm was in the circulation field of low-west-east-obstruction, and was formed under the middle and low layer shear line and low air torrent situation. The low layer shear and convergence of wind favorable to the lift of unsteady air around Jincheng. The intrusion of cold air in the low layer of convective layer and above the ground trigered such convective weather. The torrent of the low air in the southwest sent abundant water vapor to the rainstorm area. The high temperature and the moisture accumulated much unsteady energy for the generation of rainstorm. The main precipitation system of this process was the singular of convective echo which was stimulated by the ground mesoscale shear line. Under the guidance of southwest airstream of the low and middle air, the convective echo singular formed train effect by moving towards Jincheng and formed large rainstorm. Doppler radar data suggested that the characteristics of the generation, development and movement of this mesoscale rainstorm system. The strong precipitation center was in the large value area of the gradient in the back of the TBB center. [Conclusion] The study provided references for the forecast and pre-warning of temporary rainstorm of such kind.
基金supported by the National Basic Research Program of China (973 Program, Grant Nos. 2013CB430105 and 2014CB441403)the National Natural Science Foundation of China (Grant No. 41205099)+1 种基金Guizhou Province Scientific Research Joint Project (Grant No. G[2013]4001)the Special Scientific Research Project of Meteorological Public Welfare Profession of China (Grant No. GYHY201006031)
文摘An extraordinary rainstorm that occurred in Beijing on 21 July 2012 was simulated using the Weather Research and Forecasting model. The results showed that:(1) The two precipitation phases were based on a combination of cold cloud processes and warm cloud processes. The accumulated conversion amount and conversion rate of microphysical processes in the warm-area phase were all much larger than those in the cold front phase.(2) 72.6% of rainwater was from the warm-area phase. Rainwater mainly came from the melting of graupel and the melting of snow, while the accretion of cloud water by rain ranked second.(3) The net heating rate with height appeared as an overall warming with two strong heating centers in the lower and middle layers of the troposphere and a minimum heating center around the melting layer. The net heating effect in the warm-area phase was stronger than that in the cold front phase.(4) Warm cloud processes contributed most to latent heat release, and the thermal effect of cold cloud processes on the storm in the cold front phase was enhanced compared to that in the warm-area phase.(5) The melting of graupel and snow contributed most to latent heat absorption, and the effect of the evaporation of rainwater was significantly reduced in the cold front phase.
