Analysis of Characteristics of a Heavy Rainstorm Process in Nanchang City on July 7,2020

Based on the conventional observation data,dual polarization radar data and NCEP reanalysis data,the large-scale circulation background field,mesoscale conditions and formation causes of a heavy rainstorm in Nanchang on July 7,2020 were studied.It was found that this heavy rainstorm occurred under the weather background of the confrontation between the northward air flow behind the trough and the strong southwest warm and humid air flow to the northwest of the subtropical high.The divergence at the upper level,the shear in the middle and low levels,the southward movement of cold air at the low level,unusually abundant water vapor and high unstable energy caused the heavy rainstorm weather.In this process,under the influence of continuous eastward movement of several strong echo cells,an obvious"train effect"was formed in Nanchang,so that the local rainfall was continuous and intense.Moreover,the average of VIL was about 17 kg/m 2,and its variation characteristics were consistent with the variation trend of 5-min rainfall intensity,which had a certain indicator effect on short-term heavy precipitation.The topography of the Meiling Mountain in the west of Nanchang had a great influence on the formation and precipitation distribution of the heavy rain process.There was a strong rainstorm center near the mountain,and the precipitation was obviously larger than that in the plain area.

Analysis of Short-term Heavy Precipitations in a Regional Heavy Rainstorm in Shannxi Province

[Objective] This study aimed to analyze the cause of the generation of short-term heavy precipitations in a regional heavy rainstorm in Shannxi Province. [Method] Taking a heavy rainstorm covering most parts of Shaanxi Province in late July 2010 as an example, data of five Doppler weather radars in Shaanxi Province were employed for a detailed analysis of the evolution of the heavy rainstorm pro- cess. [Result] Besides the good large-scale weather background conditions, the de- velopment and evolution of some mesoscale and small-scale weather systems direct- ly led to short-term heavy precipitations during the heavy rainstorm process, involv- ing the intrusion of moderate IS-scale weak cold air and presence of small-scale wind shear, convergence and adverse wind area. In addition, small-scale convection echoes were arranged in lines and formed a ＂train effect＂, which would also con- tribute to the generation of short-term heavy precipitation. [Conclusion] This study provided basic information for more clear and in-depth analysis of the formation mechanism of short-term heavy precipitations.

Analysis of Predictability of a Large-scale Short-duration Heavy Precipitation Process in Nanchang City

Based on the observation data of automatic stations and sounding data,the circulation characteristics and physical quantities of a large-scale short-duration heavy precipitation process in Nanchang City on July 7,2020 were diagnosed and analyzed,and the ability of several numerical forecasting products to predict this process was tested.The results show that the short-duration heavy precipitation process was triggered in the process of the subtropical high changing from lifting to the north to retreating to the south under the weather background of the confrontation between the northerly flow behind the trough and the strong southwest warm and wet flow on the north side of the subtropical high.The strong southwest warm and wet flow provided abundant water vapor,and the southern pressing of the lower energy front and the invasion of the cold air near the surface layer provided unstable energy and dynamic conditions for the heavy precipitation.The changing trend of the subtropical high from lifting to the north to retreating to the south during 08:00 to 20:00 on July 7 was not predicted by numerical forecast,and there was a large deviation in the forecast of the time and intensity of the southern pressing of the northerly flow behind the trough,so the guidance of numerical forecast for heavy precipitation was not strong,which was not conducive to the prediction of the short-duration heavy precipitation.It was predicted that the subtropical high would move slightly to the south on July 6 compared with the previous day,and the forecast adjustment of the high-level weather system can be used as a sign of the forecast change,which needs to be paid certain attention in the daily forecast.

Analysis on A Heavy Rain to Rainstorm Weather Process in Liaoning Province

By using the synoptic chart,the physical quantity field,the satellite cloud image and the meteorological elements in the single station,a typical heavy rain to rainstorm weather process which occurred in Liaoning during August 18-20 in 2009 was comprehensively analyzed.The results showed that this process was a weather process which was affected by the upper trough and the subtropical high.Baikal Lake split cold air and Hetao cold air shifted eastward and formed the vortex.The subtropical high extended westward,lifted northward,and the warm wet airflow in the edge cut in.The low-altitude jet stream accelerated the transportation of water vapor,and several active meso-scale convective cloud clusters which appeared in 588 line periphery in the right side of high-altitude jet stream outlet gradually merged with the westerlies system.It caused that the strong mixed precipitation process occurred.

Analysis on the Reason of Local Heavy Rainstorm Forecast Error in the Subtropical High Control

[Objective] The research aimed to study the reason of local heavy rainstorm forecast error in the subtropical high control. [Method] Started from summarizing the reason of forecast error, by using the conventional ground observation data, the upper air sounding data, T639, T213 and European Center (ECMWF) numerical prediction product data, GFS precipitation forecast product of U.S. National Center for Environmental Prediction, the weather situation, physical quantity field in a heavy rainstorm process which happened in the north of Shaoyang at night on August 5, 2010 were fully analyzed. Based on the numerical analysis forecast product data, the reason of heavy rainstorm forecast error in the subtropical high was comprehensively analyzed by using the comparison and analysis method of forecast and actual situation. [Result] The forecasters didn’t deeply and carefully analyze the weather situation. On the surface, 500 hPa was controlled by the subtropical high, but there was the weak shear line in 700 and 850 hPa. Moreover, they neglected the influences of weak cold air and easterlies wave. The subtropical high quickly weakened, and the system adjustment was too quick. The wind field variations in 850, 700 and 500 hPa which were forecasted by ECMWF had the big error with the actual situation. It was by east about 2 longitudes than the actual situation. In summer forecast, they only considered the intensity and position variations of 500 hPa subtropical high, and neglected the situation variations in the middle, low levels and on the ground. It was the most key element which caused the rainstorm forecast error in the subtropical high. The forecast error of numerical forecast products on the height field situation variation was big. The precipitation forecasts of Japan FSAS, U.S. National Center for Environmental Prediction GFS, T639 and T213 were all small. The humidity field forecast value of T639 was small. In the rainstorm forecast, the local rainstorm forecast index and method weren’t used in the forecast practice. In the precipitation forecast process, they only paid attention to the score prediction of station and didn’t value the non-site prediction. Some important physical quantity factors weren’t carefully studied. [Conclusion] The research provided the reference basis for the forecast and early warning of local heavy rainstorm.

Study on Mesoscale Circulation Characteristics of Heavy Rainstorm in Wangmo County in Qianxinan on June 6,2011

[Objective] The aim was to analyze the causes of '6.06' heavy rainstorm in Wangmo County in Qianxinan.[Method] By dint of NCEP/NCAR 1°×1° reanalysis data,FY-2E TBB data,seven ground elements and two elements from automatic station data,the main influential system and all kinds of physical quantity field features of heavy rainstorm in upper reaches of Wangmo County in Qianxinan from the evening on 5 June to 08:00 on 6 June in 2011 were studied.[Result] The rainstorm was the result of cold air,which was provided by 850 hPa cold shear line and ground radiation line,and warm and wet airstream on the northwest edge of subtropical high.MCS was the main reason for such heavy rainstorm.Southwest warm and wet airstream in middle lower part provided sufficient water vapor for the rainstorm.The 850 hPa water vapor flux divergence center moved from north to south along ground convergence line to Qianxinan.Rainfall location and water vapor flux as well as convergence center were corresponding.The rainfall intensity also was consistent with the amount of water vapor flux and water vapor convergence.[Conclusion] The study provided reference for the report of heavy rainstorm.

ROLE OF A WARM AND WET TRANSPORT CONVEYOR OF ASIAN SUMMER MONSOON IN A BEIJING HEAVY RAINSTORM ON JULY 21,2012

A heavy rainstorm named Beijing "7.21"heavy rainstorm hit Beijing on 21 to 22 July 2012, which is recorded as the most severe rainstorm since 1951. The daily precipitation amount in many stations in Beijing has broken the history record. Based on the NCAR/NCEP reanalysis data and precipitation observation,the large-scale conditions which caused the "7.21"heavy rainstorm are investigated, with the emphasis on the relationship between it and an equatorial convergence zone, Asian summer monsoon as well as the tropical cyclone over the ocean from the Philippines to the South China Sea(SCS). The results indicated that a great deal of southerly warm and wet moisture carried by northward migrating Asian summer monsoon provided plenty of moisture supplying for the "7.21"heavy rainstorm. When the warm and wet moisture met with the strong cold temperature advection induced by cold troughs or vortexes, an obviously unstable stratification formed, thus leading to the occurrence of heavy precipitation. Without this kind of intense moisture transport, the rainstorm only relying on the role of the cold air from mid-and higher-latitudes could not reach the record-breaking intensity. Further research suggested that the northward movement of an Asian monsoonal warm and wet moisture transport conveyor(MWWTC) was closely related with the active phase of a 30-60 day intra-seasonal oscillation of the Asian summer monsoon. During this time, the monsoon surge triggered and maintained the northward movement of the MWWTC. In addition, compared with another heavy rainstorm named"63.8"heavy rainstorm, which occurred over the Huaihe River Basin in the mid-August 1963 and seriously affected North China, a similar MWWTC was also observed. It was just the intense interaction of the MWWTC with strong cold air from the north that caused this severe rainstorm.

Analysis of the Regional Heavy Rainstorm Caused by A Cooling Shear Line

By using the conventional data,the rainfall data in the automatic weather station and so on,a regional heavy rainstorm which happened in the northwest and north central region of Shandong Province during May 9-10,2009 was analyzed.The results showed that the cooling shear line in low altitude was the main system which caused the heavy rainstorm.The rainstorm mainly happened on the left front of jet stream in low altitude,the right of cooling shear line in low altitude and the northeast quadrant of vortex.The southwest jet stream in the west of subtropical high established a water vapor passage from the South China Sea to the center of North China.It not only provided warm and wet air and energy for the development of heavy rainstorm,but also was the necessary condition which shear line in low altitude stagnated for a long time.Ground frontal cyclone was the trigger mechanism of rainstorm.The northeast wet and cold air joined with the southwest warm and wet air in Shandong after the front,which prompted the development of convection and the release of instable energy to form the rainstorm.

Diagnosis and Analysis on the Heavy Rainstorm Weather Induced by " Higos" Weakened Circulation

The large-range heavy precipitation occurred in the central-southern coast of Fujian on October 6,2008.By using the conventional meteorological data and NCEP 1°×1° 6 h one time analysis data,we analyzed,diagnosed and discussed the reasons of this heavy rainstorm occurrence and maintenance.The results showed that this heavy rainstorm weather process was mainly formed by the low-pressure system which was remained after ' Higos' weakened.The low-pressure system was excited by the weak cold air in the low layer which was brought by 500 hPa westerly trough.The common effect of southwest jet stream in the low altitude in the southeast of low pressure and the northerly airflow in the northwest made that the low-pressure circulation strengthened and maintained.The calculation gained the physical quantity field configuration which was favorable for the appearance of heavy precipitation.The analysis on the relative helicity of windstorm showed that the distribution and the time evolution of helicity had the good corresponding relationship with the distribution and the time evolution of heavy precipitation.The intensity variation of helicity had the certain instruction significance on the rainstorm evolution.

A hybrid model for short-term rainstorm forecasting based on a back-propagation neural network and synoptic diagnosis

Rainstorms are one of the most important types of natural disaster in China.In order to enhance the ability to forecast rainstorms in the short term,this paper explores how to combine a back-propagation neural network(BPNN)with synoptic diagnosis for predicting rainstorms,and analyzes the hit rates of rainstorms for the above two methods using the county of Tianquan as a case study.Results showed that the traditional synoptic diagnosis method still has an important referential meaning for most rainstorm types through synoptic typing and statistics of physical quantities based on historical cases,and the threat score(TS)of rainstorms was more than 0.75.However,the accuracy for two rainstorm types influenced by low-level easterly inverted troughs was less than 40%.The BPNN method efficiently forecasted these two rainstorm types;the TS and equitable threat score(ETS)of rainstorms were 0.80 and 0.79,respectively.The TS and ETS of the hybrid model that combined the BPNN and synoptic diagnosis methods exceeded the forecast score of multi-numerical simulations over the Sichuan Basin without exception.This kind of hybrid model enhanced the forecasting accuracy of rainstorms.The findings of this study provide certain reference value for the future development of refined forecast models with local features.

Genetic Analysis of a Heavy Rainstorm on June 29,2006 in Henan Province

Based on conventional radiosonde data, surface encrypted observation data and so forth, the diagnostic analysis of a heavy rainstorm in the central and east of Henan Province on June 29, 2006 was carried out from the aspects of its large-scale background, environmental field and physical characteristics. The results showed that under the effect of a favorable large-scale environmental field, the rainstorm was caused by a mesoscale system. The high-east and low-west circulation pattern, the eastward movement of high-level low trough, low-level shear lines and strengthening of low-level jet streams directly resulted in the occurrence of the heavy rainstorm.

Analysis on "96. 8" Heavy Rainstorm Process in Handan

[ 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.

THE SYNTHETIC ANALYSIS OF THE VERY HEAVY RAINSTORMS IN GUANGDONG

Twelve very heavy rainstorms that caused severe floods in Pearl River drainage basin from 1949to 1994 are analyzed here. It is found that the rainstorms can be divided into three kinds. and they have differentcharacteristics in circulation and physical quantities. Rainstorms that caused floods in the Xijiang River andBeijiang River usually happen during the first flood season of the year (Apr.-Jun.). They last long. cover largeareas and cause severe disasters. There are Stable circulation backgrounds and complete tyontal precipitationsystems, and large stratification instability fields. Rainstorms often cause floods in coastal rivers and small tributaries during the second floods season (Jul.-Sept.). They happen suddenly, last a short time but have strong raillfail intensity. They are always caused by tropical cyclones but show significant instability only in rainstorm fields.The characteristics of rainstorms causing floods in the Dongjiang River or other main tributaries are similar to thetwo above. That is, they may be connected with fronts or tropical cyclones, and its stability degree is between thepreceding two kinds.

Mechanism Analysis of " 7·21" Extremely Heavy Rainstorm Process in 2012 in Beijing

Extremely heavy rainstorm occurred in Beijing on July 21,2012, which was the most serious since 1961. Based on analyzing the precipitation characteristics, formation mechanism of the rainstorm process was analyzed. Results showed that when the precipitation process occurred, it was stable east-high and west-low situation at 500 hPa, and there was a steady stream of water vapor transportation at middle and low layers and strong vertical ascending motion at 700 hPa. The distribution of physical quantity field （relative humidity, vorticity and divergence） showed that they were all benefited to the formation of rainstorm. Then, falling zone of rainstorm and the movement of rain belt, generation, development and weakening of precipitation were analyzed. Finally, according to circulation situation and the distribution of physical quantity at each layer, vertical distribu- tion of physical quantity and distribution of water vapor and jet stream, ＂7 · 21＂ rainstorm model was summarized.

Analysis on Formation Reason of a Local Heavy Rainstorm in Linyi Area

[Objective] The research aimed to study formation reason of a local heavy rainstorm process in Linyi from night on August 3 to early morning on 4th, 2010. [Method] Based on MICAPS weather chart, actual situation data of NECP analysis field, data of automatic encryption station and Doppler radar product, a local heavy rainstorm and extra heavy rainstorm process in Linyi from night on August 3 to early morning on 4th, 2010 was detailedly analyzed from weather background, meso- and micro-scale characteristics, physical mechanisms of occurrences and developments of meso and micro-scale systems. The formation reason of heavy rainstorm process was discussed. Moreover, we tried to find some occurrence rules of short-time strong precipitation. [Result] The local heavy rainstorm process had large short-time rainfall and obvious local characteristics. The main influence systems were subtropical high, westerly trough, meso- and small-scale ground low pressures. It was affected by many systems which had different scales and heights. The up-cold-down-warm unstable stratification accumulated a large number of unstable energy, which was basic condition of strong precipitation occurrence. It was convergence shear line at the bottom layer of airspace. The vertical shear and turbosphere of deep southwest-northwest-easterly airflow were at airspace. The common effect of up and down systems triggered generation of updraft, and made unstable energy release. For the release of unstable energy, after northwest airflow was cut off, the updraft made southwest airflow develop upward. It linked with easterly wave to form new vertical shear, which was a reason of long duration of strong precipitation. The southwest airflow at the edge of subtropical high was water vapor source of precipitation process, which provided sufficient water vapor supply for generation of heavy rainstorm. The system which was developing and strengthening would make the moving speed of system slow down. Then, the rainfall increased. It was a reason of long duration of strong precipitation. [Conclusion] The research accumulated certain experience for forecast work in future.

Analysis of a Heavy Rainstorm in Jincheng in August of 2010

[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.

Comparative Analysis of Two Local Heavy Rainstorms in Northwestern Shandong

[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.

Analysis on a Regional Heavy Rainstorm Process in North Henan

[Objective] The research aimed to analyze a regional heavy rainstorm process in North Henan.[Method] Based on routine weather chart,rainfall station in county and town,satellite cloud chart,etc.,by using synoptic diagnostic method,formation reason of the regional heavy rainstorm weather in North Henan during 18-19 August,2010 was analyzed initially from large-scale circulation background,influence system,physical quantity field and terrain influence.[Result] The strong precipitation had obvious meso-scale characteristics.The main influence systems were ground meso-scale convergence line,shear line at the middle and low layers,low-level southwest jet.The low-level southwest jet transported sufficient water vapor for generation of the heavy rainstorm.The ground converge line increased convergence ascending movement and water vapor convergence.Atmospheric divergence convergence center at the low layer was just in North Henan.Strong rise zone of the vertical velocity was also in North Henan.It provided sufficient dynamic condition for rainstorm generation.Generation,development and movement of the ground meso-scale convergence line had good indications for occurrence times and falling zones of the rainstorm and short-time strong precipitation.The big-value zones of K index and θse at the low layer both presented Ω distribution at the vertical direction,which had indicative significance for strong precipitation forecast.The strong precipitation center corresponded with fork horn terrain,and orographic rain characteristics were obvious.[Conclusion] The research provided reference basis for forecast of this kind of rainstorm.

Analysis of Heavy Rainstorm in Dongting Lake on July 4, 2014

This paper analyzes the heavy rainstorm in northeast Dongting Lake on June 4, 2014. Results indicate the weather situation, radar echo and the satellite imagery of the strong precipitation. Besides, the warm and wet water vapor in Dongting Lake also contributes to this heavy rainstorm. As the astronomical precipitation cycle in this precipitation is outstanding, it is essential to pay attention to and use the astronomical precipitation forecast method.

Design and Realization of Similar Report System of Moderate Rain,Heavy Rain and Rainstorm in Guyuan City

[Objective] The aim was to design and promote similar report system of moderate rain, heavy rain and rainstorm in Guyuan City. [Method] As C#. Net2005 development platform and based on MSSQLSEVER2005 database system, the upper air circulation during moderate rain, heavy rain and rainstorm from May to September since 1960, taking 500 hPa, 700 hPa and ground situation as complement, the similar height of 500 and 700 hPa were calculated. [Result]The system is set to be personal and template. The system only needs to be set for once. If the in- stallation is changed, the system doesn＇t need to change parameters. The system would automatically read the parameters and make it easy for the businessman to use. Meanwhile, it solves the problem of storing abundant data. Considering the promotion and application, the system is designed to be universal and portable, [ Conclusion] The system makes uP the Oossibilitv of mis-reoortina the moderate rain. heaw rain and rainstorm.