Relationship Between the Western Pacific Subtropical High and the Subtropical East Asian Diabatic Heating During South China Heavy Rains in June 2005

Based on the daily NCEP/NCAR reanalysis data,the position variation of the western Pacific subtropical high（WPSH） in June 2005 and its relation to the diabatic heating in the subtropical East Asia are analyzed using the complete vertical vorticity equation.The results show that the position variation of the WPSH is indeed associated with the diabatic heating in the subtropical East Asian areas.In comparison with June climatology,stronger heating on the north side of the WPSH and relatively weak ITCZ（intertropical convergence zone） convection on the south side of the WPSH occurred in June 2005.Along with the northward movement of the WPSH,the convective latent heating extended northward from the south side of the WPSH.The heating to the west of the WPSH was generally greater than that inside the WPSH,and each significant enhancement of the heating field corresponded to a subsequent westward extension of the WPSH.In the mid troposphere,the vertical variation of heating on the north of the WPSH was greater than the climatology,which is unfavorable for the northward movement of the WPSH.On the other hand,the vertical variation of heating south of the WPSH was largely smaller than the climatology,which is favorable for the anomalous increase of anticyclonic vorticity,leading to the southward retreat of the WPSH.Before the westward extension of the WPSH in late June 2005,the vertical variation of heating rates to（in） the west（east） of the WPSH was largely higher（lower） than the climatology,which is in favor of the increase of anticyclonic（cyclonic） vorticity to（in） the west（east） of the WPSH,inducing the subsequent westward extension of the WPSH.Similar features appeared in the lower troposphere.In a word,the heating on the north-south,east-west of the WPSH worked together,resulting in the WPSH extending more southward and westward in June 2005,which is favorable to the maintenance of the rainbelt in South China.

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.

Study on Temporal-spatial Distribution of Heavy Rain and Rainstorm in Different Functional Areas of Chongqing

To discuss response ability of five functional areas to rainstorm flood in Chongqing,by taking 8 districts（ counties） as research object,monthly occurrence times of heavy rain and rainstorm in different functional areas over the years and appearance month of the maximum rainfall were conducted statistics. Results showed that frequency distribution of heavy rain in whole year in different functional areas was different,but it was similar in the same functional zone. Temporal-spatial distribution of rainstorm was more independent,and there were different performances in various districts of each functional area. In urban functional core area and urban functional expansion area,rainstorm times was more,and the maximum precipitation was larger. In urban development new district,rainstorm times and the maximum precipitation were relatively smaller in whole Chongqing. In ecological conservation development area of northeast Chongqing,rainstorm duration was longer,and we needed prevention and control during June- September. In ecological protection area of southeast Chongqing,although rainstorm occurrence times was the most in Chongqing,the heavy rainstorm was less.

Analysis of Rainstorm Process in South China from September 7 to 8, 2022

Based on the NCEP data of the United States, a rainstorm process in South China during September 7 to 8, 2022 was studied. Synoptic method is a qualitative and empirical forecasting method. The results show that: In early September 2022, the cold air behind the trough line from northeast China to North China can directly drive southward and invade South China from the east road. Typhoon Hinnamnor is located in the saddle field between the mainland subtropical high and the offshore subtropical high. It moves northward on the west side of the coastal subtropical high, affecting the Taiwan Island and the coastal areas of East China. During September 7-8, the wave trough of the 925 hPa Easterly wave was located near 110°E. Easterly jet existed in the southeast of South China. The center of the easterly jet was located to the east of Hainan Island, which could transport abundant water vapor from the sea surface to the sky over South China. The precipitable water in the whole layer of the atmosphere decreased from the southern coastal areas to the north, reaching more than 50 mm in southern China, of which most of the South China Sea, Hainan Island and parts of the western part of Guangdong Province exceeded 60 mm, providing sufficient water vapor supply. The circulation field with convergence at low level and divergence at high level is conducive to vertical uplift to form precipitation.

Analysis of Simulated Heavy Rain over the Yangtze River Valley During 11-30 June 1998 Using RIEMS

RIEMS' ability to simulate extreme monsoon rainfall is examined using the 18-month (April 1997 September 1998) integrated results. Model-simulated heavy precipitation over the Yangtze River valley during 11-30 June 1998 is compared with the observation, and the relationships between this heavy rainfall process and the large-scale circulations, such as the westerly jet, low-level jet, and water vapor transport, are analyzed to further understand the mechanisms for simulating heavy monsoon rainfall. The analysis results show that (1) RIEMS can reproduce the pattern of heavy precipitation over the Yangtze River valley during 11-30 June 1998, but it is shifted northwestwards. (2) The simulated West Pacific Subtropical High (WPSH) that controls the East Asia Monsoon evolution is stronger than the observation and is extended westwards, which possibly leads to the north westward shift of the heavy rain belt. (3) The Westerly jet at 200 hPa and the Low-level jet at 850 hPa, both of which are related to the heavy monsoon rainfall, are reasonably reproduced by RIEMS during 11-30 June 1998, although the intensities of the simulated Westerly/Low-level jets are strong and the location of the Westerly jet leans to the southeast, which may be the causes of RIEMS producing too much heavy rainfall in the north of the Yangtze River valley.

The Influences of Boundary Layer Parameterization Schemes on Mesoscale Heavy Rain System

The mesoscale numerical weather prediction model (MM4) in which the computations of the turbulent exchange coefficient in the boundary layer and surface fluxes are improved, is used to study the influences of boundary layer parameterization schemes on the predictive results of the mesoscale model. Seven different experiment schemes (including the original MM4 model) designed in this paper are tested by the observational data of several heavy rain cases so as to find an improved boundary layer parameterization scheme in the mesoscale meteorological model. The results show that all the seven different boundary layer parameterization schemes have some influences on the forecasts of precipitation intensity, distribution of rain area, vertical velocity, vorticity and divergence fields, and the improved schemes in this paper can improve the precipitation forecast. Key words Boundary layer parameterization - Mesoscale numerical weather prediction (MNWP) - Turbulent exchange coefficient - Surface fluxes - Heavy rain This paper was supported by the National Natural Science Foundation of China (Grant No. 49875005 and No. 49735180).

Kinematic Structure of a Heavy Rain Event from Dual-Doppler Radar Observations

The detailed kinematic structure of a heavy rain event that occurred in the middle reaches of the Yangtze River was investigated using dual-Doppler radar observation. A variational analysis method was developed to obtain the three-dimensional wind fields. Before the analysis, a data preprocessing procedure was carried out, in which the temporal variation with the scanning time interval and the effect of the earth curvature on the data position were taken into account. The analysis shows that a shear line in the lower and middle levels played an important role in the rainfall event. The precipitation fell mainly on the south end of the shear line where southerly flow prevailed and convergence and updraft were obvious. With the movement and decay of the shear line, the precipitation moved and decayed correspondingly.

A Study on Water Vapor Transport and Budget of Heavy Rain in Northeast China

The characteristics of moisture transport and budget of widespread heavy rain and local heavy rain events in Northeast China are studied using the NCEP-NCAR reanalysis 6-hourly and daily data and daily precipitation data of 200 stations in Northeast China from 1961-2005. The results demonstrate that during periods with widespread heavy rain in Northeast China, the Asian monsoon is very active and the monsoonal northward moisture transport is strengthened significantly. The widespread heavy rainfall obtains enhanced water vapor supply from large regions where the water vapor mainly originates from the Asian monsoon areas, which include the East Asian subtropical monsoon area, the South China Sea, and the southeast and southwest tropical monsoon regions. There are several branches of monsoonal moisture current converging on East China and its coastal areas, where they are strengthened and then continue northward into Northeast China. Thus, the enhanced northward monsoonal moisture transport is the key to the widespread heavy rain in Northeast China. In contrast, local heavy rainfall in Northeast China derives water vapor from limited areas, transported by the westerlies. Local evaporation also plays an important role in the water vapor supply and local recycling process of moisture. In short, the widespread heavy rains of Northeast China are mainly caused by water vapor advection brought by the Asian monsoon, whereas local heavy rainfall is mainly caused by the convergence of the westerly wind field.

Study on Moist Potential Vorticity and Symmetric Instabilityduring a Heavy Rain Event Occurred inthe Jiang-Huai Valleys

In the light of the theory on moist potential vorticity (MPV) investigation was undertaken of the 700 hPa vertical (horizontal) component MP1 (MPV2) for the heavy rain event occurring in July 5–6, 1991. Results show that the distribution features of the two components were closely related to the development of a mesoscale cyclone as a rainstorm-causing weather system in the lower troposphere in such a way that the ambient atmosphere of which MPV1 > 0 and MPV2 < 0 with |MPV1| ≥ |MPV2| favored the genesis of conditional symmetric instability (CSI) and that, as indicated by calculations, a CSI sector was really existent in the lower troposphere during the heavy rain happening and contributed greatly to its development.

Relationship Between Persistent Heavy Rain Events in the Huaihe River Valley and the Distribution Pattern of Convective Activities in the Tropical Western Pacific Warm Pool

Using daily outgoing long-wave radiation （OLR） data from the National Oceanic and Atmospheric Administration （NOAA） and the National Center for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） reanalysis data of geopotential height fields for 1979-2006, the relationship between persistent heavy rain events （PHREs） in the Huaihe River valley （HRV） and the distribution pattern of convective activity in the tropical western Pacific warm pool （WPWP） is investigated. Based on nine cases of PHREs in the HRV, common characteristics of the West Pacific subtropical high （WPSH） show that the northern edge of the WPSH continues to lie in the HRV and is associated with the persistent ＂north weak south strong＂ distribution pattern of convective activities in the WPWP. Composite analysis of OLR leading the circulation indicates that the response of the WPSH to OLR anomaly patterns lags by about 1-2 days. In order to explain the reason for the effects of the distribution pattern of convective activities in the WPWP on the persistent northern edge of the WPSH in the HRV, four typical persistent heavy and light rain events in the Yangtze River valley （YRV） are contrasted with the PHREs in the HRV. The comparison indicates that when the distribution pattern of the convective activities anomaly behaves in a weak （strong） manner across the whole WPWP, persistent heavy （light） rain tends to occur in the YRV. When the distribution pattern of the convective activities anomaly behaves according to the ＂north weak south strong＂ pattern in the WPWP, persistent heavy rain tends to occur in the HRV. The effects of the ＂north weak south strong＂ distribution pattern of convective activities on PHREs in the HRV are not obvious over the seasonal mean timescale, perhaps due to the non-extreme status of convective activities in the WPWP.

Statistical Prediction of Heavy Rain in South Korea

This study is aimed at the development of a statistical model for forecasting heavy rain in South Korea. For the 3-hour weather forecast system, the 10 km×10 km area-mean amount of rainfall at 6 stations （Seoul, Daejeon, Gangreung, （Jwangju, Busan, and Jeju） in South Korea are used. And the corresponding 45 synoptic factors generated by the numerical model are used as potential predictors. Four statistical forecast models （linear regression model, logistic regression model, neural network model and decision tree model） for the occurrence of heavy rain are based on the model output statistics （MOS） method. They are separately estimated by the same training data. The thresholds are considered to forecast the occurrence of heavy rain because the distribution of estimated values that are generated by each model is too skewed. The results of four models are compared via Heidke skill scores. As a result, the logistic regression model is recommended.

Analysis of Causes for an Uncommon Persistent Heavy Rain During Winter

[Objective] The aim was to study the causes for one large scale of consecutive rainstorm process in the winter of 2010 in Guangxi. [Method] The characteristics and causes of the uncommon persistent heavy rain occurring in Guangxi in January, 2010 were analyzed by using synoptic observation data, NCEP 1°×1° per six hours Global Data Assimilation System reanalysis data and satellite image. [Result] The results showed that this persistent heavy rain process was associated with abnormal intensity and the stability of the western pacific subtropical high. The heavy rain was caused by the cloud system maintaining for a long time on the edge of subtropical high. The convergence of the infrequent southeast jet was the primary cause of the uncommon heavy rain. MPV1>0, and MPV2<0 at 700 hPa were the favorable conditions for the heavy rain. The magnitude of MPV1 and MPV2 was equivalent. [Conclusion] The study provided reference for the forecast of the following similar extreme weather.

RELATIONSHIP BETWEEN THE VARIATION IN HORIZONTAL VORTICITY AND HEAVY RAIN DURING THE PROCESS OF MCC TURNING INTO BANDED MCSS

Using real-time data and the WRF mesoscale model,a heavy rain event in the process of Mesoscale Convective Complex(MCC) turning into banded Mesoscale Convective Systems(MCSs) during 18-19 June 2010 is simulated and analyzed in this paper.The results indicated that the formation and maintenance of a southwest vortex and shear line at 850 h Pa was the mesoscale system that affected the production of this heavy rain.The low-vortex heavy rain mainly happened in the development stage of MCC,and the circular MCC turned into banded MCSs in the late stage with mainly shear line precipitation.In the vicinity of rainfall area,the intense horizontal vorticity due to the vertical shear of u and v caused the rotation,and in correspondence,the ascending branch of the vertical circulation triggered the formation of heavy rain.The different distributions of u and v in the vertical direction produced varying vertical circulations.The horizontal vorticity near the low-vortex and shear line had obvious differences which led to varying reasons for heavy rain formation.The low-vortex heavy rain was mainly caused by the vertical shear of v,and the shear line rainfall formed owing to the vertical shear of both u and v.In this process,the vertical shear of v constituted the EW-trending rain band along the shear line,and the latitudinal non-uniformity of the vertical shear in u caused the vertical motion,which was closely related to the generation and development of MCSs at the shear line and the formation of multiple rain clusters.There was also a similar difference in the positively-tilting term(conversion from horizontal vorticity to vertical positive vorticity) near the rainfall center between the low-vortex and the shear line.The conversion in the low vortex was mainly determined by бv/бp<0,while that of the shear line by бu/бp<0.The scale of the conversion from the horizontal vorticity to vertical vorticity was relatively small,and it was easily ignored in the averaged state.The twisting term was mainly conducive to the reinforcement of precipitation,whereas its contribution to the development of southwest vortex and shear line was relatively small.

Analysis of Deep Convective Towers in a Southwest-Vortex Rainstorm Event

The structure and organization of the extreme-rain-producing deep convection towers and their roles in the formation of a southwest vortex(SWV)event are studied using the intensified surface rainfall observations,weather radar data and numerical simulations from a high-resolution convection-allowing model.The deep convection towers occurred prior to the emergence of SWV and throughout its onset and development stages.They largely resemble the vortical hot tower(VHT)commonly seen in typhoons or hurricanes and are thus considered as a special type of VHT(sVHT).Each sVHT presented a vorticity dipole structure,with the upward motion not superpose the positive vorticity.A positive feedback process in the SWV helped the organization of sVHTs,which in turn strengthened the initial disturbance and development of SWV.The meso-γ-scale large-value areas of positive relative vorticity in the mid-toupper troposphere were largely induced by the diabatic heating and tilting.The strong mid-level convergence was attributed to the mid-level vortex enhancement.The low-level vortex intensification was mainly due to low-level convergence and the stretching of upward flow.The meso-α-scale large-value areas of positive relative vorticity in the low-level could expand up to about 400 hPa,and gradually weakened with time and height due to the decaying low-level convergence and vertical stretching in the matured SWV.As the SWV matured,two secondary circulations were formed,with a weaker mean radial inflow than the outflow and elevated to 300-400 hPa.

THE IMPACT OF DIFFERENT PHYSICAL PROCESSES AND THEIR PARAMETERIZATIONS ON FORECAST OF A HEAVY RAINFALL IN SOUTH CHINA IN ANNUALLY FIRST RAINING SEASON

An ensemble prediction system based on the GRAPES model, using multi-physics, is used to discuss the influence of different physical processes in numerical models on forecast of heavy rainfall in South China in the annually first raining season(AFRS). Pattern, magnitude and area of precipitation, evolution of synoptic situation, as well as apparent heat source and apparent moisture sink between different ensemble members are comparatively analyzed. The choice of parameterization scheme for land-surface processes gives rise to the largest influence on the precipitation prediction. The influences of cumulus-convection and cloud-microphysics processes are mainly focused on heavy rainfall;the use of cumulus-convection parameterization tends to produce large-area and light rainfall. Change in parameterization schemes for land-surface and cumulus-convection processes both will cause prominent change in forecast of both dynamic and thermodynamic variables, while change in cloud-microphysics processes show primary impact on dynamic variables. Comparing simplified Arakawa-Schubert and Kain-Fritsch with Betts-Miller-Janjic schemes, SLAB with NOAH schemes, as well as both WRF single moment 6-class and NCEP 3-class with simplified explicit schemes of phase-mixed cloud and precipitation shows that the former predicts stronger low-level jets and high humidity concentration, more convective rainfall and local heavy rainfall, and have better performance in precipitation forecast. Appropriate parameterization schemes can reasonably describe the physical process related to heavy rainfall in South China in the AFRS, such as low-level convergence, latent heat release, vertical transport of heat and water vapor, thereby depicting the multi-scale interactions of low-level jet and meso-scale convective systems in heavy rainfall suitably, and improving the prediction of heavy rainfall in South China in the AFRS as a result.

On the Development of Meso-Scale Heavy Rain Parcels in China

Heavy rains occur in China frequently, which often bring us floods and serious disasters in the summer half-year. The meso-scale heavy rain parcels (MHRP) in the mid-latitude are usually developed in following cases:I.By the approaching, meeting and / or overlapping of different weather systems, when two or more different rainfall systems are getting to conjugate, some MHRPs could be developed, such as: 1) a new cold/warm front or squall line approaches an old front or squall, even when the old one is somewhat decrepit; 2) at the places where two or more synoptic systems with different characteristics are meeting together, such as the meeting of tropical cyclone with the cold airs coming from the mid- and / or high-latitudes, or the low latitude vortex meeting with the westerly trough; 3) at the intersections of some different weather systems, such as the intersection of drylines, squall lines or fronts moving from different directions; and 4) by the overlapping of rainfall parcels produced continuously from a meso-generation centre.II.Resonance Effect and Tibetan Plateau Influence are two reasons why high frequency of heavy and torrential rains arround the meiyu front is discussed also.

Analysis of the Process of Extreme Heavy Rainfall in the Cold Lake in Qinghai

[Objective] The aim was to analyze the process and reason of the extreme heavy rainfall on June 15,2011 in Cold Lake in Qinghai.[Method] The weather,physical field and satellite of one extreme heavy rain in the cold lake in Qinghai were expounded.[Result] The formation of the loop 'crooked neck' of high pressure,which on the one hand posed a typical situation in the circulation of heavy precipitation in Qinghai,and on the other hand,formed the southwest,southeast of the two water vapor transport in air,in addition to the small groove from the trough of Lake Balk hash and the split vortex plateau,resulted into the extreme heavy rainfall in Cold Lake.The presence of thermal low pressure 700 hPa was conducive to the accumulation of low energy and low-level moisture transport from the Qinghai region to the south of Qaidam Basin.[Conclusion] The resulting process was mainly due to heavy rain in the lower troposphere convergence,high-level divergence,high humidity areas and a strong vertical upward motion.

Study on the Prediction Method of the First Heavy Rain in the Spring of Xi'an City Based on Markov Chain

[Objective] The aim was to study the Markov chain prediction method of first heavy rain in spring in Xi’an City.[Method] According to the dependent random variables of the occurrence of heavy rain,precipitation in spring in seven meteorological stations in Xi’an City from 1959 to 2010 was selected.Its occurrence date was determined by the standard of first heavy rain in spring in meteorology.According to the length of the sequence of the problem and actual situation,six states were divided.And by dint of Markov chain,first heavy rain prediction model in spring was set up.[Result] The predicted occurrence time of first heavy rain in spring in Xi’an in 2009 and 2010 was consistent with the actual situation.The prediction effect was fine.The method had clear thought and was convenient for calculation,with certain dependence and practicality.[Conclusion] This method provided reference value for the actual forecast of first heavy rain in spring.

Conventional Analysis on a Heavy or Torrential Rain Weather Process

[Objective] The research aimed to analyze a turning weather process in Binzhou City of Shandong Province in midsummer of 2010.[Method] Started from the short-term forecast ideas,the formation reason of heavy or torrential rain and local heavy rainstorm in Binzhou City during 4-5 August,2010 was analyzed from the circulation situation,physical quantity field,radar echo and so on.[Result] The westerly trough and cold air were the trigger mechanisms of precipitation.The warm wet air flow at the edge of subtropical high and the high-altitude low trough were the main systems of precipitation.It was the typical precipitation process that the northwest of subtropical high overlapped with the westerly trough.In the prior period,the high temperature continued.The cold air at 500 hPa made the convection strengthen.It was the main reason that the local precipitation was strong.In the forecast of rainstorm,the specific humidity,K index and SI index were the good physical quantities and reference indexes.In the formation process of rainstorm,K index had the increasing process.When the rainstorm finished,or the rain intensity weakened,K index decreased obviously.SI index indicated the development of convective precipitation.The radar echo analysis found that the mesocyclone appeared in the process for a short time.For it weakened quickly and disappeared in the shift process,the strong precipitation and gale were formed in the west of Binzou,but the hail wasn’t generated.[Conclusion] The research provided the experience for the forecast of such weather in future.

Analysis on the Radar Echo's Characteristics of One Severe Rainstorm in Central Guangxi

[Objective] The aim was to analyze radar echo characteristic of a heavy rainstorm in central Guangxi in June, 2010. [Method] Using conventional observations and automatic stations, Doppler radar and other data, a severe rainstorm in central of Guangxi which occurred on 31 May to 1 June 2010 was analyzed. The characteristics of weather radar data were analyzed to reveal the characteristics of radar echo during the heavy precipitation process. [ Result] The heavy rainstorm had gone through many singular wind storms towards MCS variation. The existence of ultra-sin- gular and ＂train effect＂ was the main reason of the heavy rainstorm. The results showed that during the heavy rainfall experienced an evolution process from multi-cell storm to MCS, and found that super cell and the ＂train effect＂ was the major reason which caused this torrential rain. The echo centroid of multi-cell storm stretching along its moving reverse order was the key factor which maintained the heavy rain. Analysis also found that the average echo intensity had a good relationship with rainfall. Strong echoes were in quasi-stationary state for a long time and was favorable heavy rain. In the diameter velocity diagram, mesoscale convergence line, the adverse wind regions and the mid-cyclone were the important basis to determine producing and keeping heavy rainfall. Radar wind profile can reflect the configuration of layers of wind conditions, and it was an effective tool to determine whether the trough was in transition or not. [ Conclusion] The study provided reference for the short-term and nowcasting report.