| The Jianghuai area,located in the East Asian Monsoon region,has large variability in its summer rainfall amounts,especially after the 1980s,the persistent regional heavy rainfall events frequently occurred over this region causing devastating damages and socioeconomic consequences.The earlier studies mostly focused on the several specific heavy rainfall events and lacked of systematical classifications of the latest events,partly due to the complexity of the formation of summer heavy precipitation over this region.Moreover,it is still a great challenge for most models to accurately predict the summer precipitation over this region and the microphysics processes in the model have shown large impacts on the model rainfall simulation.Hence,it is of great importance to systematically classify the weather patterns by comprehensively analyzing the heavy rainfall processes during the recent years,and to conduct a series of model experiments based on the representative cases for each category,with emphasis on the effects of microphysics parameterizations.The results can be beneficial to improve the skills of WRF model in predicting the regional heavy rainfall events over the Jianghuai area.This study firstly examines all the regional heavy rainfall events over the Jianghuai area during the year of 2003 to 2012 by using the hourly rainfall data at 368 stations in the Yangtze river region,and for using hourly precipitation data with higher resolution,make systematic classification of rainfalls in 2008 to 2012 according to the key weather patterns using the 6-hourly NCEP FNL high-resolution reanalysis data.All the persistent regional heavy rainfall events are dividied into three main categories:The type associated with stationary front,the type directly associated with typhoon or with its spiral rain band,and the type associated with strong convection along the edge of Subtropical High.Based on the above three main types of weather patterns causing the persistent regional heavy rainfall over the Jianhuai area,this study selects representative,cases from each type and makes 16 groups of comparative experiments for each case using the WRF v3.5.1 model with 8 different microphysical schemes(Kessler,Purdue Lin,WSM3,WSM5,Eta Ferrier,WSM6,Goddard and Tompson)and 2 cumulus parameterization schemes(KF and BMJ).A local short-time rainstorm event in Shanghai is also simulated to make comparison with the persistent regional heavy rainfall events.These experiments focus on exploring suitable scheme combination for different kinds of rainfall by fully examining the precipitation TS score,precipitation area,intensity,center as well as the circulation situation under different combinations of microphysics and cumulus parameterization schemes.The main conclusions were summarized as follows:(1)Two cumulus convection parameterization schemes have systematic but different impacts on model simulations of regional heavy rainfall events over Jianghuai area under different weather patterns.The BMJ cumulus scheme systematically shows better capability than the KF cumulus scheme for the first and third type of rainfall,while the KF scheme is better than the BMJ scheme for the second type of rainfall.Among them,KF scheme simulated stronger intensity than BMJ in stationary front type;In typhoon rainfall events,the pattern correlation of KF scheme is generally greater than the BMJ,and KF better produces the rainfall intensity compared to the observation;In the type of strong convection along the edge of Subtropical High,the change of the cumulus convection schemes has less effect in simulating the precipitation area,and all model simulations tend to produce the rainfall areas shifting towards south compared to the observations.But the cumulus choice has the great influence on rainfall intensity,with the BMJ better capturing the rainfall intensity.(2)The sensitivity of different microphysical schemes to model simulations with respect to different types of heavy rainfall events is different when different cumulus parameterization(KF or BMJ)is combined:The choice of cumulus parameterizations has great influence to all microphysical schemes for the second and the third types of heavy rainfall,while for the first type of rainfall,the WSM5 and the WSM6 microphysics schemes are not sensitive whether coupling with KF or BMJ.But the Kessler scheme showed lowest sensitivity to cumulus parameterizations and the worst pattern correlation to the observations.(3)The microphysics parameterization schemes have large impacts on the location and intensity of regional heavy rainfall centers,but with different performance.a)For the type associated with stational front,Ferrier-BMJ scheme mostly realiscitally simulates the pattern of rainbands(PC=0.80),and captures the precipitation center and intensity along the low level jet.It better forecasts the westerly trough moving eastward at 500 hPa,and the shear line accompanied with mesoscale low vortex compared to other schemes.b)For the type associated with typhoon or peripheral spiral rain band,Thompson-KF scheme not only forecasts the precipitation areas,center position and intensity accurately,but also has higher scores for daily precipitation above medium,heavy and torrential intensity.This scheme combination most realistically captures the asymmetry structure of typhoon and predicts the abundant water vapor transport as observations and the subtropical high position was the closest to the observations.c)For the type associated with the strong convection along the edge of Subtropic High,Lin-BMJ scheme well captures the major rain belt,and better simulates the center position and intensity of the heavy rains.Especially,it has the highest TS score for the highest intensity of precipitation.The reason of this success is because the Lin-BMJ best captures the position of Subtropical High.d)The effects of three microphysics schemes(WSM5,WSM6 and Lin)on the regional heavy rainfall events over Jianghuai area differ in that on local short-time rainstorm of Shanghai even occuring under the same weather types.Based on comprehensive analysis of precipitation area,heavy rain center location,intensity,wind field,geopotential height,and K index,it shows that WSM5-BMJ scheme is the optimal choice because it mostly realistically simulates the center of heavy rains and the circulation patterns,although it produces stronger rainfall intensity due to larger snow particle mixing ratio. |
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