DIAGNOSTIC ANALYSIS OF THERMAL AND DYNAMIC CHARACTERISTICS OF A RAINSTORM PROCESS IN SOUTHERN CHINA

LIN Xiao-xia; FENG Ye-rong; ZHANG Cheng-zhong; LIN Wen-shi

doi:10.16032/j.issn.1004-4965.2017.06.018

Abstract：Automatic weather observation data in Guangdong province and ECMWF_FINE reanalysis data are used to analyze a heavy rainfall in the south of China during 19-20 May 2015 with the focus on thermal and dynamic characteristics.The results show that the south of China was affected by an eastward-moving trough and heavy rainfall occurred on the south of a wind shear with a southerly warm airflow.The north rain-band(over the north part of theprovince)resulted from the front system,while the south rain-band(in the northwest part of the province)was in the warm sector of a front.There are significant differences about moisture transportation and power mechanism between the frontal and warm-sector heavy rain.Water vapor from Bay of Bengal and South China Sea played a dominant role in the rainstorm.During the process,the water vapor came in mostly from the southern and eastern boundaries and the whole water vapor transport based mostly on meridional transport.Frontal warm-sector had stronger moisture transport because of the stronger moisture-advection in the front area of strong moisture advection environment.As a result,precipitation over eastern Guangdong became greater.Divergence in upper-troposphere was more important than convergence in low-level,which is the significant dynamic property of precipitation in warm region.Besides,warm region has weaker rotation effects,distinct from the typical Meiyu precipitation.Analysis of the heavy rainfall process in terms of moisture potential velocity (MPV) principle shows that convective instability was the important mechanism for the development of heavy rainfall.The increase in vertical wind shear and moisture barocilinty around the low-level hasa great influence on the development of the vortex.Lower troposphere of rainfall area is controlled by the negative MPV,and the zone with large value of negative MPV has good correspondence with the location of heavy rain.