Various types of radars with different horizontal and vertical detection ranges are deployed in China, particularly over complex terrain where radar blind zones are common. In this study, a new variational method is developed to correct threedimensional radar reflectivity data based on hourly ground precipitation observations. The aim of this method is to improve the quality of observations of various types of radar and effectively assimilate operational Doppler radar observations. A mudslide-inducing local rainstorm is simulated by the WRF model with assimilation of radar reflectivity and radial velocity data using LAPS（Local Analysis and Prediction System）. Experiments with different radar data assimilated by LAPS are performed. It is found that when radar reflectivity data are corrected using this variational method and assimilated by LAPS,the atmospheric conditions and cloud physics processes are reasonably described. The temporal evolution of radar reflectivity corrected by the variational method corresponds well to observed rainfall. It can better describe the cloud water distribution over the rainfall area and improve the cloud water analysis results over the central rainfall region. The LAPS cloud analysis system can update cloud microphysical variables and represent the hydrometeors associated with strong convective activities over the rainfall area well. Model performance is improved and the simulation of the dynamical processes and moisture transport is more consistent with observation.
利用常规与加密气象观测资料、FNL再分析格点资料及FY-2G卫星云顶亮温(Temperature of Black Body,TBB)观测资料,对2015年7月14—15日湖北省梅雨期一次连续暴雨过程对流云活动的环境条件和导致短时强降雨的对流云影响方式进行了分析。结果表明:500 hPa位于西风槽前、850 hPa风场辐合、温度露点差较小及850—500 hPa暖平流为有利于湖北省对流云活动的环境条件。当天气尺度暖输送带云系在江南西部至长江中游地区建立,且低层暖切变线同时出现在湖北地区上空时,降雨明显增幅;当暖输送带云系明显东移后,湖北地区暴雨过程结束。当暖输送带位于湖北地区上空时,850 hPa相当位温平流项和对流项均为较大正值,且对流项大值区出现在平流项大值区的南侧。短时强降雨主要发生在降雨盛期,是构成湖北地区暴雨的重要组成部分。湖北省短时强降雨的4种对流云影响方式分别为对流云团西边界、深对流云团中心区、对流云串"列车效应"及对流云合并加强;其中,受对流云西边界、深对流云中心区或云团串影响的短时强降雨发生次数较多,受深对流云中心区和对流云合并加强影响的短时强降雨平均降雨量较大。
Mesoscale convective systems （MCSs） are classified and investigated through a statistical analysis of composite radar reflectivity data and station observations during June and July 2010-2012. The number of linear-mode MCSs is slightly larger than the number of nonlinear-mode MCSs. Eight types of linear-mode MCSs are identified： trailing stratiform MCSs （TS）, leading stratiform MCSs （LS）, training line/adjoining stratiform MCSs （TL/AS）, back-building/quasi-stationary MCSs （BB）, parallel stratiform MCSs （PS）, bro- ken line MCSs （BL）, embedded line MCSs （EL）, and long line MCSs （LL）. Six of these types have been identified in previous studies, but EL and LL MCSs are described for the first time by this study. TS, LS, PS, and BL MCSs are all moving systems, while TL/AS, BB, EL, and LL MCSs are quasi-stationary. The average duration of linear-mode MCSs is more than 7 h. TL/AS and TS MCSs typically have the longest durations. Linear-mode MCSs often develop close to the Yangtze River, especially over low-lying areas and river valleys. The diurnal cycle of MCS initiation over the Yangtze River valley contains multiple peaks. The vertical distribution of environmental wind is decomposed into storm-relative perpendicular and parallel wind components. The environmental wind field is a key factor in determining the organizational mode of a linear-mode MCS.
