A Study Of Radar Observation And Numerical Simulation Of Mesoscale Convective Systems In The Weibei Area Of Shaanxi Province

Based on the 711-digital weather radar data in Weibei area of Shaanxi Province between May and September from 2000 to 2006, 335 cases of mesoscale convective system (MCS) were classified into three classes (cell, linear and areal MCS) and nine sub-classes (slightly moving cell, moving cell, merging cell, trailing stratiform (TS), leading stratiform (LS), parallel stratiform (PS), broken linear, broken areal and embedded areal MCS). In this paper, the summary characteristics of each MCS class were statistically analyzed, which included frequency, diurnal variation, duration, scale and moving speed of echo. By applying WRF mode, once case of MCS happened on May 30, 2005 in Weibei area of Shaanxi Province is simulated and analyzed by microphysics scheme, Thompson, Kessler, Ferrier, Lin, WSM3, WSM5, WSM6. The results show:(1) The areal MCS was found to be the dominant mode of all kinds of MCS organization, the isolated cell and linear MCS composed 53% of the studied population. The frequency of times of MCS initiation is displayed that most of the systems were initiated between 1100 and 2100 BST, which corresponds to the afternoon and evening hours of the China. The linear MCS cases occurred between 1300 and 2100 BST, with a smaller case in linear MCS between 0200 and 1200 BST. The areal MCS have occurred any times in a day, but the main initial time between 1000 and 1700 BST. The unmoving cell MCS was the smallest mean duration (1.6h) and the smallest mean scale (7.42km) in nine subcategories, and the non-embedded areal MCS was the greatest mean duration (4.4h) and the greatest mean scale (102.98km). The moving speed of the TS MCS was the most, an average of 33 km/h.(2) The linear MCS was formed hail with maximum probability, and cell MCS with minimum probability, and that TS MCS tended to bring about severe weather disaster, and slightly moving cell MCS produce light disaster.(3) The simulated results of seven explicit cloud microphysical schemes all show that virtual heavy precipitation center is appear in south of Shaanxi province, and WSM6 scheme simulated cumulative rainfall and observation rainfall of 6 hours show best agreement in Weibei area and North of Shaanxi province. Simulated intensity and region of 6 hours cumulative rainfall by each scheme is similar, but the rain region is smaller in Weibei area than real rain. Thompson scheme is best to simulate 24h rainfall. WSM6 scheme is better to simulate hourly precipitation.(4) The Xi'an station sounding curve of simulation by each explicit microphysics scheme and measured curves are very similar. Showalter Index (SI) by WSM3 scheme is best simulated.