一次非典型暴雨中的MCSs特征及其形成条件

The Forming Conditions and Characteristics of MCSs in an Atypical Heavy Rainstorm Process

利用多种数据对2014年6月3-4日暴雨中的MCSs进行分析,结果表明：MCSs活动呈现出多尺度特征及多样化结构,即在中α-MCSs尺度中嵌套着中β-MCSs和中γ-MCSs,在形态上呈＂椭圆＂型和＂带状＂型,旧云团相互合并诱发出新的对流体是其活动的显著特点。在时间演变上,MCSs活动大致分为两个阶段,第一时段活动造成盆地南部和东北部的暴雨天气,第二时段活动造成盆地西部至南部的大雨到暴雨天气。分析MCSs的形成原因进一步表明,MCSs的发展与850h Pa盆地倒槽和暖湿南风气流极为密切,在对流层中部影响系统不明显的形势下,850h Pa倒槽及急流附近的湿、热环境及不稳定层结为对流提供了有利条件,如较大的CAPE值和上干下湿的湿度结构,K指数36℃以上,LI为负,且非地转湿Q矢量散度为负,这一序列物理量变化均是触发MCSs生成的重要因子。

Using a variety of data to analyze MCSs in the heavy rainstorm of the 3rd to 4th June 2014,the results showed that the MCSs display a multi- scale feature and diverse structure,namely that there were middle β- MCSs and γ- MCSs in the middle α- scale MCSs,and displayed the ＂ oval＂ type and the ＂ ribbon＂ type,old convective clouds combined with each other to induce new convection was a distinctive feature. According to the time evolution,MCSs activity roughly divided into two phases,the first phase activity caused the heavy rainstorm in southern and northeastern of Sichuan basin,the second time phase activity caused the heavy rain in south and west of the basin. Analyzing the cause of MCSs showed that the development of MCSs have close relation with the 850 h Pa basin inverted trough and warm,moist southerly wind,because the precipitation system of the middle troposphere was not typical,850 h Pa trough,moist- hot environment of near the Jet and unstable stratification provided favorable condition for the convection,such as greater CAPE values and the humidity structure of upper dry-lower wet,K index was above 36℃,LI index was negative,and the wet Q vector divergence was negative,the sequence physical variations were important factors to trigger MCSs growth.