河南一次局地强降水过程的中尺度分析

Mesoscale Analysis of a Local Strong Precipitation in Henan

利用NCEP/NCAR再分析资料、常规观测资料,采用常规中尺度分析方法和Barnes滤波方法,对2013年6月7日14-20时林州站出现的一次局地强降水过程进行分析,结果发现此次降水过程是发生在东高西低的环流形势下,降水主要发生在500 h Pa低槽槽前;江淮气旋北端不断增强的偏东气流为降水区提供了充足的水汽条件;地形抬升有利于触发对流,并对降水有增幅作用。通过滤波分析发现,此次过程林州处于鞍型场中,且处于风向辐合线和风速辐合线附近;局地强降水发生在水汽通量负散度绝对值大值区与负散度绝对值大值中心重叠区。经过滤波前后对比发现,此次过程分析原始场得出的辐合上升运动区、水汽辐合中心、层结不稳定区与局地强降水落区有一定的偏差,而滤波场特征比较有指示意义。负散度绝对值大值区和地面中尺度辐合线附近有利于回波生成和发展;两回波带合并容易加强;短历时强降水发生前,垂直累积液态水含量迅速跃增;雷达径向速度辐合区有利于回波发展加强。

By using the NCEP / NCAR reanalysis data and conventional observation data,a local strong precipitation process occurred during 14 to 20 on June 7,2013 in Linzhou station was analyzed by the methods of the conventional mesoscale analysis method and Barnes filtering method. The results showed that this precipitation process occurred on east-high and west-low circulation situation and heavy rain occurred mainly in front of the low trough on 500 h Pa. East wind was growing in north of the Changjiang-Huaihe cyclone,which would provide adequate moisture for precipitation area. Topography flattening which could enhance the precipitation,is conducive to the convection. By using Barnes filtering method,it was found that Linzhou stayed in the pressure field of saddle type,and the wind direction convergence line and the wind speed convergence line were in the vicinity of it. Local heavy rain occurred in the vapor flux divergence big absolute value area and negative divergence overlap absolute value center.By contrast,it showed that the ascending motion area,the water vapor convergence center,stratification instability region in the original field diverged from the area of the heavy rain,while the bandpass filtering analysis had a good denotative meaning. Under favorable conditions including negative divergence of greater value and surface mesoscale convergence line,radar echo would have a growth spurt. The merger of two radar echo band would grow significantly. Before short-time strong rainfall occurred,the VIL had a quick growth.