2002年河南春季的一次层状云降水特征研究

A Study on the Feature of a Cloud System and Its Stratiform Cloud Precipitation in Spring in Henan Province

对2002年4月4—5日发生在河南省的大范围春季层状云降水进行探空、雷达、卫星等综合加密观测,分析了锋面移动过程中的云系特征和降水特点。结果发现此次降水主要是700～500hPa大气位势不稳定( θse/ z<0)造成的,位势不稳定区与地面降水极值中心有较好的对应。另外,在位势不稳定层出现前后,高空250～200hPa均存在一个急流中心,而在位势不稳定层的上方或下方则会有风向切变与之对应。云层厚度小、云顶高度低、云系结构不均匀是此次降水云系的主要特点。700～500hPa之间的位势不稳定度小、水汽输送量小和云顶温度低是造成此次降水量小的主要原因。

There was a widely precipitation on April 4-5,2002 in Henan Province.The features of the stratiform cloud system and its precipitation characteristics in a cold front are analyzed by using the intensified sounding and radar observational data,and the satellite pictures,etc.The result show that the precipitation results from the atmospheric potential instability between 700hPa and 500hPa,and the area of atmospheric potential instability (θ_se/z<0) corresponds to the maximum value center of surface precipitation fairly well.At the same time,a jet streamcore existing in 250~200hPa occurs before and after the formation of the atmospheric potential instability,and there is a wind direction shear above and below the potential instability layer.Small cloud depth,low cloud top height,inhomogeneous structure are the main characteristics of the precipitation cloud.Weak potential instability in 700~500hPa,small quantity of vapor transfer and low cloud top temperature are the main reasons for small precipitation in this precipitation process.