华北平原回流天气综合形势特征分析

Analysis of Integrated Characteristics of Returnflow Events in North China

利用历史天气图和NCEP再分析资料,普查了1980-2002年出现在华北平原地区的回流天气过程。依据500hPa环流形势,对华北平原的回流天气形势分为两种：两槽一脊型和高纬低压带型。针对不同的天气分型对产生回流天气的动力条件、水汽来源进行了合成诊断分析。结果表明：涡度和散度的垂直分布与一般的降水过程不同,低层存在辐散和反气旋环流;自东北南下经渤海回流到华北平原的空气是比较干的。该文分析结果有助于预报业务人员了解回流天气,提高华北回流天气的预报准确率。

Using the historical observation data and NCEP reanalysis data, an investigation is conducted on 31 returnflow events occurred over North China. On the basis of the 500 hPa circulation patterns, 31 events are divided into two types. The dynamical conditions and water vapor sources of these weather events, such as vorticity, divergence, vertical velocity, etc, are diagnosed. The results show that. （1） the dynamical conditions for returnflow events are a little different from other rainfall events, with divergence and anticyclonic circulation at lower levels; （2） the air of the returnflow from Northeast China, through the Bohai Sea, then to North China, is relatively dry.