东半球500hPa闭合低压系统的统计分析

THE STATISTICAL STUDY OF EAST HEMISPHERE 500 HPA CLOSED CYCLONE

通过分析５００ｈＰａ东半球闭合低压系统，研究其气候规律。低压活动次数有年际、月际、季际变化。低压活动于中高纬度带，主要集中于两大地区，第一区是西太平洋及大陆东岸，第二区是东欧地区。第一区中心夏季向西移到大陆上，强度增大，对中国气候有重要作用。低压中心高度值的频数分布是双峰型。低压生命期比阻塞高压还长些。强低压主要出现在大陆高纬地带和西太平洋。强发展的低压多数出现在西太平洋。亚洲低压移动路径有两条，一条从西西伯利亚北部到库页岛。

Based on 10 year(1981-1990) historical weather maps (prepared by Beijing Meteorological Center),the statistical study of East Hemisphere 500 hPa closed cyclone is presented. The results indicate that the frequency of cyclones has inter annual variability and inter monthly change. The closed cyclones are concentrated on two large areas:Asian East Coast-West Pacific and East Europe.The center of the first area shifts to a more western position in the summer than in the other seasons and its frequency increases.The frequency distribution of cyclone center heights appears in a two peak type. The cyclone life cycle is longer than that of blocking high. The deep cyclones tend to appear in the regions of Asia European mid high latitude and West Pacific.The intensely devoloped cyclones appear in the region of West Pacific.The cyclones in Asia have two pathes:the northwestern and the western.