武汉20世纪90年代暴雨异常的物理环境变化背景探讨

DISCUSSION ON BACKGROUND OF PHYCICAL ENVIRONMENT VARIATION FOR RAINSTORM ANOMALY IN WUHAN IN 1990'S

根据武汉1951～2000年50年暴雨日数资料,应用Mann Kendall统计方法对暴雨序列进行年际突变检验。揭示出武汉暴雨在1979年发生突变,20世纪80年代后暴雨出现频数明显上升,强度增大,90年代达到最大。同时指出武汉20世纪90年代暴雨日数和暴雨量异常的显著特征。着重从西太平洋副热带高压、阻塞高压、太平洋海温等重要物理环境因子的突变出发,探讨造成20世纪90年代武汉暴雨异常的物理变化背景。结果表明,在武汉暴雨异常多的90年代与暴雨异常少的70年代,所对应的大气、海洋环境背景显著不同。90年代北半球500hPa月平均高度场是处于几十年中正异常最大的阶段,西太平洋副热带高压持续偏南、偏强、西伸脊点偏西;东亚中高纬度环流异常,维持稳定的阻塞高压形势;赤道东太平洋海温(SST)出现最大正距平,为近50年来的异常增温时期,厄尔尼诺(ENSO)事件发生频繁。

Based on the data of the number of days of rainstorms in the past 50 years from 1951 to 2000 in Wuhan ,some abrupt changes of rainstorms series have been tested using Mann_kendall method. It is revealed that the abrupt change of rainstorm in Wuhan occurred in 1979,and the frequency and intensity of the extreme rainstorm event obviously are increased since the 1980's, with the maximum in 1990's. Meanwhile, the anomaly characteristics of the duration and rainfall of rainstorms are analyzed. The background variations of major physical environment factors such as subtropical high pressure in western Pacific, and sea surface temperature(SST) in northern Pacific ,which led to the rainstorm anomaly in 1990's in Wuhan are discussed.The results show that the environment background of atmosphere and ocean was obviously differences in the anomaly more-rainstrom 1990's and the anomaly less-rainstorm 1970's, and the west Pacific subtropical high was much souther and stronger,and stable blocking high pattern was persistent in the middle and high latitudes over East Asia,and SSTin the equatorial eastern Pacific was positive departure,with frequent ENSO episode in 1990's.