近50年来夏季西风指数变化与中国夏季降水的关系  

The Analysis of Relationship between the Variation of Westerly Index in Summer and Precipitation during the Flood Period over China in the Last 50 Years

作　　者：严华生[1] 胡娟[1] 范可[1] 张云瑾[1] 

机构地区：[1]云南大学大气科学系,昆明650091

出　　处：《大气科学》2007年第4期717-726,共10页Chinese Journal of Atmospheric Sciences

基　　金：国家自然科学基金资助项目40565001

摘　　要：使用1951~2002年夏季500 hPa高度月平均格点资料,运用多变量方差分析的方法,找到夏季不同雨带类型对应的西风指数变化关键区,再对关键区西风指数与夏季160个站的降水进行相关分析,找到降水显著高相关区。最后,采用NCEP/NCAR月平均再分析资料,通过合成风场检验的方法,找到高低西风指数年对应的风场显著差异区以及不同雨带类型对应的风场显著差异区,对高低西风指数和正常年西风指数各自对应的环流场以及三种类型雨带对应的环流场进行比较。研究发现,夏季西风指数差异最大的关键区在(35°N^55°N,110°E^140°E)。在关键区内,I类雨带对应高指数环流,II类雨带对应多年平均环流形式,III类雨带对应低指数环流。而降水场上的高相关区在长江和江南一带,为负相关。高低指数年的u、v风场显著性关键区和I、III类雨带的u、v风场的显著性关键区基本相同,经度在100°E^130°E,纬度分别位于35°N^55°N(A关键区)和25°N^30°N(B关键区)。高指数年对应I类雨带,在关键区A南风加强,在关键区B东风加强。低指数年对应III类雨带,在关键区A东北风加强,在关键区B西风加强。而多年平均环流形式对应II类雨带,A、B两个关键区主要是西风控制。归结原因是由于西风带的南进北退导致冷空气南下北上的路径、强度发生变化,从而影响夏季雨带的分布。Based on the grid point data of monthly mean 500 hPa height field in summer, the authors use multivariate analysis of variance to find the key area of westerly index which is closely related to rain-band patterns in summer over China. In order to find the precipitation area having high correlation with westerly index, the authors use westerly index of key area and precipitation data at 160 weather stations in summer over China to do correlation analysis. Finally, the authors use NCEP/NCAR data and significance test of wind field to find the key areas of high-index years and low-index years or among the three rain-band patterns, and analyze the feature of circulation of high-index years, low-index years and normal state and three rain-band patterns. It is found that the significant key area of westerly index lies in （35°N- 55°N, !10°E- 140°E）. In the key area, when it is the 1st rain-band pattern in summer, it will be high index circulation. However, when it is the 3rd rain-band pattern in summer, it will be low index circulation, and if it is the 2nd rain-band pattern, the circulation type is similar to the normal state. The high correlation area of precipitation field which is closely related to westerly index is over the Yangtze River and the south of the Yangtze River valley, and the correlation between westerly index and precipitation is anticorrelation. It is found that there are two key areas in wind fields of high-index years and low-index years, which consist with the wind key areas of the 1st and the 3rd rain-bands. The authors define the two wind key areas as key area A which lies in （35° N -55°N, 100°E - 130°E）, and key area B which lies in （25°N - 30°N, 100°E - 130°E）. For the high-index years or the 1st rain-band pattern, the south wind will intensify in key area A, and the east wind will intensify in key area B. Similarly, for the low-index years or the 3rd rain-band pattern, the northeast wind will intensify in key area A, and the west wind will intensify in key area B. And

关 键 词：雨带类型 西风指数 显著性关键区 相关场 风场关键区 

分 类 号：P461[天文地球—大气科学及气象学]