近55年宁夏秋季降水的时空变化特征及其大尺度环流背景

Spatial-temporal variation of autumn rainfall in the last 50 years in Ningxia and its backgrounds on the large scale circulation

利用1951—2005年宁夏秋季降水、SST、NCEP／NCAR全球再分析资料及74个环流特征量，使用REOF、小波变换、相关分析等多种统计方法，分析了宁夏秋季降水的时空变化特征及其与SST和北半球500hPa高度场的遥相关。结果表明：近55年，宁夏秋季降水呈下降趋势，异常敏感区在宁夏北部和六盘山区；1979年前后发生突变，突变后降水明显减少，有显著的3年和6年左右周期变化；加利福尼亚西岸海区是影响宁夏秋季降水的SST关键区，3～5月是关键期，SST冷（暖）水位相与宁夏秋季降水偏多（少）相对应；3～5月加利福尼亚西岸海区SST在1979年前后发生突变，突变前后北半球中低纬度地区500hPa高度场变化显著，新疆脊、西太平洋副高和印缅槽是宁夏秋季降水的主要影响系统。

Using the data of autumn rainfall in Ningxia, SST, reanalyzed NCEP/NCAR and 74 circulation characteristics volumes during 1951 -2005 and the methods of REOF, wavelet transformand, abrupt change detected with Mann - Kendall and correlation analysis, spatial-temporal variation of autumn rainfall in Ningxia and its teleconnections with SST and 500 hPa height fields of Northern Hemisphere have been analyzed. The results showed that autumn rainfall decreased, particularly in the arid regions of the middle Ningxia in last 55 years ; northern Ningxia and Liupanshan area were abnormal sensitive areas;the abrupt change of autumn rainfall was detected before and after 1979 ,the rainfall decreased significantly after the abrupt change,there were about 3 years and 6 years significant periodic variations;the West Bank area of California was SST key areas and March to May was key period on impact of autumn rainfall in Ningxia. More （ or less） of autumn rainfall in Ningxia corresponds to the cold （ or warm） water phase of SST;the abrupt change of SST from March to May in the West Bank area of California was detected in 1979, there were significant changes on the 500 hPa height field of the middle-low latitude regions in Northern Hemisphere;with the increasing of SST after the abrupt change, the change of the atmospheric circulations was bad for autumn rainfall in Ningxia;the ridge in Xinjiang, subtropical high over the Northwestern Pacific, India-Burma trough were the major impact systems on autumn rainfall in Ningxia.