西北地区春季多雨与少雨年的高空环流特征

对西北地区1961—2000年119个气象站的春季降水，分析了其空间分布和时间变化及其多雨与少雨年的500 hPa高度场、OLR场、700 hPa风场、湿度场。结果表明:多雨年中纬度500 hPa春季高度距平场东正西负,东亚大槽弱，欧洲低槽强，700 hPa春季矢量风距平场非洲至欧洲、西伯利亚海和菲律滨海盆为辐散区，印度和中国西北地区为辐合区，北半球欧亚700 hPa春季比湿距平场正中心位于阿拉伯海到孟加拉湾和长江流域，OLR主要负距平中心在东南沿海和孟加拉湾，西北地区亦为负距平，主要正距平中心在西太平洋。少雨年500 hPa春季高度距平场西正东负，中亚到新疆的高压脊强，东亚槽偏强，700 hPa春季矢量风距平场欧洲、西西伯利亚、泰国为辐合区，中国西北地区为辐散区，700 hPa春季比湿距平场正中心位于孟加拉湾和菲律宾海盆，OLR负距平中心在东南沿海—青藏高原北—新疆北部，西北地区亦为正距平，主要正距平中心在西太平洋。

High Circumfluence Characters in Spring-rainy Year and Drought Year in Northwest of China

Based on the spring precipitation data of 1961-2000 recorded at 119 meteorological stations in northwest of China,it has been analyzed for its space-time change,its 500 hPa high field and OLR distribution as well as 700 hPa wind field and specific humidity distribution in spring-rainy year and drought year.In rainy year,the 500 hPa high-field over middle latitude is positive in east and negative in west,the East Asian Low is weak and the Europe Low is strong;the 700 hPa vector wind is divergence field in areas of Africa-Europe,Siberia Sea and Philippine Sea Basin,and convergence field in areas of India and North China;the specific humidity field in North Hemisphere distributes in areas of Arabia Sea to Bengal Bay and the Yangtse River Basin;the main negative OLR anomaly centers locate in southeast seaboard,Bengal Bay and northwest regions,and the main positive in western Pacific Ocean.In drought year,the 500 hPa high-field is positive in west and negative in east,the high-pressure ridge from Mid-Asia to Xinjiang of China and the East-Asian trough are all strong;the 700 hPa vector wind is divergence field in northwest China and convergence field in areas of Europe,western Siberia and Tailand;the 700 hPa positive specific humidity field centers distribute in areas Bengal Bay and Philippine Sea Basin;the main negative OLR anomaly centers locate in areas from southeast seaboard to northern Tibet Plateau to northern Xinjiang,and the main positive in western Pacific Ocean and also in northwest China.