【摘要】 选取1960~2011年内蒙古104个测站春季(3~5月)降水资料和NCEP/NCAR再分析资料,分析内蒙古春季降水特征和典型干旱和多雨年同期和前期大气环流特征。结果表明:内蒙古春季降水呈从东到西,从南到北减少的分布;春季以干旱少雨为主,每个年代都有两年或三年的连续干旱发生;90年代后降水的异常偏多和偏少的频率显著增加;干旱少雨年同期500hPa中高纬度欧亚距平场呈"-+-"的分布,表现出中亚高压脊强盛,东亚槽深厚的特征。多雨年与干旱少雨年相反,欧洲大陆为正距平中心,内蒙古中西部及其上游的蒙西山地和西西伯利亚平原为负距平,中国大陆东部沿海、日本岛为正距平中心,表明内蒙古上游地区高压偏弱,下游东亚大槽位置偏东,中高纬度以纬向环流为主。850hPa径向距平风场显示,在干旱少雨年,西亚和南亚地区均为西北气流。多雨年孟加拉湾一直到俄罗斯东部均为南风距平。干旱(多雨)年前期乌拉尔山高压脊强盛(偏弱),东亚大槽位置偏西(偏东),贝加尔湖为高压槽(脊)。更多还原

【Abstract】 The precipitation data in spring( March- May) 1960- 2011 were collected from 104 weather stations and NCEP /NCAR reanalysis data and precipitation anomaly percentage were used to evaluate the drought and rainy climate characteristics and analyze the regional temporal atmospheric circulation features in drought years and rainy years. The outcomes prove: In spring,eastern region and southern regions had higher precipitation than western and northern regions. Eastern agricultural areas and northern pastoral areas experienced more drought years; Northeastern agricultural areas and forest areas were recorded having significant higher number of rainy years; Mid- western agricultural areas and cities met similar numbers of drought and rainy years. The whole regions leaned to be dry before 1990 s,meanwhile tended to be rainy from 2000 to 2011. Nonetheless,the record of abnormal precipitation significantly increased after 1990 s. In drought years,500 hPa anomalies and middle and high latitudes Eurasian anomalies were in "- +- " distribution. 850 hPa radial wind anomalies presented that in drought years,northwest flow controlled the West Asia and South Asia; the strong cold air mass prevented the transportation of southwest warm air towards north. In rainy years,southerly anomaly covered the areas from Bay of Bengal to Eastern Russia,with strong southwest airflow upon westerlies; southwest warm air towards northerly. In pre- drought period,Ural ridge became powerful,East Asian trough positions westerly;Trough is on Lake Baikal. In pre- rainy period,Ural ridge became weak,East Asian trough positioned easterly;Ridge was on Lake Baikal.更多还原