Abstract:

The characteristics of atmospheric circulation, climatic background, monsoon, SST and rainfall process of severe drought event occurred in the flood season of 2009 in Inner Mongolia were mainly analyzed in this paper. The results indicated that the less rainfall in flood seasons since 1999 in Inner Mongolia, the SST of the equatorial central and eastern Pacific entering into El Nino state in June of 2009 were the causes of the drought event in summer of this year. Moreover, the late onset and short lasting time over North China of South China Sea summer monsoon, and weak India summer monsoon were the main circulation background. In monthly mean height field at 500 hPa, a high pressure ridge at middle and high latitude of Eurasian continent had controlled Inner Mongolia region for a long time and a distribution of “west high east low” was shown in anomaly field, which were the main circulation patterns resulting in  severe drought in Inner Mongolia this year. And there was no effective precipitation in arid area. With the control of the high pressure ridge, the intensity of Northwest Pacific subtropical high had not changed the drought situation in Inner Mongolia.

摘要：

分析了内蒙古自治区2009年汛期发生严重旱灾的气候背景、海温、季风、大气环流和降水过程特点等，探讨造成干旱的可能成因。通过分析得出：1999年以来内蒙古汛期处于少雨阶段是2009年汛期干旱的气候背景；赤道中东太平洋海温异常增暖，南海夏季风爆发晚，且盛夏到达华北后维持时间短，印度夏季风偏弱是干旱的影响因子；500 hPa月平均高度场上，欧亚中高纬度上空的高压脊一直控制着内蒙古地区，在距平场上显示为西高东低的态势是干旱的环流形势；在高空高压脊的控制下，晴热高温加重了干旱程度；降水过程显示出干旱区域长时间无有效降水；在中高纬度高压脊的控制下，西北太平洋副热带高压在不同月份的强与弱均未改变内蒙古干旱的形势。

关键词: 干旱, 气候背景, 海温, 季风, 大气环流