2009年初内蒙古降水分布特征与成因

利用观测资料及NCEP再分析资料对2009年1—2月内蒙古地区降水异常的成因进行了初步分析。结果表明：2009年1—2月内蒙古西部、中部、东部偏南地区降水明显偏少,内蒙古东部偏北地区降水出现一定程度的增加。500 hPa高度距平特征表现为：以45°N为界,其南北两侧分别为正负距平区。这一环流特征是导致内蒙古东部偏北地区降水增多的原因之一,但对内蒙古中西部及东部偏南地区的降水异常并没有决定性的影响。内蒙古中部地区湿度条件和动力抬升条件均不利于降水,因而形成异常干旱;内蒙古东部偏南地区动力抬升条件有利于降水,但湿度条件不利于降水,实况降水的减少表明湿度条件是影响该地区降水的关键因素;内蒙古东北部地区湿度条件接近常年,而动力抬升条件明显有利于降水,因而导致降水增多。

Causes of Precipitation Difference over Inner Mongolia in Early 2009

A preliminary study is conducted on the causes of the precipitation anomaly event occurred between January and February of 2009 by using the observational and NCEP reanalysis data.The results show that during this period the height anomalies of 500 hPa at south of 45°N were positive while negative at north of 45°N,which induced more precipitation in the north-east part of Inner Mongolia and less precipitation on other parts;in the central part of Inner Mongolia,both humidity and ascending motion were not favorable for precipitation,and therefore there occurred a severe drought;in the south to east part,ascending motion was favorable for precipitation,but the humidity was not,resulting in drought owing to the dominant humidity;for the north to east part,humidity anomaly was not significant,but ascending motion was favorable for precipitation,resulting in more precipitation.