我国西北和内蒙古地区春季沙尘暴的年代际变化及原因探析

利用1961—2005年西北及内蒙古地区208个地面气象站春季沙尘暴日数的观测资料，对沙尘暴发生的年代际变化进行了分析。结果显示,20世纪60年代和70年代沙尘暴偏多，80年代沙尘暴开始减少，90年代最少，21世纪的前5 a沙尘暴呈现出先增多后减少的趋势。基于1961—2005年的NCEP资料进行了原因探析，结果表明：①在沙尘暴多发年代，我国北方大部分区域风速出现了正距平，而在沙尘暴少发的年代，风速呈现出负距平;②在沙尘暴多发的年代，我国中高纬地区出现明显的气旋性流场距平，其南侧西风增强了我国西北及内蒙古地区偏西风风速，而在沙尘暴少发的年代，则与之相反;③极锋锋区在60—70年代强度偏强，从80年代开始强度呈现出明显的减弱趋势,21世纪初期锋区强度继续减弱,但其中心位置有小幅的自北向南移动。

Decadal Change of Spring Sand-dust Storm in Northwest and Inner Mongolia of China and its Cause

The decadal variation of spring sand-dust storm in northwest and Inner Mongolia regions of China during 1961 2005 was analyzed based on the daily sand-dust storm data from 208 weather stations. The result showed that the sand-dust storm events appeared frequently in 1960s and 1970s, decreased in 1980s, reduced to the minimum in1990s, and increased firstly and then decreased during 2001—2005. The cause of decadal variation of spring sand-dust storm was analyzed using NCEP data from 1961 to 2005, and the results were as follows: (1) There was positive anomaly of wind velocity in most areas of northwest China and Inner Mongolia Autonomous Region of China during the frequently-occurring periods of sand-dust storm, and there was negative anomaly of wind velocity in most areas of these regions during the least-occurring periods of sand-dust storm. (2) There was cyclonic flow field anomaly in most areas during the frequently-occurring periods of sand-dust storm, and there was anti-cyclonic flow field anomaly in most areas during the least-occurring periods of sand-dust storm. (3) There were intensive polar fronts in most areas during the frequently-occurring periods of sand-dust storm, and there were weak polar fronts in most areas during the least-occurring periods of sand-dust storm in study regions.