沙尘暴发生过程中的风速和土壤湿度变化

利用内蒙古中西部二连浩特、乌拉特中旗和乌海等3个地区2001—2004年的6小时风速风向观测资料和每小时的土壤湿度观测资料，以及同期的沙尘暴观测数据，统计研究了在沙尘暴发生季节，沙尘暴发生过程中风速与土壤湿度的关系和变化特征。结果表明，内蒙古中西部沙尘暴主要发生在春季，在这个季节，沙尘暴的发生主要受西风影响，沙尘暴发生过程中的风速达到最大，沙尘暴发生前和发生后风速变化较大，统计样本中的最大变幅达12m／s；统计样本中土壤湿度在沙尘暴发生前达到最小值，在沙尘暴发生过程中和发生后则没有明显的规律性的变化。土壤湿度是制约沙尘暴发生的较为重要的下垫面要素之一。

Change of wind speed and soil moisture during occurrence of dust storms

The characters of wind speed and instantaneous soil moisture content in the occurrence of dust storms are discussed in this paper,by using the wind speed and wind direction files,hourly soil moisture data and the corresponding dust storms data from 2001 to 2004 obtained from the meteorological observation stations of Erleahot,Wulatezhongqi and Wuhai,in the midwest region of Inner Mongolia.The three districts have level and open terrain,belong in the mid-temperate continental monsoon climate and are windy and cold in winter but hot and dry in summer.The result shows that dust storms mainly occur in spring.The prevailing wind in this season is western wind and the vegetation coverage rate is low in these regions,thus,dust storms occur frequently.When dust storms occur,the wind speed reaches the maximum,and it has a quick variation in the process before and after dust storms occurrence,which have a range of 12m/s in the statistics samples.The soil moisture kept the minimum just before the occurrence of dust storm,and it hasn't obvious regularity variation in this process.Soil moisture is one of the important factors of land surface restricting occurrence of dust storms.