阿拉善盟春季沙尘暴变化特征及气候成因分析

Variation Characteristics and Climatic Origins of the Sandstorm in Spring of Recent 40 Years in Alax League

利用1981—2020年阿拉善盟9个国家气象观测站的逐日沙尘暴资料和NCEP/NCAR逐月再分析资料,分析了阿拉善盟春季沙尘暴发生、演变特征及沙尘暴偏多年、偏少年的环流场及前冬海温场特征。结果表明:阿拉善盟春季沙尘暴日数及沙尘暴过程均呈明显下降趋势。春季沙尘暴偏多年,亚洲大陆为经向环流控制,东亚大槽偏强,反气旋性气流前部西北风与气旋性气流后部偏北风在阿拉善盟上空辐合加强,极地冷空气沿乌拉尔山高压脊前偏北气流入侵,从而导致春季沙尘暴偏多;前冬海温场为北太平洋海温、印度洋海温、北大西洋海温冷水位相,赤道中东太平洋海温为暖水位相。春季沙尘暴偏少年,亚洲大陆为纬向环流控制,东亚大槽偏弱,阿拉善盟多为高压脊控制,上空为气旋性气流前部西南风与反气旋性气流后部的东南风汇合,不利于冷空气南下,沙尘暴较少发生;前冬海温场为北太平洋海温、印度洋海温、北大西洋海温暖水位相,赤道中东太平洋海温为冷水位相。

In this study,the observed sandstorm data from 9 meteorological stations in Alax League and monthly reanalysis data from NCEP/NCAR during 1981—2020 are used to analyze the occurrence and evolution characteristics of the sandstorm and the circulation characteristics in spring in the years with more and less sandstorms,as well as the sea surface temperature(SST)in early winter.The results show that the numbers of days and processes of the sandstorm have a significant declining trend.In the spring of the year with more sandstorms,the Asian continent is controlled by the meridional circulation.The east Asia deep trough is strong.The convergence caused by the northwesterly in front of the anticyclone and the northerly behind the cyclone over Alax League is enhanced.The cold air from the polar region invades along the northerly in front of the Ural high pressure ridge.All these conditions result in more sandstorms in spring.The SSTs in North Pacific,Indian Ocean and North Arctic Ocean display a cold phase,while the SST in the Equatorial Middle East Pacific shows a warm phase.In the springs of the year with less sandstorm,the Asian continent is dominated by zonal circulation.The east Asia deep trough is weak.The high pressure ridge is dominant over Alax League.The convergence caused by the southwesterly in front of the cyclone and the southeasterly behind the anticyclone is not conductive to the southward movement of the cold air.Therefore,the sandstorm is less.The SSTs in North Pacific,Indian Ocean and North Arctic Ocean display a warm phase,while the SST in the Equatorial Middle East Pacific shows a cold phase.