我国西北地区黑风暴的成因和对策

通过对我国北方地区气候资料分析，揭示了沙尘暴的时、空分布特征，并指出西北地区春季４、５月份常发生黑风暴天气的宏观气候背景和下垫面条件。同时以１９９３年５月５日发生的黑风暴天气过程为例，探讨了造成西北地区大范围黑风暴天气的大尺度环流形势，主要天气系统和中尺度系统。有针对性地提出预报着眼点和防灾、减灾对策。

STUDY ON THE FORMATIVE CAUSES AND COUNTERMEASURES OF THE CATASTKOPHIC SANDSTORM OCCURRED iN NORTHWEST CHINA

By analysing the thirty-year(1951-1980)climatological data and the catastrophicsandstorm case which happened in Northwest China on 5 may 1993.the analytical results wereconcluded as follows:(1) In North China,sandstorm occurred more frequently in the Northwest than in the Northeast.There were two areas (the east of Gansu Hexi Orridor and the southwest of the Taklimakan Desert)where sandstorm happened more frequently than any other areas.The frequency of the sandstormoccurring in April was the highest in the whole year.The frequency of the sandstorm happonning inspring was nearly a half of that in the whole year.(2 )There are three causes which lead to sandstorm mainly happenning in Northwest China inspring season. First, weather is arid and the soil is porous.second, the position of subtropical jetstream is advantageous to frequently forming strong wind. Finally,the convective activity resultingfrom the unstability of the atmosphere is beneficial to the drop-transmission of the momentum from thejet stream.(3)The large- range sandstorm and local catastrophic sandstorm occurring on 5 May 1993 weredue to the passages of the strong cold front.The low-pressure system in the northeast of the Qinghai-Xizang Plateau,the low-level eastcrly jet over Gansu Hexi Orridor and meso-scale squall line alsoplayed an important role in forming the catastrophic sandstorm. (4)The main emergency countermeasures are to take prevention as the dominant factor,that is,the local meteorological observatory must provide timely and accurate weather prediction aboutcatastrophic sand storm for the local governmen t departments and the masses. The monitoring andwarning system of the catastrophic sandstorm must be established or perfected as soon as poessible.