关键词: 西北地区, 黑风暴, 成因与对策

Abstract: By analysing the thirty-year(1951-1980)climatological data and the catastrophic sandstorm case which happened in Northwest China on 5 may 1993.the analytical results were concluded 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 sandstorm occurring in April was the highest in the whole year.The frequency of the sandstorm happenning in spring was nearly a half of that in the whole year.(2)There are three causes which lead to sandstorm mainly happenning in Northwest China in spring season. First, weather is arid and the soil is porous.second, the position of subtropical jet stream is advantageous to frequently forming strong wind. Finally,the convective activity resulting from the unstability of the atmosphere is beneficial to the drop-transmission of the momentum from the jet stream.(3)The large-range sandstorm and local catastrophic sandstorm occurring on 5 May 1993 were due to the passages of the strong cold front.The low-pressure system in the northeast of the Qinghai-Xizang Plateau,the low-level easterly jet over Gansu Hexi Orridor and meso-scale squall line also played 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 about catastrophic sand storm for the local government departments and the masses. The monitoring and warning system of the catastrophic sandstorm must be established or perfected as soon as possible.

Key words: Northwest China, Catastrophic sandstorm, Formative causes and countermeasures