中国西北地区1993年5月5日黑风暴的机理探讨

A STUDY OF THE PHYSICAL MECHANISM FOR A BLACK STORM IN NORTHWEST CHINA

该文用天气学、诊断分析方法对１９９３年５月５日我国西部地区黑风暴天气过程的发生发展及形成机理进行研究．结果表明，这次黑风暴是由强寒潮爆发，在特定季节（春季）和裸露、疏松的下垫面（沙漠、戈壁）条件下形成的中尺度现象．在对流层中低层垂直方向上存在很强的风切变，利于湍流发展；非地转强迫作用对次级环流贡献大于地转强迫作用；黑风暴前后显著的辐射加热不均匀分布所形成的热力正反馈作用，造成近地层局地锋生，并使热力正环流大大加强．

The physical mechanism of a black storm, which burst out in Northwest China on May 5, 1993, is studied using the methods of synoptic meteorology and diagnostic analysis. The results show that the black storm is a mesoscale phenomenon which forms and develops in particular season (spring) on the bare and loose underlying surface (desert, gobi) when a strong cold wave bursts out. The results also show that there exist strong wind shears in the vertical direction of middle and lower convective layer ; the wind shears are favourable to the development of turbulence; the contribution of the non-geostrophic forced function to the secondary circulation is greater than that of the geostrophic forced function. The positive thermodynamical feedback, resulting from the significant differential radiative heating before and after the appearance of the black storm, leads to the local frontogenesis of surface layer,and strengthens the positive thermodynamical circulation.