常规资料揭示的中尺度对流复合体的环流结构

MESO α SCALE CIRCULATION OF MESOSCALE CONVECTIVE COMPLEX REVEALED BY CONVENTIONAL SOUNDING DATA

用常规地面和高空资料考察了发生在１９９２年７月２３—２４日的中尺度对流复合体（ＭＣＣ）的环流结构。涡度和散度场的客观分析清楚地展示出ＭＣＣ的中－α尺度环流。在对流层上部（３００ｈＰａ以上）是一个中尺度反气旋式辐散环流，在对流层下部（以７００ｈＰａ为中心）是一个气旋式辐合环流。这种环流结构是与ＭＣＣ的热力结构（对流层中高层的暧心和近地面的冷堆）相一致的。在５００ｈＰａ上没有发现北美ＭＣＣ所具有的中层涡旋。在地面上是一对正负涡度（北部为负南部为正）与ＭＣＣ相配合，而不是象北美ＭＣＣ中的地面中－高压和尾部低压。文中给出了ＭＣＣ环流的概念模式。

The circulation of MCC(Mesoscale Convective Complex) that occurred in 23 24 July 1992 are examined by conventional surface and upper air data. The objective analysis revealed distinctly the meso α scale circulations associated with the MCC on the vorticity and divergence fields. There are a mesoscale negative vorticity circulation with divergence in the upper troposphere ( above 250hPa) , and a positive vorticity circulation with convergence in the lower troposphere (centered at 700hPa). The major features of MCC structure are associated with the warm core in middle to upper troposphere and the cold air dome near the surface. No distinct midlevel cyclonic vortex is found at 500hPa. A couple of vorticity( negative in the northern portion and positive in the southern portion) was found on the surface instead of the meso high and the trailing cyclone which are found in northern America. The conceptual model of MCC circulation is presented.