一次槽后“湿”对流风暴的中尺度分析

Mesoscale Analyses on A Moist Convective Storm Rain Behind Trough

对2002年8月5日发生在陕西境内一次槽后'湿'对流风暴过程进行了中尺度分析,结果表明:500 hPa槽后冷平流是这次过程的直接影响系统;850 hPa能量锋区和高能区提供了能量和强位势不稳定区;南海'北冕'台风和高原东侧副热带高压为此次过程提供了充沛的水汽,中、低空水汽通量超常;高、低空急流耦合产生的次级环流提供了持续强劲的上升运动;地面中尺度涡旋发展、合并及扩散是次级环流部分上升支演变过程的具体反映;产生强对流风暴的块状回波强度为45～55 dBz,高度为12～14 km.

Mesoscale analyses were carried out for a moist convective storm rain behind trough in Shaanxi Province on August 5, 2002. The primary results are as follows:This heavy storm rain was of long-time duration, wide influence and high density, which reflected the synoptic feature of moist convection storm rain. The southward movement of cold advection behind 500 hPa trough was direct factor of this process; %θ%-(se) on 850 hPa, frontal zone in the northern part, and energy zone in the mid- and south- parts supplied the energy and caused strong unstablezone of potential for this process. Typhoon named “kammuri”located in the South China Sea, transformed water moistureto the continent, and provided the ample moisture for this process. Moist in the whole atmosphericlayer, moist and cold in the upper, caused the moist convection wind storm; second-circulationformed by couplingof high- middle and low-level jets resulted in successive violentupdraft. Evere rainfall weather in the northern part of shannxi was caused by one of the two mesoscale cyclones, and short-term storm rainfall and heavy storm rain in the middle and southern parts were caused by amalgamationof two mesoscale cyclones. Effect of sub-circulationmight be main reason of surface mesoscale cyclone. Thedensity of radar echo appeared in pieces for this process varied from 45 to 55 dBz, and its cloud height reached to 12~14 km, the maximum was 16 km.