利用常规气象观测资料、6.7 μm卫星水汽图像和TBB、闪电定位资料以及NCEP/NCAR 1°×1°再分析资料, 对2009年3月3日南方地区一次高架雷暴天气过程进行诊断研究。结果表明, 该过程主要影响系统是中低层低槽、低涡切变线、西南低空急流、南北支西风急流。低空急流造成暖湿气流输送和高空急流造成冷平流侵入是对流触发机制。近地层为层结稳定的"冷空气垫", 位势不稳定出现在低空急流与中高层干冷气流之间, 并因急流中的下沉运动得以加强; 西南暖湿气流与其北部干冷气流在中低层形成湿斜压锋区, 西南气流的下沉支和北方下沉气流汇合在近地层形成的东北风回流与上部西南风生成锋面次级环流圈及中高层上升气流与北支急流中的下沉气流耦合形成次级正环流圈有利于倾斜上升运动的发展; 低空急流的强暖平流和水汽通量辐合、北支急流入口区右侧的强辐散和南支急流北侧的辐合均加强了中尺度上升运动。湿层浅薄、上下干层较为深厚、强垂直风切变、低层逆温、-20~0℃过冷水层气流强上升运动等有利于雷暴天气的发生。雷电和冰雹出现在TBB、低空急流风速、θse、水汽通量以及300 hPa散度等值线密集区附近。
An elevated thunderstorm process in southern China on 3 March 2009 is analyzed by using conventional observation, 6.7 μm satellite vapor images and TBB, lighting location and NCEP/NCAR reanalysis. The main synoptic systems include trough at middle-low levels, vortex and shear line, low-level jet, upper-level southern and northern western jet. The storm is triggered by low-level jet warm water vapor transportation and invading of high-level cold air. The boundary is dynamically stable for the existence of a thick cold pad. Convection instability appears between low-level warm and humid southwest jet and the cold and dry air at middle and high levels, and strengthened by the descending motion of the upper jet. A strong baro-clinic frontal zone is formed by the meeting of southwest jet and the cold and dry air northward at low-middle levels. The confluence of the southwest air descending branch and the cold and dry air from northern area causes northeast backflow which couples with the southwest winds above the boundary and forms a secondary front circulation, the ascending air at middle-upper levels couples with descending air of northern westerly jet causes another secondary positive circulation, the two northward titling secondary circulations are very favorable for tilting ascending movement. The warm advection and water vapor flux convergence of low-level jet, the strong divergence at the right entrance of upper-level western jet and the convergence along the southern upper-level jet are also contributable for meso-scale ascending movement. Thunders and hails appear usually at the dense band of θse, low-level jet speeds, water vapor flux and 300 hPa divergence. In addition, the environmental conditions as the thin humid layer, strong wind shear, low-level temperature inversion, ascending motion at -20~0℃ super cooled water layer are very advantageous to thunderstorms.
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