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南疆西部两次短时强降水天气中尺度特征对比分析

Comparative analysis on mesoscale characteristics of two severe short-time precipitation events in the west of southern Xinjiang

  • 摘要: 利用常规气象探测、FY气象卫星、多普勒天气雷达、地面自动站资料以及NECP、EC高时空分辨率再分析资料,对比分析了2014年8月30日(简称“8.30”)和9月8日(简称“9.08”)南疆西部两次短时强降水天气中尺度特征。结果表明:“8.30”过程发生在高压脊前西北气流内,“9.08”过程出现在低涡底部平直西风带内,两次过程中地面和低空中尺度辐合线均是短时强降水的重要影响系统;造成短时强降水的β中尺度对流云团发展迅速、移动快,两次短时强降水分别产生在对流云团TBB梯度最大处和发展过程中范围最大时。两次过程在雷达回波特征方面存在明显差异,对流风暴质心高度明显不同,“8.30”过程影响系统为高质心γ中尺度超级单体,最强回波高度6 km,具有中低层辐合、高层辐散、旋转特征;“9.08”过程影响系统为低质心γ中尺度普通单体风暴,最强回波高度2 km,雷达径向速度上两次过程边界层辐合线对对流风暴的产生和加强有重要作用。

     

    Abstract: Based on data from conventional weather stations, Fengyun meteorological satellite, Doppler weather radar, automatic weather station, and NCEP and EC reanalyses with high time and spatial resolutions, mesoscale characteristics of two severe short-time precipitation events on 30 August (called "8.30") and 8 September 2014 (called "9.08") in the west of southern Xinjiang were analyzed. The results show that the "8.30" event took place in the northwest airstream ahead a high pressure ridge, while the "9.08" event appeared in a straight westerly belt in bottom of the vortex and trough. Mesoscale convergence lines at surface and low level were important influencing systems to the two severe short-time precipitation events. Short-time precipitation occured at the maximum gradient of TBB for the "8.30" event and maximum range for the "9.08" event. The two events had significant differences in radar echo characteristics and had obvious low and high quality heart convective storms. Severe short-time precipitation was caused by meso-γ supercell for the "8.30" event, its strongest echo height exceeded 6 km. So, it was a high quality heart convective storm and had the characteristics of low-level convergence, upper-level divergence and rotation. Severe short-time precipitation was caused by meso-γ common storm for the "9.08" event, and its strongest echo height exceeded 2 km, which was a low quality heart convective storm and low-level wind convergence. Radar velocity for the two events displayed that the boundary layer convergence lines played an important role in the generation and enhancement of convective storms.

     

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