Diagnostic Analysis of a Heavy Rainfall in Southern Sichuan of China Induced by Southwest Vortex
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摘要: 利用NCEP/NCAR1°×1°格点再分析资料，对2007年7月8─10日发生在川南地区的西南低涡暴雨做了一次较为全面的诊断分析，结果表明：（1）500hPa高度场上小槽与700hPa西南低涡缓慢东移；流场上有低层辐合高层辐散的结构；垂直速度场上维持有较强烈的上升运动；这些都为暴雨的发展和维持提供了有利的条件。（2）对流层低层假相当位温随高度降低，有不稳定能量的存在，易于触发暴雨。（3）湿位涡分析得出，MPV1垂直结构呈正负值叠加的配置是暴雨发生发展的有利形势，强降水落区基本位于MPV1正负值交界的等值线密集带；MPV2的增大可使对流运动和降水加强。Abstract: Using NCEP data of 1°×1°with 6-hour interval, the evolution of Southwest Vortex (SW) causing heavy rainfall in Southern Sichuan of China during 8-10 July 2007 is comprehensive diagnosis. The results indicate that: (1) On height field, there is a small groove on 500hPa, and 700hPa southwest vortex moving eastward slowly; on fow field; there is a structure of convergence on the low level and divergence on the upper level; on vertical velocity field, there maintains a relatively strong upward motion, they provide a favorable circulation background for the development and maintenance of heavy rainfall. (2) On the lower troposphere, the pseudo-equivalent temperature decreases with height. The existence of an unstable energy can easily trigger heavy rainfall. (3) Moist potential vorticity analysis gives a superposition of the vertical structure of the configuration, both positive and negative, to provide a favorable situation in the development of heavy rainfall. Strong precipitation areas are basically located in the dense band contour of the positive and negative junction of MPV1; the increase of MPV2 is conducive to the intensification of convection and rain.
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Keywords:
- southwest vortex /
- heavy rainfall /
- diagnosis /
- moist potential vorticity
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