西南低涡与不同系统相互作用形成暴雨的异同特征分析

利用1°×1°NCEP再分析资料和地面加密自动站资料，通过对2007年四川盆地盛夏3次西南低涡与不同系统相互作用时形成四川盆地暴雨过程的环流特征、影响系统以及风暴相对螺旋度、湿位涡、水汽通量等物理量场特征进行对比分析，找出西南低涡与不同系统相互作用形成暴雨过程中各物理量的异同点。分析表明，西南低涡与不同系统相互作用形成暴雨机制的共同点是：暴雨发生在西南低涡中心附近，西南低涡暴雨区内存在着稳定的上升气流和水汽辐合，伴有明显的能量释放特征，西南低涡暴雨都是发生在对流层中层螺旋度大值区，强降水一般出现在对流层低层MPV1〈0同时MPV2≥0的范围内，都具有“低层正涡度辐合，高层负涡度辐散”的典型暴雨动力结构。西南低涡与不同系统相互作用形成暴雨机制的不同点是：在西南低涡与高原低涡形成暴雨机制中高空急流的作用十分重要，在西南低涡与切变线形成暴雨机制中低空急流的动力作用十分明显，而深厚的西南低涡暴雨高低空急流作用不是十分重要。在西南低涡与切变线或深厚的西南低涡形成暴雨机制中锋面抬升作用明显，对流层高层MPV1正值区叠加在低层MPV1负值中心上，而与高原低涡相配合形成暴雨机制中锋面抬升作用不明显，不具有MPV1下负上正的结构。深厚的西南低涡暴雨是非移动的，而西南低涡与高原低涡或切变线形成的暴雨是移动性的。

Comparison and Analysis of the Similarities and Differences of Southwestern Low Vortex Interaction with Different Systems Causing Heavy Rainfall in Sichuan Basin

Based on the 1°×1°NCEP reanalysis data and automatic weather stations data, comparison and analysis of the similarities and differences of circulation pattern, influential system, storm relative helieity , moist potential vorticity and water vapor flux of three times heavy rainfall that produced by SW vortex interaction with the different systems in Sichuan Basin in jul of 2007. Identify the physical differences and similarities of the three times heavy rain. Analysis showed that the SW vortex interaction with the different systems produced heavy rain have some similar points： heavy rain occurred in the near the center of the SW vortex, there is stability increased airflow and water vapor convergence in the region of SW vortex rainstorm, with clear energy release characteristics. SW vortex rainstorm general occurred in storm relative helicity is positive large value areas, and the lower troposphere MPV1 〈 0 at the same time in the higher troposphere MPV2 ≥ 0, to have a ＂low - level positive vortieity convergence, high- level negative vortieity divergence ＂dynamic structure of typical rainstorm. SW vortex interaction with the different systems produced heavy rain have some different points ： the role of high - level jet is very important in the SW vortex and plateau vortex produced heavy rain. the low - level jet dynamic action is obvious in the SW vortex and shear line produced heavy rain, while high - level and low - level jets are not important in the deep SW vortex rainstorm. Front uplift apparently in the mechanism of SW vortex and shear line or deep SW vortex produced rainstorm, and MPV1 positive area in high -level trop- osphere superimposed on MPV1 negative center in low - level troposphere . But the action of front uplift was not obvious in the rainstorm that SW vortex interact with the plateau vortex, and is not MPV1 positive area in high - level troposphere and nega- tive area in low - level troposphere structure. SW vortex heavy rain is non - moving, the SW vortex interaction with platea