“伊布都”台风影响云南的暴雨过程分析

Analyses of A Yunnan Rainstorm Process Influenced by the "Imbudo" Typhoon

利用Micaps常规资料,采用FY-2卫星红外增强云图及昆明CINRAD-CC雷达资料,分析了2003年7月25日20:00～26日20:00由于'伊布都'台风低压西行引发的云南暴雨过程.结果表明,由于副热带高压的西伸加强,其西侧持续强盛的低空偏南急流使西移到云南的热带低压维持并加强,在此有利的大尺度背景下,使云南境内的台风低压云系由MβCS发展为MαCS-MCC;通过K指数、θse特征、非地转湿Q矢量及非地转湿Q矢量散度等的分析,发现高能、高湿不稳定能量的积聚、低层的水汽辐合是此次暴雨过程的触发机制;地形的抬升导致低压发展,是暴雨产生的重要原因之一;多普勒雷达回波显示,台风低压有明显较大尺度的气旋式螺旋带状回波结构,并伴有多条强回波短带的出现及合并;在多普勒雷达速度图上,逆风区、气旋式辐合、大风区、持续的暖平流是造成本次暴雨过程直接的中小尺度天气系统.

Using the routine data of Micaps, FY-2 satellite infrared enhanced image and CINRAD-CC rada data, the rainstorm process in Yunnan province at 20：00 on 25-26 July 2003 caused by the Imbudo typhoon moving westward was analyzed. The result showed that because the westward extension and strengthning of subtropical high, the strong southerly low level jet on the west edge makes the moving westward tropical cyclones in Yunnan to maintain and strengthen and that the MβCS devolopes into MαCS- MCC within the typhoon low depression system in the boundaries of Yunnan province under the favorable large-scale background. It is found that the unstable energy accumulation and water vapour convergence in the lower layer of troposphere are a trigger mechanism of this rainstorm by index K, θsc, ageostrophic wet Q-vector and ageostrophic wet Q-vector divergence. The orographic lifting leads to the developing of typhoon low pressure, which is one of the import reasons of this heavy rainstorm. Dopplar rada echo showed that there was obvious cyclonic spiral band echo on large-scale and it combines with the several short strong echo bands. In Doppler rada speed picture, the anti-wind zone, cyclonic convergence zone, gale zone and durative warm advection are the direct synoptic systems of causing this rainstorm.