Characteristic Analysis of Mesoscale Convective System of Heavy Rainstorm in Kunming in the Late Spring 2012
Based on conventional meteorological observational data, NCEP/NCAR 1°×1° 6 h reanalysis data, the blackbody temperature of FY2E satellite infrared images, Cband Doppler radar sounding data and simulation results with mesoscale numerical model, a locally heavy rainstorm that occurred in the evening of 24 May 2012 is studied. For the mesoscale convective systems, the evolution characteristics and their formation mechanisms are analyzed in detail. The results show that the best configuration of upper and low layer systems made the generation of heavy rainstorm. As the peak of precipitation appeared, the lower layer became warmer and wetter, significantly convectionalunstable stratification from surface to 500 hPa appeared, and vertical wind shear reached 14 m·s-1 in 700-500 hPa. In zonal structure, easterly enhanced at lower layer in the rainstorm center, zonal wind convergenced under 300 hPa, and its center intensity was -28×10-5 s-1, center intensity of updraft under 150 hPa was 21 m·s-1, convergence of moisture flux near surface was -20×10-5 g·hPa-1·s-1·cm-2. In meridional direction, southerly speed convergenced under 500 hPa in the rainstorm center, then updraft enhanced. Meridional strength was the same as those in zonal direction. Convergence intensity of moisture flux at lower layer was -30×10-5 g·hPa-1·s-1·cm-2, 〖JP2〗stronger than that of zonal intensity. In addition, 〖JP〗topographic forcing affected south wind significantly, and the lifting speed was 0.4-1.0 m·s-1. Moreover, heavy rainfalls were different in the four stages, namely, initial, enhancement, fallback and attenuation. While cold air in surface layer over Kunming enhanced, convective cell on its east side moved to Kunming, then heavy rainfall generated. Thereafter, southerly wind pulsated, local wet layer was thickened, vertical wind shear increased, convective cell enhanced twice, and precipitation peak appeared. The formation of the third precipitation peak was mainly caused by southerly wind pulsating and convective cell complicating, but because volume of incorporation cell was smaller than that of local cell, precipitation peak created by the local cell was obvious smaller than the peaks in the previous ones. Convective precipitation echo belonged to warm cloud property and had tropics low centroid characteristic.