2012年初夏滇中首场暴雨过程诊断分析

Diagnostic Analysis on the First Summer Rainstorm Process of Central Yunnan in 2012

利用地面加密观测资料、多普勒天气雷达回波强度、卫星云图TBB资料和NCEP 1°×1°分析资料,应用滤波和广义位涡理论,对2012年6月1—2日云南省中部的首场切变冷锋型暴雨天气过程进行诊断分析。结果表明:中尺度天气系统是该次暴雨产生的直接原因,强降水均发生在云顶亮温等值线梯度较大一侧,回波强度空间分布不均匀,回波发展高度较低,但回波结构致密,低质心,以液态降水粒子为主,因此降水分布不均匀,但降水效率高;水汽源地为孟加拉湾;低层水汽通量辐合带与冷锋、切变线、中尺度辐合线以及β中尺度低涡位置有较好的对应关系;700 hPa,850 hPa水汽通量强辐合区中心位置叠加时,其所在区域地面降水增强;强降水区域上空中低层广义湿位涡的正异常现象体现了降水区中低层高水汽集中特征;单站上空低层的广义湿位涡正异常增加时,地面降水强度增加,反之减小;800 hPa广义湿位涡正异常区对地面降水分布有一定指示作用,但暴雨中心与广义湿位涡强中心并不完全重合。

Based on intensive observations, hourly FY-2E infrared TBB data, Doppler radar echo data and analy- sis data of NCEP （1°×1°,4 times a day）, the first rainstorm process in central Yunnan from 1 June to 2 June in 2012 are diagnostically analyzed using meso scale filtering method and generalized moist potential vortices theories （GMPV）. The result shows that this strong precipitation process is caused by cold front and sheer, which is typ- ical in central Yunnan. Shear line, mesoscale convergence line and meso-13-scale low vortex are significant at 700 hPa after mesoscale filtering, but they are not obvious in largescale original stream fields. So the di- rect causes for this rainstorm process are mesoscale weather systems. It seems apparent that the rainstorm always happens at the side which TBB gradient is higher in the convective cloud clusters by hourly FY-2E infrared TBB data. After analysis on Doppler radar echo data, there is a large area of flocculent echoes at the strong precipitation region, and then some convective clouds develop in these flocculent echoes. Distri- bution of rainfall is not uniform in space and the efficiency of rainfall is high because of uneven distribution of echoes in space, low height and dense structure of echoes. The source region of water vapor is the Bay of Bengal. The water vapor convergence zones have a good correlation with the position of surface cold front, shear line, mesoscale convergence line and meso-β-scale low vortex at 700 hPa. The ground precipi- tation strengthens when the center of vapor convergence area at 700 hPa and 850 hPa are superimposed. The positive anomaly of GMPV at mid-low layers over strong rainfall area can reflect characteristics of high water vapor convergence. Vertical distribution and change of GPMV at the low layer of single station show good indicative significance in this strong rainfall process. The rainfall is intensified when the posi- tive anomaly of GPMV at the low layer of single station increase, and vice versa. The GMPV at 800 hPa has an indicative effect on the location of heavy rainfall. The area of GPMV positive anomaly is always lo- cated in the center of strong precipitation and its surrounding area, but the center of strong precipitation is not coincided with the center of positive anomaly of GMPV completely. The forecast of this process will be better if the circulation patterns are analyzed synthetically, and the generalized moist potential vorticity theories are used as well.