江西一次特大暴雨中尺度对流系统特征对比分析

Comparative Analysis of Mesoscale Characteristics between Two MCSs of A Torrectial Rain in Jiangxi Province

利用FY-2E云顶亮温(TBB)资料,雷达回波资料以及非静力中尺度数值预报模式WRF的模拟结果,对比分析了2010年6月19日江西特大暴雨过程中TBB低值接近但地面降水量差异显著的两个中尺度对流系统(MCS)。结果表明:MCS1为新生对流在有利的水汽、动力和热力条件下迅速发展形成的强盛中尺度对流系统,中低层辐合高层辐散、气旋性涡旋发展旺盛,对流云柱内强上升运动将辐合的大量低层水汽输送至中高层,云水、云冰含量增加,两者重叠层加厚,水物质总量增加,造成地面出现强降水;MCS2尾随层云区的弱辐合仅出现在中层,水汽辐合量和液态水物质含量显著偏小,对应地面弱降水,但是由于高层云冰含量与MCS1对流云区相当,高层雷达回波强度相当,导致卫星云图上TBB出现与MCS1相同的低值。

Using of the satellite TBB data,Doppler radar data,and the results of WRF mesoscale non-hydrostatic model,compared the characteristics of two mesoscale convective systems（MCS） with similar Black Body Temperature（TBB） value but quite different surface precipitation in the heavy rainfall in Jiangxi province on 19 June2010.The results showed that in beneficial water vapor,dynamic and thermal conditions,newborn convective cell grows to strong mesoscale convective system（MCS1）.Wind field present convergent in the middle and lower layer and divergent in the higher layer.Cyclonic vortex develops from ground surface to 150 hPa.Plenty water vapor is transported to mid-high layer in the troposphere by vertical upward motion in convective cloud column,causing content of liquid cloud water and cloud ice increased and overlap layer of them deepened.Then total water substances content increase,causing low TBB value and heavy surface rainfall.Weak convergence in middle layer cause the content of water vapor convergence and total liquid water substances of MCS2 are significantly less than MCS1,so only weak surface rainfall occur.But in high troposphere,the cloud ice content and radar reflectivity in tailing stratus cloud of MCS2 is similar to the cloud ice content and radar reflectivity in convective cloud of MCS1 respectively,so the satellite TBB value of MCS2 is similar to MCS1.