伊犁地区一次罕见特大暴雨中尺度系统的数值模拟

Numerical Simulation of Mesoscale System During a Rare Torrential Rainstorm Process in Yili of Xinjiang

利用自动气象站观测资料、FY-2G卫星TBB资料和NCEP/NCAR再分析资料,针对2016年6月16-17日伊犁地区的一次罕见强降水过程,在天气形势和中尺度系统分析基础上,借助WRF模式高分辨率模拟资料对强降水的形成过程进行细致分析。结果表明:中亚低槽、高空偏西急流、低空切变线和辐合线是此次强降水过程的主要天气系统。多个中尺度云团受伊犁北部天山地形抬升作用,长时间维持在沿天山地区,并持续产生强降水。模拟结果显示,不断移至北部沿天山地区的中尺度对流单体是造成此次伊犁地区强降水的直接中尺度系统,其发生发展与低空急流、低层风场辐合和地形有密切关系。低空急流增强引起动力辐合增强,触发不稳定能量释放,加之地形抬升,使得垂直运动维持并快速发展,并在有利的水汽条件配合下引发低层辐合线附近对流系统加强,导致伊犁北部沿天山地区出现强降水。

Based on conventional ground observation data, TBB data of FY-2 G satellite and NCEP/NCAR reanalysis data, the synoptic circulation pattern and mesoscale systems of the heavy rainstorm in Yili area of Xinjiang from 16 to 17 June 2016 were analyzed. And on this basis, the formation of the heavy rainstorm was analyzed in detail by using the output data of WRF model with high resolution. The results show that the main weather systems of the heavy rainstorm process were low trough in Central Asia, westerly jet in upper level, shear lines and convergence lines in lower layer. The multiple mesoscale cloud clusters sustained in Tianshan mountains area of northern Yili for a long time under the effect of terrain lifting, which caused strong rainfall continuously. The simulation result showed that the mesoscale convective cells moving continuously to the Tianshan mountains in northern Yili directly caused the heavy rainfall in Yili region, and the development of convective cells was closely related with low-level jets, low-level wind convergence and terrain. The dynamic convergence enhanced with increase of low-level jets, which triggered the release of CAPE(convective available potential energy), further led to the maintenance and rapid development of vertical motion together with terrain uplift, and caused the enhancement of convective system near convergence line in lower level, which were beneficial to the occurrence of heavy rainfall along Tianshan mountain of northern Yili.