摘要
为提高中国西南复杂地形区域雹暴预报水平,对该区域内一次典型雹暴过程中的地形作用、微物理过程及成雹机制进行系统分析,并采用全弹性三维对流云模式进行数值模拟.结果表明:(1)雹暴过程为冷空气侵入型,地形对低层暖湿气流的阻拦导致水汽的积累,同时高原槽引导的冷空气触发雹暴.(2)近地面层或500～300 hPa高度层的>8×10-5/s的涡度中心、750 hPa高度存在散度<-8×10-5/s的辐合中心且在500 hPa或以上层次转为辐散、近地面层水汽通量散度<-12×10-8g/(s·cm2·hPa)、假相当位温梯度>4 K/km、0～6 km垂直风切变>15 m/s这几个阈值可以为西南复杂地形区域的雹暴过程提供预警.(3)32.03 m/s的强垂直风切变和旋转速度达19.85 m/s、厚度超3km的强中气旋是降雹单体的主要维持机制.(4)雹胚主要由雪晶撞冻过冷雨滴产生,低密度霰在沉降过程中凇附云水和过冷雨滴增长成雹是主要的成雹机制.对贵州地区雹暴过程的预报具有一定指导作用.
Abstract
To improve the forecasting level of hailstorms in the southwestern complex terrain region of China,this paper systematically analyzes the terrain effect,microphysical process,and the mechanism of hail formation during a typical hailstorm in the southwestern complex terrain region of China,and numerically simulates it by using the fully elastic three-dimensional convective cloud model.The results show that:(1)this hailstorm process is a cold air intrusion type hailstorm,and the terrain's obstruction of the low-level warm and humid airflow led to the accumulation of water vapor,while the cold air guided by the plateau trough triggered this hailstorm.(2)The existence of vorticity centers greater than 8×10-5/s in the near-surface layer or 500～300 hPa altitude layer,the existence of convergence centers with dispersion less than-8×10-5/s at 750 hPa altitude and turning into convergence dispersion at the level of 500 hPa or above,the near-surface water vapor flux dispersion greater than-12×10-8,the pseudo-equivalent temperature gradient greater than 4 K/km,and the vertical windshear greater than 15 m/s at the 0-6 km altitude are some of the thresholds that can pro-vide early warnings for the hailstorms in the southwestern region of the complex terrain.(3)The strong vertical wind shear of 32.03 m/s and the strong medium cyclone with a rotational speed of 19.85 m/s and a thickness of more than 3 km are the main maintenance mechanisms of the hail monomer.(4)Hail embryos are mainly produced by snow crys-tals hitting frozen supercooled raindrops,and low-density shrapnel is the main hail formation mechanism in the process of precipitation of freezing attached cloud water and supercooled raindrops to grow into hail.The results of the study have a certain guiding effect on the forecasting of hailstorm processes in Guizhouand analyze the topographic effects.
维普
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