宁夏南部山区两次冰雹过程对比分析

Comparison of Two Hail Processes in the mountainous region of southern Ningxia

利用"葵花-8"卫星、多普勒雷达、常规气象观测和0.125°×0.125°ERA-Interim再分析资料,对2018年6月宁南山区午后发生的两次冰雹过程进行对比分析,旨在探明山区降雹及大冰雹生成的有利监测指标。结果表明":西高东低"形势下,高空急流配合中低层切变线和地面中尺度辐合线有利于冰雹天气的发生。当反射率因子≥60 dBZ、液态水含量≥35 kg/m2、回波顶高≥7 km,降雹概率为100%;中低层速度大值区持续存在时,降雹可能性很大。降雹易发生在云体发展强盛处及最大云顶亮温梯度前端,且亮温越低、亮温梯度和降温率越高时,降雹直径越大。同一地区,高层辐散越明显、近饱和层和高水汽含量层伸展越高、垂直风切变越大,对流云团发展将越旺盛,最强回波伸展高度将越高,降雹直径将越大。

To ascertain the favorable monitoring indicators of hail generation in the mountainous region,the comparison of two hail processes occurred in the afternoon of June 2018 in the mountainous region of southern Ningxia was analyzed,by using conventional observation,reanalysis data from ERAInterim,Himawari-8 satellite and doppler radar data. The results showed that the synoptic situation of"high in the east but low in the west",the upper-level jet stream accompanied with the shear line and the surface meso-scale convergence line were favorable for the occurrence of hail. The possibility of hail was 100% with the condition of the radar reflectivity factor of ≥60 dBZ,the vertical integrated liquid of≥ 35 kg·m-2,the echo top of ≥7 km. The probability of hail was high when the maximum radial wind in the middle and lower layers persisted. The hail was easy to occur in the region of cloud with strong developed and in front of the area with the largest brightness temperature gradient. When the cloud-top brightness temperature was lower but the gradient and the genting cooling rate were higher,the diameter of hail would be larger. For the same region,the development of convective cloud and the extension of the strongest radar echo would be promoted,and the larger hail would generate under conditions of the more obvious high-level divergence,the higher extension of nearly saturated and high moisture content layer,and the greater vertical wind shear.