贵州威宁雹暴微物理特征的观测及数值模拟研究

STUDY ON OBSERVATION AND NUMERICAL SIMULATION OF MICROPHYSICAL CHARACTERISTICS OF HAILSTORM IN WEINING COUNTY, GUIZHOU PROVINCE

关键词:  双偏振  粒子识别  WRF数值模拟  雹  云微物理机制

Key words:  dual-polarization  particle identification  WRF numerical simulation  hail  cloud microphysics mechanism

摘要:

利用位于贵州威宁雪山镇的X波段双偏振雷达，在观测资料质量控制的基础上，结合基于模糊逻辑的水凝物粒子识别算法(HID)以及中尺度数值模式WRF，对2018年6月28日贵州威宁羊街镇的一次强雹暴天气过程进行分析。结果表明：此次冰雹过程，观测识别与模式模拟结果具有较好的一致性，主要经历发展、成熟(孕育)、成熟(降雹)、衰减(消亡)四个阶段。(1) 发展阶段：低密度霰(LDG)初生于-20 ℃层附近(5.0~6.8 km)，是冰晶(CR)与周围过冷云水的凇附作用所致；高密度霰(HDG)初生于2.6~4.2 km， 由聚合物(AG)凇附周围过冷云水所形成。(2) 成熟(孕育)阶段： LDG、HDG以AG粒子为主要霰胚源进行凇附增长； 雨夹雹(RH)初始形成在[-20 ℃]层附近(4.2~6.8 km)，由周围少量HDG为雹胚源碰冻过冷云水所致。(3) 成熟(降雹)阶段：LDG通过碰并作用大量形成，HDG产生有两种源项，一是由AG粒子(3.4~6.0 km)为高密度霰胚源的凇附作用，二是由上方的LDG粒子(6.8~9.3 km)，因重力沉降作用，在下沉中撞冻过冷水所形成，并最终由HDG为主要雹胚源形成RH。(4)衰减(消亡)阶段：在0 ℃层附近(3.4 km)，零星HDG撞冻过冷雨水(RN)保持缓慢增长，继续下沉的LDG、HDG因融化作用明显，逐步转变为液态降水。

Abstract:

Based on the quality control of observational data, the heavy hailstorm that occurred in Yangjie Town, Weining County, Guizhou Province on June 28, 2018 is analyzed. The study combines a fuzzy logic hydrometeor identification algorithm with the mesoscale numerical model WRF and uses the X-band dual-polarization radar located in Xueshan Town, Weining County, Guizhou Province. The results show that there is a good consistency between the observation and model simulation results of this hail process, which mainly goes through four stages: development, ripeness (hail formation), ripeness (hail shooting) and attenuation (disappearance). (1) Development: Caused by the riming between ice crystals and surrounding super-cooled cloud water, low-density graupel (LDG) is formed near the cloud layer of -20 ℃ (5.0~6.8 km). Caused by the riming between aggregation (AG) and surrounding super-cooled cloud water, high-density graupel (HDG) is formed near the cloud layer with a terrain clearance of 2.6~4.2 km. (2) Ripeness (formation): AG is the main source of graupel embryo for LDG and HDG. The rain mixed with hail (RH) is initially formed near the cloud layer of -20 ℃ (4.2~6.8 km) and it is caused by a small amount of HDG which collides with and freezes the super-cooled cloud water. (3) Ripeness (hail shooting): LDG is largely formed by coagulation. HDG develops from two sources: one is the riming with the AG particles (3.4 ~ 6.0 km) as the HDG embryo source, and the other is the gravity sedimentation by the top LDG particles (6.8 ~ 9.3 km), in which the particles develop into a large amount of HDG through coagulation with other ice phase particles during sedimentation. Finally, the HDG develops into the RH. (4) Attenuation (disappearance): HDG grows slowly by colliding with the super-cooled cloud water near the cloud layer of 0 ℃ (3.4 km). While falling continuously, LDG and HDG are gradually converted into liquid precipitation due to obvious melting effect.