贵州罕见冬季强冰雹过程分析和数值模拟研究

Analysis and CMA-MESO Numerical Simulation of a Rare Winter Heavy Hailstorm in Guizhou

  • 摘要: 本文利用多源气象观测资料和ERA5再分析资料,并结合CMA-MESO高分辨率数值模拟结果,分析了影响2024年初罕见冬季冰雹过程的主要天气系统及其时空演变和三维结构特征,发现2024年1月1日08时—2日08时(北京时,下同)贵州区域降水实况分为2个阶段(1日19:00—2日00:00贵州中部以西以南冰雹为主的对流活动和2日00:00—08:00贵州中部以东以南降水为主的对流活动),并重点针对第1阶段冰雹过程开展研究。结果表明:(1)在冰雹过程发生前(1月1日14:00和18:00),云南东部及贵州西部有热低压发展,其热效应加强了贵州中部以西以南地区地面辐合和不稳定能量积聚。(2)在高低空环流场配置上,对流层高层辐散、中层高空短波槽东移扰动、中低层较明显的偏南暖湿气流及暖式切变,以及高低空干湿区叠加的共同影响,为冰雹过程提供了有利的动力、水汽和不稳定层结条件,地面静止锋的稳定维持是冰雹过程的主要天气尺度系统,为过程提供了触发条件,而地面锋前的上升运动与高空急流出口区的上升气流相叠加,对冰雹过程的发生发展起到了增强作用。(3)在21:30前后时段,长顺县发生了最强冰雹过程,飑线强回波单体活动也达到高峰,在对流层中低层形成回波悬垂结构,在低0 ℃层和−20 ℃层的背景下,强烈的上升气流循环托举雹胚,使得其表面不断凝结过冷水珠,为大冰雹的形成提供了必要条件。(4)CMA-MESO高分辨率数值模式一方面清晰地揭示了长顺县大冰雹发生发展时,由于中高层冷空气的侵入,在最强上升速度区域形成了显著的θse锋区,不仅增加了大气的不稳定度,也为对流天气的发生提供了触发机制;另一方面,通过高分辨率的探空曲线模拟,揭示出大冰雹发生前CAPE高值持续释放、风垂直切变持续增强、低层暖平流持续加强和中高层冷空气干入侵由强到弱的环境场变化对降雹区预报具有较好的指示意义。

     

    Abstract: Using multi-source meteorological observation data and ERA5 reanalysis data, combined with CMA-MESO high-resolution numerical simulation results, the main weather systems, spatio-temporal evolution and three-dimensional structure characteristics affecting the process of rare winter hail in 2024 are analyzed in detail. There were two precipitation stages from 08:00 on January 1st to 08:00 on January 2nd. From 19:00 on January 1st to 00:00 on January 2nd, the hail was the main convective activity in the west and south of the central part of Guizhou. From 00:00 to 08:00 on January 2nd, the precipitation was the main convective activity in the east and south of the central part of Guizhou. The research object was the first stage. The results indicate: (1) Before the hail process occurred (14:00 and 18:00 on January 1st), there was a thermal low pressure development in eastern Yunnan and western Guizhou, whose thermal effect strengthened the ground convergence and the accumulation of unstable energy in the west and south of the central part of Guizhou. (2) In terms of the configuration of high and low circulation field in the troposphere, the divergence in the upper troposphere, the eastward disturbance of the short-wave trough in the middle troposphere, the obvious southerly warm and wet airflow and warm shear in the middle and lower troposphere, as well as the superposition of the dry and wet regions in the middle and lower layers provided favorable dynamic, water vapor and unstable stratification background conditions for the hail process. The stable maintenance of the ground stationary front was the main synoptic scale system for the hail process, providing triggering conditions for this process. The upward motion of the surface prefrontal overlapped with the updraft of upper-level westerly jet, which enhanced the occurrence and development of the hail process. (3) The strongest hail process occurred in Changshun around 21:30, which companied with the peak activity of the strong echo cell activity of the squall line, forming an echo overhanging structure in the middle and lower troposphere. Under the background of the lower 0℃ layer and −20 ℃ layer, strong updraft circulated to lift the hail embryo, making the surface of the hail condensation continuously, providing the necessary conditions for the formation of heavy hail. (4) The CMA-MESO high-resolution numerical model clearly revealed that during the occurrence and development of heavy hail process in Changshun, a significant θse front region was formed in the region of the strongest rising velocity due to the intrusion of cold air in the mid-upper troposphere, which not only increased the instability of the atmosphere, but also provided a triggering mechanism for the occurrence of convective weather. The change characteristics of environmental field, which included the high CAPE value was released continuously, wind vertical shear was strengthened continuously, warm advection was strengthened continuously in the lower troposphere, and the dry invasion of cold air was from strong to weak in the mid-upper troposphere, had good indicative significance for the prediction of hail region.

     

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