中国南方地区夏季地闪和降水协同变化的特征及气象要素分析

Co-Variability Between the Summer Cloud-to-Ground Lightning and Precipitation over South China and Their Possible Connections with Meteorological Parameters

关键词:  地闪  降水  协同变化  自组织映射网络  气象要素

Key words:  cloud-to-ground lightning  precipitation  co-variability  self-organizing map  meteorological parameters

摘要:

利用 ADTD地闪定位数据和地基-卫星-雷达融合降水数据，通过耦合自组织映射网络(SOM)的聚类方法，分析了 2016—2021 年中国夏季地闪和降水协同变化的时空分布特征。研究区域位于我国南方地区(105～122 °E，20～35 °N范围内)，覆盖了地闪密度和降水气候态的大值区。聚类结果显示我国地闪-降水耦合分布型可归为 5 类，其中第一类和第五类中地闪密度和降水异常的协同变化最一致。第一类表现为江淮地区降水-地闪活动偏多且华南地区降水-地闪活动偏少的偶极型分布，第五类与其分布相似，但符号相反。不同类型的地闪-降水耦合分布型对应着不同的地闪密度和降水异常中心，并且地闪密度和降水关系呈现出明显的地域差异性、非线性和非对称性。进一步研究发现，不稳定的大气层结、显著的中低层湿度差和有利的大尺度大气环流背景场是造成我国南方地区地闪-降水协同变化的重要因素。

Abstract:

The co-variability in the summer precipitation and cloud-to-ground lightning over South China, where climatological lighting and precipitation frequently occur (105～122 ° E, 20～35 ° N), has been examined using the ADTD lightning location network and precipitation data merged ground-gauge, satellite, and radar. The coupling self-organizing map (SOM) has been applied to the daily flash density and precipitation anomalies from 2016 to 2021. It turns out that there are five clusters associate with the co-variability in the flash density and precipitation over South China. Specifically, the first (fifth) cluster is characterized by a dipole pattern with enhanced rainfall/increased lightning activity (suppressed rainfall/ decreased lightning activity) over the Yangtze-Huai River valley and suppressed rainfall/decreased lightning activity (enhanced rainfall/increased lightning activity) over the southern part of South China. The tightest lightning-precipitation coincidence is observed in the first and fifth clusters. Results obtained from SOM exhibit large non-linearity and asymmetry of the relationship between the regional lightning and precipitation anomalies over South China. Further examinations suggest that unstable atmospheric stratifications, significant vertical differences in the atmospheric humidity, and beneficial large-scale atmospheric circulations play important roles in modulating the co-variability in the summer lightning and precipitation over South China.