2024年2月我国两次雨雪冰冻过程中闪电活动特征对比分析

Comparative analysis of lightning activity characteristics during two rainfall/snowfall and freezing events in China in February 2024

2024年1月31日-2月5日和2月18-25日(以下分别简称为"0131"和0218"过程)我国南方遭遇两次雨雪冰冻天气,并伴随密集的闪电发生。利用三维闪电定位数据、CLDAS-V2.0降水产品和Himawari-9号卫星红外云图资料,对比分析两次雨雪冰冻天气背景下的地闪时空分布、地闪回击数和雷电流累计概率分布特征,并研究了地闪与降水量及卫星黑体辐射亮温(TBB)间的关系。结果表明:(1)两次过程中共监测到地闪数13万余次,正、负地闪分别为2万和11万余次;两次过程的地闪均具有夜发性,正地闪较总地闪和负地闪峰值滞后约1~2h。两次过程中正地闪产生大电流的概率大于负地闪。(2)"0131"过程中地闪密度大值区出现在贵州南部及贵州、重庆、湖北三省交界处;"0218"过程中地闪密度大值区出现在湖北东部、江西北部、安徽、江苏和浙江大部。(3)"0131"过程中降水量和地闪的时空分布不一致,降水量峰值集中在白天,降水集中在湖南东南部、江西、安徽和江苏南部、浙江和福建大部;而"0218"过程中降水量和地闪的时空分布较一致,地闪出现的峰值较降水量峰值延迟2h。(4)两次过程中地闪的分布均很好地指示了对流区。地闪主要分布在对流云团发展方向的尾部且偏南处TBB变化梯度大的区域;对流合并会导致合并处地闪频数的跃增;对流发展最旺盛的冷云核心区几乎没有地闪发生。两次过程地闪密度随着TBB的增大呈现先增大后减小的变化特征。

Southern China encountered two rounds of rainfall/snowfall and freezing weather accompanied by intensive lightning flashes from January 31 to February 5 and February 18-25,2024(hereinafter referred to as"0131"and"0218"events,respectively).In this paper,three-dimensional lightning location data,CLDAS-V2.0 precipitation product,and infrared cloud image data of Himawari-9 satellite are used to analyze and compare the temporal and spatial distribution of cloud-to-ground(CG)flashes,the number of return strokes and the cumulative probability distribution of lightning current during these two events.The relationship between CG flashes with precipitation and satellite blackbody brightness temperature(TBB)is also investigated.The results are as follows.(1)More than 130,000 CG lightning flashes were detected in the two events,with positive and negative CG lightning strokes being more than 20,000 and 110,000,respectively.The CG flashes of the two events showed a nocturnal pattern,with the peak of the positive CG distribution lagging behind the total CG flashes and negative CG flashes by about 1-2 h.The probability of large current events generated by positive CG flashes was greater than that of negative CG flashes.(2)In the"0131"event,the large value of CG flash density appeared in the southern part of Guizhou and the junction of Guizhou,Chongqing,and Hubei provinces;In the"0218"event,the large value of CG density occurred in the eastern part of Hubei,the northern part of Jiangxi,Anhui,Jiangsu and most of Zhejiang.(3)The spatial and temporal distribution of precipitation and CG flashes during the"0131"event was inconsistent.The peak precipitation was concentrated in the daytime,with the precipitation mainly appearing in southeastern Hunan,Jiangxi,Anhui,and southern Jiangsu,and most of Zhejiang and Fujian.During the"0218"event,the spatial and temporal distribution of precipitation and CG flashes were consistent,with the peak of CG flashes being 2 h later than the peak of precipitation.(4)In both events,the distribution of CG flashes well indicated the convection regions.The CG flashes were mainly distributed in the southern tail of the convective cloud cluster,where the TBB gradient was large.Convective merging may lead to a jump in the frequency of CG flashes at the merging area.Almost no CG flashes were detected in the core of the cold clouds,where convection developed most vigorously.The CG flash density in both events increased first and then decreased with the increase of TBB.