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

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.