Características das descargas nuvem-solo e da precipitação em superfície associadas a sistemas convectivos ocorridos na região sudeste do Brasil

Abstract

In this study, we investigated the relationship between cloud-to-ground (CG) lightning and surface precipitation produced by convective systems that occurred in October 2007, in southeastern Brazil. For this, we used data from the network RINDAT (Integrated Network National Lightning Detection) and automatic surface weather stations, linked to INMET (National Institute of Meteorology). Through the application of selection criteria, 18 convective systems were analyzed, of which six were in the details. To quantify the CG lightning generated by each convective system, satellite images served as a basis, once lightning data detected in 10 minutes (5 minutes before and after the time of each image) were superimposed on the satellite images. This method allowed us to assess the horizontal arrangement of negative and positive CG lightning as function of the brightness temperature of the cloud top during the evolutionary cycle of the systems. At the end of this procedure, image by image, this method also allowed the analysis of the temporal variation of these lightning. A similar procedure was adopted to identify the amount of precipitation caused by each system individually, as well as the spatial and temporal distributions. The results showed a predominance of negative CG lightning during different phases of the systems. Regarding the spatial distribution, negative and positive CG lightning were located mainly in regions where the brightness temperature of the cloud tops were lower than -50°C. A common feature of most systems examined was the generation of greater amount of CG lightning in the first half of the life cycle, during which the highest amounts of precipitation were observed, generally. However, the time of maximum detection CG lightning was lagged regarding the maximum surface precipitation amount, due to the individual characteristics of the analyzed systems.