Cloud-to-ground lightning in southeastern Brazil in 1993. I - Geographical distribution

About 1.1 million cloud-to-ground lightning flashes were recorded by a lightning positioning and tracking system in southeastern Brazil in 1993. The one-year continuous lightning data set is the first obtained in Brazil. It was analyzed for geographical distribution of total flash density, percentage of positive flashes, negative and positive flash densities, and negative and positive flash peak currents. The dependence of the flash density and peak current on latitude, altitude, and soil resistivity was investigated. Negative flash peak current was found to be inversely correlated with latitude, but no other significant correlation was found for flash density and peak current with these parameters. Positive flashes were found to be contaminated by intracloud flashes. The maximum total, negative, and positive flash densities were 15.5, 9.1, and 7.7 flashes/sq km per year, respectively. The average percentage of positive flashes was 36.5 percent. The geometric means of negative and positive peak current were 30.9 and 17.8 kA. The high density, high percentage, and low average peak current of positive flashes found in this study are probably a result of such a contamination. (Author)