Monthly distribution of cloud-to-ground lightning flashes as observed by lightning location systems

This paper presents a comparison among the mean monthly distributions of the number of cloud-to-ground (CG) flashes, the percentage of positive CG flashes and the peak current of negative and positive CG flashes obtained in Brazil for the period from 1999 to 2004, with the same distributions observed by similar networks for long time periods in other countries. From a correlation analysis, it was found that the mean monthly distributions of the number of CG flashes are very similar, even though the period of larger lightning activity along the year in Brazil, a tropical country, is longer than in the other temperate countries. The mean monthly distributions of the percentage and the peak current of positive CG flashes are also very similar, while the mean monthly distribution of the peak current of negative CG flashes in Brazil differs from the other countries. This difference is related to a significant decrease in the mean negative peak current in Brazil in the months of August and September. Apparently, the decrease is related to the injection in the atmosphere of large amounts of smoke from fires in these months, since the results also show a significant correlation between the monthly distribution of the number of fires and the negative peak current.