A study of the lightning characteristics in Brazil based on an analysis of the performance of the lightning location system / Estudo de relâmpagos no Brasil com base na análise de desempenho do sistema de localizacao de tempestades

AUTOR(ES)
DATA DE PUBLICAÇÃO

2000

RESUMO

The harmful lightning effects on the mankind have motivated several investigations on lightning characteristics in the world and, particularly, in Brazil. Many studies on the geographic, seasonal, topographic and demographic features of lightning have been done using lightning location systems (LLS). The LLS, which is located in the southeastern region of Brazil, is a complex measurement system composed by a network of sensors that detects the electromagnetic radiation of the discharges over a wide continental area and sends these informations to a central processing unit the location of the lightning strike point and the main physical parameters are then precisely calculated. These data play a significant role on the development of the lightning research in specific areas and periods. On the other hand, the LLS presents limitations that should be studied in order to assure more realistic results. The objective of this work is to develop a preliminary analysis of the LLS Performance and the influence of its configuration on the lightning data. A study of the lightning seasonal and geographic characteristics during summer and winter seasons of 1999 and 2000 are then performed based on this analysis. The main conclusions reveal that the percentage of positive flashes is significantly greater in winter (about 23) than in summer (about 5.7). The peak currents of negative lightning are less intense than the peak currents of positive flashes. Negative flashes tend to be more intense in summer with a mean peak current of 36.9 kA. The correspondent winter value is 29.9 kA. Positive lightning present an inverse behavior with a mean value of 46.9 kA in summer and 50.5 kA in winter. It was observed that single lightning (both positive and negative)were less intense than the first return stroke of multiple lightning. the negative lightning have a greater number of return strokes with a mean value of 1.74 while in positive lightning the mean multiplicity is 1.05. The multiplicity does not present a significant seasonal variation for both polarities. Also, a preliminary study of lightning occurrence over highly populated areas was developed during the summer seasons of 2000 and 2001. The results reveal that lightning tend to concentrate over large urban areas, as the metropolitan regions of São Paulo, Campinas and Vale do Paraíba. It is supposed that population growth and urbanization are responsible for this specific behavior due to the atmospheric pollution and deforestation which cause local meteorological changes.

ASSUNTO(S)

tempestades relâmpagos medidas eletromagnéticas electromagnetic measurement radiacao eletromagnética aquisicao de dados thunderstorms lightning geofÍsica espacial sensors data acquisition sensores electromagnetic radiation

ACESSO AO ARTIGO

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