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The objective of this study is to evaluate spatial and temporal variations in rainfall aggressiveness in southern Brazil. A total of 181 rain gauge stations located in southern Brazil with rainfall time series from 1976 to 2015 were used. Seasonal and annual rainfall aggressiveness values measured according to the Modified Fournier Index (MFI) were analyzed. The trends in the data series were evaluated using the Mann-Kendall test at a level of significance of 5%. Maps on spatial and seasonal variations in rainfall aggressiveness were prepared. The percentage of rain gauge stations with significant decreasing trends, significant increasing trends, and no significant trends in rainfall aggressiveness between years was 3.3%, 7.7%, and 89.0%, respectively. Moreover, 90% of stations had no significant trends between seasons. There were seasonal differences in rainfall aggressiveness between the three southern states in Brazil caused by rainfall factors. Rainfall aggressiveness was comparatively higher in the west of Santa Catarina and southwest of Paraná due to the rains originating from the mesoscale convective systems predominant in autumn, and in the north coast of Santa Catarina and east coast of Paraná due to convective and orographic precipitations predominant in the summer.

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A erosão hídrica superficial é um dos grandes problemas ambientais, que causa degradação das terras agrícolas, contaminação dos recursos hídricos e assoreamento dos reservatórios. Este trabalho teve como objetivo analisar os dados dos pluviogramas das estações de Itajaí e Indaial, localizadas na Bacia do Rio Itajaí, com a finalidade de avaliar a erosividade das chuvas e ajustar as equações para estimar o índice de erosividade a partir das médias pluviométricas da região. A metodologia usada para a determinação da erosividade da chuva foi de acordo com Wischmeier & Smith (1978), baseado na energia cinética da chuva e na intensidade máxima em 30 minutos. Foram ajustadas equações de regressão dos modelos linear e potencial com os valores médios de EI30 e da do coeficiente de chuva (Rc), adotando o modelo que apresentou maior coeficiente de determinação. Com base na série dos dados pluviométricos foram determinados os valores de erosividade média mensal e anual e sua distribuição ao longo do ano para cada estação. Para ambas as estações a equação linear mostrou-se mais indicada, sendo obtidas as equações EI30 = 40,56Rc + 68,74 (R² = 0,7090) e 28,701Rc + 13,54 (R² = 0,8152), respectivamente para Indaial e Itajaí. O valor médio do Índice de Erosividade (R) para Indaial é de 7025,0 MJ mm ha -1 h -1 ano -1 , e para Itajaí de 4756,3 MJ mm ha -1 h -1 ano -1 . Palavras-chave: erosão; sedimentos; chuvas. ABSTRACTThe surface erosion is a major environmental problem, which causes degradation of agricultural land, pollution of water resources, silting of reservoirs. This study aimed to analyze the pluviograms of Itajaí and Indaial stations located in the basin of the Itajaí river, in order to evaluate the erosivity and adjust the equations to estimate erosivity index from the average rainfall in the region. The methodology used to determine the rainfall erosivity was according to Wischmeier & Smith (1978), based on the kinetic energy of the rain and the maximum intensity in 30 minutes. Regression equations were adjusted for linear and potential models with the average values of EI30 and the rainfall coefficient (Rc), adopting the model with the highest coefficient of determination. Based on the series of rainfall data values were determined monthly and yearly average and its distribution throughout the year for each season. For both stations the linear equation was more suitable, and obtained the equationsEI30 =40.56Rc + 68.74 (R² = 0.7090) and Rc =28.701Rc + 13.54 (R² = 0.8152), respectively for Indaial and Itajaí. The average value of Erosivity Index (R) for Indaial is 7025.0 MJ mm ha -1 h -1 year -1, and Itajaí 4756.3 MJ mm ha -1 h -1 yr -1 .