Variations in Extreme Precipitation and Associated Impacts on Natural Disasters in Southeastern Brazil: a 1979-2023 Analysis

The knowledge of the distribution of precipitation and its extremes, both spatially and temporally, is important for planning various human activities such as agriculture, civil defence, energy production, and urban planning. Heavy precipitation events associated with climate change had become more frequent and pronounced in many regions of Brazil, culminating in significant environmental, social, and economic damage across the country. In this context, the main objective of this work was to identify the trends and behavior of intense precipitation events (above the 95th percentile) across all states in southeastern Brazil. Daily precipitation data, at grid points, were obtained from the Climate Prediction Center (CPC) for the period from 1979 to 2023. The results showed that the number of days above the 95th percentile exhibited a significant increase during the summer and spring months, particularly in the south and west of São Paulo and the north of Minas Gerais. In general, negative trends above the 95th percentile were observed over the east of São Paulo and the metropolitan region of Rio de Janeiro, indicating that extreme rainfall was not constant over time. These results seemed contradictory when compared with the number of days above the 95th percentile, which varied between 150 and 300 days during the summer, autumn, and spring months, and around 400 days in the winter months. Therefore, it was concluded that intense precipitation was concentrated in a few days, separated by longer dry spells. By relating the patterns of rainfall trends above the 95th percentile and the number of days with records of landslides and floods, it was found that these disasters were located in areas of extreme rainfall or positive trends, especially during the summer and spring months. In general, persistent events were observed with more than two (three) consecutive days with rainfall above P95 over the states of MG and RJ (MG and SP). Finally, the periods with the highest number of days above the 95th percentile can could be related to the predominance of the South Atlantic Convergence Zone and more frontal system activity.