Impact of Oceanic Oscillations in Annual Trends of Precipitation Extremes in the Paraíba do Sul River Basin Assessed Based on the PSL Daily Gridded Precipitation Dataset

Abstract The waters of the Paraíba do Sul River supply around 15 million people, most of whom live in metropolitan regions of the state of Rio de Janeiro. Climate change alters its precipitation regime and can cause an increase in the occurrence of extreme hydrological events. The variability of precipitation results from the combined effects of the surface conditions of the oceans and the variations in the dynamics of atmospheric systems. This work aims to detect possible changes in the climatic extremes of precipitation in the Paraíba do Sul hydrographic basin and to investigate evidences of correlation of these indices with the oceanic oscillations associated with the El Niño-Southern Oscillation, Pacific Decadal Oscillation, North Atlantic Oscillation and Atlantic Multidecadal Oscillation. Results indicate that the eastern and northeastern sectors of the basin present trends of increase in the total annual precipitation, in the number of very humid days and in the occurrence of extreme events, in a space of time up to five days. The west and southwest sectors, on the other hand, show decreasing trends in total annual precipitation, in the number of very humid days, but with an increase trend in the maximum amount of rainfall on five consecutive days. The central sector has characteristics of a transition zone. The correlation analyzes show that the majority of the oceanic oscillation indices have a very weak correlation with the extreme precipitation indices, while the wavelet transform does not indicate significant power at the low frequencies.