Spatio-temporal variability of wet and drought events in the Parana River basin-Brazil and its association with the El Nino-Southern oscillation phenomenon

This study aimed to analyse the spatio-temporal variability of wet and drought events in the Parana River Basin and their association with the El Nino-Southern 20 Oscillation (ENSO) phenomenon. A dataset of daily precipitation from 953 pluviometric stations from 1982 to 2016 was used. Anomalies of sea surface temperature (SST) from the four Nino regions of the Equatorial Pacific were also used. Homogeneous rainfall regions were defined using cluster analysis and principal component analysis (PCA). To describe the drought or wet conditions the standardized precipitation index (SPI) for 1-, 3-, and 12-months time scales were used. The relationship between the ENSO and the wet and drought conditions were also analysed. The results suggest that two regions are enough to represent the whole Parana River Basin during different rainfall patterns. In the 1-month SPI, the precipitation extremes of the region that is mainly composed of the state of Parana and southern region of Mato Grosso do Sul (Region 2), showed a statistically significant correlation at the level of 1% with ENSO events. In the 12-month SPI, the most intense drought and wet events and with greater spatial coverage, in general, were observed in years with ENSO occurrences. In general, it is observed that although the ENSO phenomenon is not the main factor that causes the drought and wet events in the region, El Nino contributes to the rainfall excess and La Nina to the rainfall deficit in the Parana River Basin.