The 2019/2020 and 2020/2021 droughts events in Southern and Southeastern Brazil

Drought is a highly intricate hazard that can be challenging to define and detect. Its impact can be felt across numerous sectors and timeframes. The configuration of La Nina conditions is linked to drought conditions in Southern and Southeast Brazil, especially during late spring and summer months. Since late 2019, two successive La Nina events have resulted in various degrees of drought in the southern region of Brazil, causing significant effects on multiple sectors such as agriculture, water resources, and energy production. The 3-month Standardized Precipitation Index (SPI) timescale was utilized to define and characterize the drought conditions. In this study, a drought event starts when the analyzed indicator falls below a certain negative standard deviation value (e.g. SPI-3 < -1) for at least two consecutive months, and ends when the indicator rises above 0, following the methodology described in Spinoni et al. (2019). The aim of this work is to examine and compare the differences between the two drought episodes that occurred during the spring and summer of 2019/2020 and 2020/2021, respectively, and to understand the variations in their severity. Four different sources of monthly precipitation data were used: the ERA-5 global reanalysis dataset, CHIRPS and PERSIANN satellite datasets, and automated weather stations from INMET. A comparison is performed among these four datasets to identify if there is an impact in drought characteristics, such as area, duration and intensities. This study also explores the impact of large-scale circulation and sea surface temperature indices, namely El Nino 3.4, Indian Ocean Dipole (IOD), South Atlantic Subtropical Dipole mode (SASD), and South Atlantic Ocean Dipole mode (SAOD), on the two recent drought episodes.