Changes in the spatial-temporal patterns of droughts in the Brazilian Northeast

In Northeast Brazil (NEB), severe droughts have high socioeconomic impacts. In this study, the spatial-temporal characteristics of drought were evaluated based on a new drought index at 4-km spatial resolution, derived from regional empirical relationships between a remote sensing-based index and rain-gauge-based standardized precipitation index (SPI), a well-known drought meteorological index. This index was used to compare the spatial pattern of severe drought events (1982-1983, 1992-1993, 1997-1998, and 2012-2013) of the last 30years. Strong ElNino related droughts were found to be generally spatially limited, affecting around 30% of NEB and concentrated in the northern part of the region, while 2012 drought, which was not ElNino related, was widespread, reaching 46% of NEB. These results stressed the importance of analyzing droughts at the subregion scale using data with higher spatial resolution. Statistically significant trends (p<0.05) toward drier conditions detected in the SPI time-series were linked to the tropical Atlantic Ocean warming trend, which result in an increased drought risk and social vulnerability in the region.