Spatio-temporal Characterization of Droughts in Northeast based on the Analysis of the SPI Index

Abstract

Here we characterize the spatio-temporal patterns of droughts in the Brazilian Nordeste through a Principal Component Analysis (PCA) of the Standardized Precipitation Index (SPI), obtained from rainfall data for the 1980-2013 period. In the first PC, that responds to 42% of the data variability, we observe a homogeneous drought throughout the region. The second PC is responsible for 11% of the data variance and presents a north-south dipole pattern. From the historical series of the two PCs, we objectively identified the most severe and extreme droughts, which coincided with the driest years reported in the literature, such as 1982 and 1993. However, to the best of our knowledge this is the first work to show the exact location and area of Nordeste hit by each extreme drought identified. We also show the less intense droughts that do not appear in the literature, such as those that took place in 1981, 1996 and 1998 and hit between 20% and 36% of the region. Moreover, a cross-correlation analysis of the PCS and the NINO3.4 and tropical Atlantic dipole indexes revealed that the influence of such indices on the droughts in the regions act at different temporal scales with distinguished spatial impacts.

Keywords:
droughts; SPI; Northeast Brazil; spatial-temporal variability