Diagnosis of Precipitation and EVI in Two Drought Events on Northeast Brazil

Abstract

The vegetation response is the indicator used to assess drought dynamics in Northeast Brazil (NEB), which has had recurring droughts in the last twenty years. In this work, the general objective was to diagnose the precipitation and Enhanced Vegetation Index (EVI) in two drought events in NEB. Accumulated monthly precipitation data and monthly EVI data during the years 2011-2012 (La Niña) and 2015-2016 (El Niño) were used to evaluate these drought events. In La Niña of 2011-2012, the anomalous pattern in the Tropical Atlantic Ocean was due to irregularities and low precipitation rates in NEB. This effect is mainly observed in the semiarid region, which had precipitation values below 25 mm.month^-1. The EVI showed a decrease in lost biomass between March and September in this region with values lower than 0.3 due to drought. During the El Niño of 2015-2016, there was a subtle increase in precipitation compared to La Niña of 2011-2012, mainly in January. In January, frontal systems detached from the South Atlantic Convergence Zone and from a tropical cyclone, contributed to significant precipitation in the region, especially in the semiarid region, which recorded values higher than 350 mm. This precipitation contributed to increased vegetative content during this period, with EVI values between 0.2 and 0.5, minimizing the drought effects. It was concluded in two events showed that the strong variability on the precipitation regime resulted in the expansion and aggravation of droughts, mainly in the semiarid region.