Spatiotemporal variability of Meteorological drought in MATOPIBA microregions

Abstract

Drought is a recurrent natural event, and its evaluation is important in places susceptible to this phenomenon. This is the case of the extensively explored region known as MATOPIBA, acronym for the four states that compose it (Maranhão, Tocantins, Piauí and Bahia). The objective of this work was to identify and understand the spatiotemporal variability of meteorological drought events that have occurred in the microregions of the MATOPIBA through time series analysis techniques. Monthly historical data series of precipitation and air temperature for the period of 1961-2018 based on CRU-TS-4.03 reanalysis were used. The characterization of the drought was based on the Standardized Precipitation and Evapotranspiration Index (SPEI), specifically the SPEI with a twelve-month incidence (SPEI-12), which characterizes an interface of meteorological drought. Microregions with homogeneous SPEI-12 characteristics were obtained through cluster analysis, as well as non-parametric Mann-Kendall test and Sen’s slope estimator, and Pettitt’s homogeneity tests to investigate the temporal patterns for the region. The analysis of the variability of droughts in the region indicated a progressive increase in the intensity and magnitude of this event throughout the region, especially in more recent periods. Further, Group 5, encompassing a large part of the state of Tocantins (with the exception of three micoregions) and a microregion in the extreme south of Maranhão, was the driest group. In turn, Group 1, which covers the southwest of Maranhão and north of Tocantins, stood out as the most humid in the analyzed period. The trend analyses showed that all micoregions analyzed showed significant decreasing trends, resulting in an increase in drought events in the region during the years evaluated.