Identificação de secas no Estado de Alagoas via Standardized Precipitation Index (SPI)

Abstract

Drought is a natural disaster caused by the lack of rainfall for a certain period ranging from a month to years. Despite some studies on the theme of drought in the state, there are still gaps to be filled, especially an analysis of the impacts on agriculture caused by drought in the climatic mesoregions of Alagoas (Arid Zone, Hinterland e Coast). Therefore, this study evaluated drought episodes in the State of Alagoas in the period 1960-2016, based on the Standardized Precipitation Index (SPI). Monthly rainfall data from 54 stations belonging to the hydrometeorological network of the National Water Agency (ANA) were used however, such data had flaws in the time series and were filled in via the method of imputation of data in the R environment. via annual SPI (SPI-12) was related to the phases of the El Niño-Southern Oscillation (ENSO) mode of variability via the Oceanic Niño Index (ONI), followed by the effects of drought and in two agricultural crops (sugarcane and cassava) in the state. The SPI-12 maps were used using the Inverse Distance Weighted (IDW) interpolation method from Quantum Gis (QGis) version 3.4.6. The results obtained showed that the SPI-12 is a satisfactory index for the identification of annual drought in the state. The hot phase of ENSO (El Niño) contributed to the intensification of the drought, especially in the 2015/2016 cycle in the very dry SPI category. It is worth noting that this cycle is classified as a very strong El Niño, according to ONI. Although the decrease in agricultural production of sugarcane and cassava occurred in years of moderately dry to extremely dry events, the correlation is not satisfactory, as there were years with negative SPI events, which did not influence the decrease in agricultural production in the year State. It is worth highlighting the continuity of studies based on the SPI and its relationship with changes in land use and occupation, climate variability mode - Pacific Decadal Oscillation (PDO) and, mainly, comparing the performance of the SPI with other drought indices for the State, for example, Standardized Precipitation Evapotranspiration Index (SPEI) and Palmer Drought Severity Index (PDSI), which use other parameters and climatic variables in addition to rainfall.