Climatological Water Balance and Calibration of the Nasa Power System for the Southern Region of the Triângulo Mineiro, Brazil

Abstract

The climatological water balance (BHC) is one of several forms of monitoring water storage in the soil, from which water inputs and outputs are determined over a period, using data from several years of temperature, evapotranspiration, and precipitation. In regions without availability of climate data, the database provided by the National Aeronautics and Space Administration/Prediction of Worldwide Energy Resources (NASA/POWER) is a potential source for agrometeorological studies. This study aims to evaluate the water surplus and deficit in the southern region of the Triângulo Mineiro and evaluate the estimates produced by the NASA Power reanalysis. Daily climate data for Frutal and Conceição das Alagoas-MG were used. The BHC were calculated for each city with data obtained by surface meteorological stations and the NASA Power platform for the same period and locations. And finally, the deficit and excess values of water in the soil obtained by BHC by the stations and estimated by NASA Power were compared. The southern region of the Triângulo Mineiro experiences a dry period between the months of April and September, with an average annual total water deficiency (DEF) of 195.1 mm. The water surplus (EXC) averaged 347.8 mm/year, with the months of December and January being marked as a period of water replacement in the soil. For both DEF and EXC, positive correlations were found between the values observed by the station and estimated by NASA Power, with correlation and confidence values greater than 0.90. The accuracy of the models was high with R² greater than 80.0% and absolute errors fewer than 6.0 mm. Based on these findings, precipitation and evapotranspiration remotely detected by NASA Power showed good potential for use in detecting dry and rainy periods, making it possible to support decision-making at relevant scales.