Influence of Atmospheric Aerosols on Evapotranspiration over a Semiarid Region in Northeast Brazil

Abstract The knowledge of atmospheric aerosol characteristics at regional and local scales, their temporal changes and interrelations with meteorological variables are of great importance because can modify the global radiative energy balance. This study was carried out to evaluate the influence of aerosols on evapotranspiration over a semiarid region in Northeast Brazil. Aerosol optical depth, global solar radiation, air temperature, air relative humidity, and wind speed were measured in the Research National Center of Semiarid, located at Petrolina, Pernambuco State, Brazil, along two consecutive years. A multivariate model was calibrated and validated for estimating the global solar radiation (Rglobal) based on the aerosol optical depths (AOD) and extraterrestrial solar radiation (R0). Estimates of the reference evapotranspiration (ET0) were obtained by using the FAO standard Penman-Monteith method. Results confirmed that larger aerosol optical depth tends to decrease both Rglobal and ET0. Otherwise, ticker aerosol optical depth tends to absorb less radiation, increasing the ET0. For the semiarid region in Northeast Brazil, most of ET0 deviations were smaller than ±4%. However, higher deviations were also observed, contributing jointly to around 30%, which may result in relevant consequences on the irrigation management, water balance, agroclimatic zoning, among other activities based on the ET0 estimates.