Intercomparison of micrometeorological variables, surface energy fluxes, and evapotranspiration in different landscapes of the Brazilian semi-arid region

Abstract

The comparison of energy exchanges between different landscapes is very valuable for understanding the consequences of deforestation and land use change on the climate. In this study, we analyzed micrometeorological variables, energy fluxes, and actual evapotranspiration over four landscapes of the Brazilian semi-arid region (preserved Caatinga – CAA, regenerating Caatinga – REGE, cactus landscape – CAM and deforested landscape – DEFA). Micrometeorological measurements (air temperature and relative humidity, vapor pressure deficit), net radiation (RN), latent heat (LE), sensible (H) and soil heat (G) fluxes, actual evapotranspiration (ET), and soil water storage variation (ΔS) were obtained in landscapes from October 2018 to September 2020. LE and H were calculated based on the Bowen ratio method. Significant differences were noted between micrometeorological variables (temperature and relative humidity, and vapor pressure deficit) and energy flux among the four landscapes. The four surfaces exhibited, on average, lower LE values when compared to H. At CAA landscape, 35% of the RN was used for LE, 64% for H, and 1% for G, versus 33% for LE, 65% for H, and 2% for G at REGE; 33% RN for LE, 65% for H and 2% for G at CAM, and 40% for LE, 59% for H and 1% for G at DEFA. The evapotranspiration for regenerating Caatinga (1.62 mm day−1), cactus (1.59 mm day−1), and deforested area (1.90 mm day−1) were higher than the preserved Caatinga (1.40 mm day−1). However, seasonal variations of the ET were more associated with fluctuations in RN, rainfall, and ΔS than with the type of land use. It is concluded that the removal of Caatinga by landscapes such as regenerating Caatinga, cactus plantations, and deforested area significantly modifies micrometeorological variables, energy fluxes, and the evapotranspiration, but their seasonality depends on the regime availability of water and energy.