DESEMPENHO DE METODOLOGIAS PARA ESTIMATIVA DO SALDO DE RADIA??O A PARTIR DE IMAGENS MODIS

摘要

The present study intends to evaluate the performance of different methodologies used in estimating the instantaneous net radiation (Rn), which is the main energy source to various natural processes occurring on the surface of our planet. The study area belongs to the Mogi Guacu River Basin. The surface data used for the Rn calibration and validation are from two micrometeorological towers located in areas of cerrado and sugarcane. MODIS sensor images and the SEBAL, METRIC and Bisht et al. methodologies were compared. Rn in the cerrado area always showed higher values than that of sugarcane, indicating that, in those wild areas, there is therefore a greater amount of energy to transform into latent and sensible heat fluxes. The employed methodologies were quite satisfactory, with a best performance of the METRIC methodology. The fact that the methodology Bisht et al. does not require surface data appears to be quite useful, since in the absence of surface measurements it has been a frequent and no-cost option for the user to make estimates of net radiation.