Estimation of Daily Reference Evapotranspiration from NASA POWER Reanalysis Products in a Hot Summer Mediterranean Climate

This study aims at assessing the accuracy of estimating daily reference evapotranspiration (ETo) computed with NASA POWER reanalysis products. Daily ETo estimated from local observations weather variables in 14 stations distributed across Alentejo Region, Southern Portugal were compared derived data, using raw and bias-corrected datasets. Three different methods used to compute ETo: (a) FAO Penman-Monteith (PM); (b) Hargreaves-Samani (HS); (c) MaxTET. Results show that, when datasets, a good between observed was most locations (R2 > 0.70). PM shows tendency over-estimating an RMSE as high 1.41 mm d?1, while temperature-based ET estimation method, lower than 0.92 d?1 is obtained. If bias correction adopted, small over or underestimation (–0.40 ? MBE < 0.40 d?1). As for PM, still underestimated 13 (MBE 0 d?1) but never higher 0.77 d?1. When data estimate ETo, HS_Rs proved accurate providing lowest half locations. However, if regional used, leads locations; also, performed, be method Nonetheless, MaxTET method; its simplicity may prove successful not only maximum temperature available also due low required estimation.