The Priestley-Taylor equation applied to pixel scale: An alternative for detailed studies of basins [La ecuación de Priestley-Taylor aplicada a nivel de píxel: Una alternativa para estudios detallados de cuencas]

摘要

The estimate of potential daily evapotranspiration (LE_d) is of great interest on a local and regional scale. Currently, scale regional estimates are conducted from the combination of field data with satellite images (SI). This paper presents a methodology of simple application to estimate the LE_d on a regional scale by means of the equation of Priestley and Taylor (1972) (PT) and a model to obtain daily net radiation (Rn_d) pixel by pixel. Rn_d model was developed from local data recorded by an energy balance station (EBS) in the sub-humid pampean region of Argentina, resulting Rn_d=A.Rs↓_d.(1- albedo) + B, where A and B are two experimental parameters and Rs↓_d is daily short wave incoming radiation. Rnd model was combined with the PT equation and was applied to obtain LE_d on a pixel scale (30 m by 30 m) using the calculated albedo from a Landsat SI (TM sensor), the alpha PT parameter was set in 1.26 and ground heat flux in zero on a daily scale. LE_d maps were developed for 6 consecutive days, where LEd temporal variation is mainly regulated by the Rs↓_d and spatial variation of the albedo. Although the model proposed has not been validated with local measurement or other models, a estimation of the uncertainty in the methodology used to determine LEd was 22%, which suggests being a good alternative for its application in the pampean region of Argentina or other similar regions of the world.