Technical note Analysis of a simplified relation for estimating daily evapotranspiration from satellite thermal IR data

Abstract Estimation of evapotranspiration from thermal infrared (IR)as been widely studied in recent years and in particular by methods using the simplified relation ETR − R n = A − B(T s−T a) proposed by Jackson et al. (1977) and thermal IR data from the NOAA satellite obtained near midday (local time). The representativeness of instantaneous temperature for computing daily fluxes is discussed and a one-layer model is presented for a developed crop. A new theoretical expression of the simplified relation which can be applied to developed crops is presented and the sensitivity of the parameters in this relation is examined. Additional informationNotes on contributorsA. VIDAL CEMAGREF, Remote Sensing Division, BP 5095, 34033 Montpellier Cedex, France.