LST-based Analytical Solution of Conductance and Evapotranspiration: Validation over All Semi-Arid FLUXNET Sites

We present a novel method to analytically resolve terrestrial evapotranspiration (ET) and conductances (both boundary layer, gB, and surface, gS) using MODIS LST, radiation and meteorological variables This consists of a set of equations where we have expressed these unknown internal state variables in terms of the known core variables combining diffusion equations, Penman – Monteith and Bouchet's Complementary hypothesis. The estimated ET is compared with a suite of established global ET models (MOD16, PT-JPL and SEBS) and validated with observations over all the semi-arid FLUXNET eddy covariance sites as well as agro-ecosystems of SMEX02. The performance of this LST-based single source ET model (LSSEM) is remarkably good particularly during the dry down period in Mediterranean savanna where ET is strongly governed by the subsurface soil moisture and where the majority of the ET models show poor results. This method does not require any parameterization, site specific calibration or spin-up and free from parameterization uncertainties. Initial promise of LSSEM over semi-arid landscape points to its immense potential to apply from the future NASA mission having thermal sensors like HyspIRI for producing field scale ET for agroecosystems monitoring.