Different approaches in estimating heat flux using dual angle observations of radiative surface temperature

In this study, the issue of estimating sensible heat flux from dual angle observations of radiative surface temperature has been addressed using both model-generated and field data. The adopted approach consisted of coupling a two-source Soil-Vegetation-Atmosphere Transfer (SVAT) to a physically based radiative transfer model in the thermal infrared bands (RTM-TIR 0 ) which allowed for simulating convective fluxes and components and directional temperature under different surface and atmospheric conditions. The simulated directional temperatures were used to invert components surface temperature using three radiative transfer models (RTM-TIR 1,2,3 ) with different degrees of complexity. The inverted component temperatures were then used to simulate sensible heat flux. These heat flux values were compared to those obtained using the coupled model. The results showed that as far as the heat flux is concerned, there is no need for a complex RTM-TIR. Indeed, the fluxes simulated with the three simplified RTM-TIRs compared well with those using the physically based one. These results were confirmed using field data collected during the SALSA experiment. Based on this finding and using the three simplified RTM-TIRs we developed a generic parameterization where sensible heat flux was analytically expressed in terms of the (nadir) radiative-air temperature gradient and a corrective term involving the nadir-oblique temperature differences. The performance of the approach has been successfully evaluated using both model generated and field based data.