Development of a simple parametric model to simulate the directional effects in the thermal infrared domain

Correction of the directional effects affecting satellite measurements in thermal infrared (TIR) require simple methods robust enough to be easily integrated into data processing chains. The ability of a simple parametric model based on an analytic formulation of the hot spot to estimate directional TIR anisotropy is tested. For this purpose, the necessary data are provided using the deterministic model SCOPE (Soil Canopy Observations, Photochemistry and Energy fluxes, Van der Tol et al. 2009) as a data generator. SCOPE is first validated against experimental energy fluxes and directional temperatures measured over winter wheat and pine stands. Then, the sensitivity of anisotropy to several parameters (leaf area index, water stress, wind speed and hot spot parameter) is illustrated. Finally the parameters of the simplified model are derived by inverting SCOPE simulated data. The comparison of directional anisotropy for zenith viewing angles lower than 35° reveals absolute error lower than 0.3K.