Inclusion of a Simple Vegetation Layer in Terrain Temperature Models for Thermal IR Signature Prediction

A time-dependent energy budget model was designed to enable the prediction of the temperature of terrain scene elements that contain a simple layer of vegetation and to diagnose the effect of vegetation on remotely sensed temperatures. The model was developed for use as a module in conjunction with existing nonvegetated-terrain temperature models. Vegetation was assumed to be a horizontally homogeneous but porous layer partially covering a specified ground surface. Energy budgets for the foliage and the ground were evaluated separately but are interdependent. The sensitivity of the vegetation module (VEGIE), to its input variables when used in tandem with a bare-ground model, TSTM, was examined and found to be most strongly dependent on the degree of foilage cover. The model results were verified against measurements made on two moderate days for a 10-cm high-grass canopy in Germany and were compared to results from a complex vegetation model. Results were highly satisfactory and similar for both models. Both models were also applied to forest canopies where assumptions of the simple model were not valid. As expected, the simple model did not perform well, but the complex model was satisfactory. The VEGIE/TSTM system was then applied to diagnosing the effects of various amounts of foilage cover over low emittance soil, with and without reflection of sky thermal IR energy.