TITAN : a new infrared radiative transfer model for the study of heterogeneous 3D surface

摘要

An innovative radiative transfer code, TITAN (Thermal Infrared radiance simulaTion with Aggregation modeliNg), in the infrared domain (3-14um) is presented. It takes into account the 3D structure of the landscape and, thus, is able to model the different radiative terms existing in such medium at ground and at-sensor levels. These different terms are solar radiance, atmospheric radiance, emitted radiance and radiance due to the environment. Thus, it allows an accurate spectral analysis of radiative components and of their relative impact to the total signal. Phenomenological analysis of a canyon street is proposed by assessing each term on every points of the modelled surface. Illustrations of the potential of TITAN are given over urban area. Moreover, the impact on the signal when the 3D structure is taken into account by comparing with a "equivalent" flat ground is estimated by calculating the percentage contribution of each term to the total signal at ground level for different wavelengths. Also, multiangular effects of each radiative component are simulated over a 3D street. Thus, these simulations angular variations allow us to quantify the radiative temperature anisotropy and to understand the contribution of each term to this directional behaviour.