Impact of surface heterogeneity on temperature, mass and energy exchanges

In an attempt to provide more accurate estimates of sensible and latent heat fluxes and surface temperature, a 3- dimensional model is being developed. The originality of this model is to rely on a realistic description of the studied landscape: architecture, temperature, optical properties. It combines 3 components: (1) a radiative component managed by the 3-D radiative transfer DART model which simulates the 3-D distribution of absorbed and emitted radiation by the Earth surface and also directional reflectance and temperature images in the optical domain, (2) a vegetation functioning component managed by the leaf photosynthesis model of Collatz and (3) a micrometeorological component managed by a simple parameterization of turbulence. This integrated model simulates the major vegetation and environmental processes at the root of mass and energy fluxes. Consequently it allows one to quantify how within cover, temperature and radiation distributions affect both vegetation functioning and remote sensing measurements. It is in its first stage but preliminary results are promising. Its applications are varied: to better understand interactions between vegetation architecture and functioning, to become a reference model for simpler models and also to better understand and use remotely sensed data.