Analysis of a 3D boundary layer model at local scale: Validation on soybean surface radiative measurements

Short and long-wave radiative transfers in the canopy are key components in understanding energy and mass interactions near the surface as well as in the atmosphere upper layers. Consequently, canopy radiative interactions are included in atmospheric boundary layer models. In this paper, a formulation for canopy radiative transfer included in a new 3D boundary layer model is analyzed. The long-wave component is compared to a validated model. We focus our analysis on the downward flux to the soil surface as well as soil surface, vegetation and canopy budgets. In addition, the short-wave component is compared to a consistent four stream model that describes the canopy transmission, reflectance and absorption behavior. Within these comparisons, the long-wave component shows a relatively good agreement between the two models despite the initial hypothesis assumed within the new 3D boundary layer model. Moreover, comparison of the short-wave component to the four stream model reveals the weakness of some hypotheses such as the non-attenuation of short-wave diffuse radiation within the vegetation and the non-conservation of the canopy radiative budget. Therefore, a new and simple parameterization is implemented based on a calibration using the four stream model. After this calibration, comparison to measurements shows a good agreement between observed and simulated net solar and total net radiations of the canopy. This analysis is a promising step in using this new model for investigating the surface energy and mass exchanges within the atmosphere.