A Study of Rainfall Interception Using a 1And Surface Parameterization for Mesoscale Meteorological Models

Abstract

Rainfall interception by vegetation canopies is studied using a parameterization of land surface Processes for mesoscale meteorological models. The interception scheme allows for a single vegetation canopy, and manages interception through a prognostic variable representing the amount of liquid water retained by the foliage. A set of 24 h simulation fully interactive with the boundary layer, is carried out with a one-dimensional model in order to examine the sensitivity of the interception scheme to vegetation properties. The evaporation from the interception reservoir is strongly enhanced by high values of the roughness length. The leaf area index, acting on the maximum storm capacity, modifies the drying time of the foliage. As a first stage of validation, the interception scheme is compared with other models developed for hydrological purposes. It appears that the scheme is not very different from the single-layer Rutter model, which has been well tested and validated. Only minor differences are noticed between the results of the two models. The scheme is also compared with a multilayer model that provides a more physical description of the rainfall interception. The main departure concerns the drying time of the canopy, which is almost independent of the rainfall rate in the single-layer model. Finally, a validation of the interception scheme is made using micrometeorological data from the HAPEX-MOBILHY experiment. Six simulations lasting 24 h indicate that the parameterization reproduces quite well the daily evolution of the components of the surface energy balance for various surface conditions and various rainfall distributions.