Investigating the relationship between soil moisture and evapotranspiration at different surfaces. Do we improve fluxes just improving the land use in models?

A correct spatial representation of the surface energy balance is still a challenge. In a first step, and assuming a correct knowledge of the incoming short-wave radiation, it is the land cover that mostly controls the albedo and the long-wave radiation emitted to the atmosphere, influencing significantly the net radiation available at the surface and the surface temperature. In a second step, the partitioning of this energy into evapotranspiration and sensible heat flux is, in part, controlled by the availability of soil moisture but also by the type, characteristics and physiological state of the vegetation covering the surface, since plants provide a pathway for soil moisture to the atmosphere through transpiration.

Hence, to correctly model the surface energy balance, we face three main challenges: an appropriate representation of the land use, soil moisture and a correct modelling of how plants regulate their stomatal behaviour under different soil-moisture limited conditions.

In this work, by using in situ data we explore the relations between soil moisture and evapotranspiration from several vegetation types at different soil-moisture limited regions: a wetter area in the south of France and a drier one in the south of Spain. For this, we try to distinguish different periods and vegetation states. Since significant differences are observed for the various plant types, we investigate whether using a more realistic and higher-resolution land-use database in the Weather Research and Forecasting (WRF) model improves the simulation of soil moisture and surface fluxes.