INCLUSION OF GRAVITATIONAL DRAINAGE IN A LAND-SURFACE SCHEME BASED ONTHE FORCE-RESTORE METHOD

This paper presents a simple parameterization of gravitational drainag e for land surface schemes describing soil water transfers according t o the force-restore method of Deardorff. A one-year time series of obs erved soil moisture period from HAPEX-MOBILHY (Hydrological Atmospheri c Pilot Experiment-Mobilisation du Bilan Hydrique) 1986 revealed the i mportance of subsurface drainage during the wintertime period. This ph ysical process is accounted for through a Newtonian restore to field c apacity when soil moisture is above it. Simulation of the annual cycle of soil moisture by the land surface scheme ISBA (interactions soil b iosphere atmosphere) is in this way greatly improved.