Inclusion of Gravitational Drainage in a Land Surface Scheme Based on the Force-Restore Method

J-F. Mahfouf ECMWF, Shinfield Park, Reading, Berkshire, United Kingdom

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J. Noilhan Météo-France/CNRM, Toulouse, France

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Abstract

This paper presents a simple parameterization of gravitational drainage for land surface schemes describing soil water transfers according to the force-restore method of Deardorff. A one-year time series of observed soil moisture period from HAPEX-MOBILHY (Hydrological Atmospheric Pilot Experiment-Mobilisation du Bilan Hydrique) 1986 revealed the importance of subsurface drainage during the wintertime period. This physical process is accounted for through a Newtonian restore to field capacity when soil moisture is above it. Simulation of the annual cycle of soil moisture by the land surface scheme ISBA (interactions soil biosphere atmosphere) is in this way greatly improved.

Abstract

This paper presents a simple parameterization of gravitational drainage for land surface schemes describing soil water transfers according to the force-restore method of Deardorff. A one-year time series of observed soil moisture period from HAPEX-MOBILHY (Hydrological Atmospheric Pilot Experiment-Mobilisation du Bilan Hydrique) 1986 revealed the importance of subsurface drainage during the wintertime period. This physical process is accounted for through a Newtonian restore to field capacity when soil moisture is above it. Simulation of the annual cycle of soil moisture by the land surface scheme ISBA (interactions soil biosphere atmosphere) is in this way greatly improved.

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