Tuesday, 15 January 2002: 4:00 PM
The Effects of Implementing TOPMODEL Concepts in the NOAH Model
This paper will demonstrate the impact of topographic control of runoff production and lateral soil water redistribution on the water and energy balance as simulated by the NCEP/OSU/AFWA/NWS OH NOAH land surface model (Mahrt and Ek, 1984; Mahrt and Pan, 1984; Pan and Mahrt, 1987; Chen et al., 1996; Schaake et al, 1996; Chen et al., 1997; Mitchell, 1999). In its original form, the NOAH model solves the Richards equation for 1-D vertical soil water transport in each land surface model grid, which corresponds to the atmospheric model horizontal grid. There is no provision in the original model for lateral soil water redistribution or for explicit subgrid soil moisture heterogeneity. The following aspects of the NOAH model have been modified or replaced with new parameterizations based on TOPMODEL concepts: drainage parameter “SLOPE”; infiltration/runoff generation parameter “REFKDT”; and a non-linear soil moisture stress function for stomatal resistance. One of the key results of the work is the importance of properly re-scaling TOPMODEL input parameters such as the topographic index. Results demonstrating the impact of these concepts on the land surface water and energy balance will be presented based on a series of off-line, retrospective simulations.