Development of a Land Surface Model. Part I: Application in a Mesoscale Meteorological Model

Abstract

Parameterization of land surface processes and consideration of surface inhomogeneities are very important to mesoscale meteorological modeling applications, especially those that provide information for air quality modeling. To provide crucial, reliable information on the diurnal evolution of the planetary boundary layer (PBL) and its dynamic characteristics, it is necessary in a mesoscale model to include a land surface parameterization that simulates the essential physics processes and is computationally efficient. A land surface model is developed and implemented in the Fifth-Generation Pennsylvania State University?National Center for Atmospheric Research Mesoscale Model (MM5) to enable MM5 to respond to changing soil moisture and vegetation conditions. This land surface model includes explicit soil moisture, which is based on the Interactions between Soil, Biosphere, and Atmosphere model and three pathways for evaporation, including soil evaporation, canopy evaporation, and vegetative evapotranspiration. The stomatal conductance, leaf-to-canopy scaling, and surface moisture parameterizations are newly developed based on a variety of sources in the current literature. Also, a processing procedure for gridding soil and vegetation parameters and simulating seasonal growth has been developed. MM5 with the land surface model is tested and evaluated against observations and the ?standard? MM5, which uses a simple surface moisture availability scheme to estimate the soil wetness and then the latent heat flux, for two cases from the First International Satellite Land Surface Climatology Project Field Experiment. The evaluation analysis focuses primarily on surface fluxes of heat and moisture, near-surface temperature, soil temperature, PBL height, and vertical temperature profiles. A subsequent article will describe extensions of this model to simulate chemical dry deposition.