Abstract
Abstract. In this paper, we investigate the ability of the Noah Land Surface Model (LSM) to simulate temperature states in the soil profile and surface fluxes measured during a 7-day dry period at a micrometeorological station on the Tibetan Plateau. Adjustments in soil and vegetation parameterizations required to ameliorate the Noah simulation on these two aspects are presented, which include: (1) differentiating the soil thermal properties of top- and subsoils, (2) investigation of the different numerical soil discretizations and (3) calibration of the parameters utilized to describe the transpiration dynamics of the Plateau vegetation. Through the adjustments in the parameterization of the soil thermal properties (STP) simulation of the soil heat transfer is improved, which results in a reduction of Root Mean Squared Differences (RMSD's) by 14%, 18% and 49% between measured and simulated skin, 5-cm and 25-cm soil temperatures, respectively. Further, decreasing the minimum stomatal resistance (Rc,min) and the optimum temperature for transpiration (Topt) of the vegetation parameterization reduces RMSD's between measured and simulated energy balance components by 30%, 20% and 5% for the sensible, latent and soil heat flux, respectively.
Highlights
An accurate characterization of the heat and moisture exchange between the land surface and atmosphere is important for Atmospheric General Circulation Models (AGCM) to forecast weather at various time scales (i.e. McCumber and Pielke, 1981; Garratt, 1993; Koster et al, 2004)
Noah simulations obtained by using default parameterizations are compared to soil temperature and surface energy balance measurements
The Root Mean Squared Differences (RMSD) and the bias are calculated between the measurements and simulations, and presented in Tables 5 and 6 for the surface energy balance components as well as the www.hydrol-earth-syst-sci.net/13/759/2009/
Summary
An accurate characterization of the heat and moisture exchange between the land surface and atmosphere is important for Atmospheric General Circulation Models (AGCM) to forecast weather at various time scales (i.e. McCumber and Pielke, 1981; Garratt, 1993; Koster et al, 2004). An accurate characterization of the heat and moisture exchange between the land surface and atmosphere is important for Atmospheric General Circulation Models (AGCM) to forecast weather at various time scales Within operational AGCM these land-atmosphere interactions are described by a Land Surface Model (LSM). Because AGCM are computationally demanding, numerical efficiency of the LSM is required. A simplified implementation of the physical processes and the applied parameterizations are inevitable. The impact of a physically based formulation of roughness lengths for momentum and heat transport on the calculation of the surface fluxes has been stressed A limited number of soil and vegetation parameterizations are accommodated in modeling systems operational at a global scale A limited number of soil and vegetation parameterizations are accommodated in modeling systems operational at a global scale (e.g. Ek et al, 2003)
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