The Sensitivity of Land-Atmosphere Coupling to Soil Moisture Over the Tibetan Plateau Based on the Improved Noah-MP Model

Abstract

While land-atmosphere water-heat exchange critically influences climate variability and the water cycle, particularly in cold regions, it is inadequately comprehended due to insufficient observational data. This study aims to improve the performance of the community Noah land surface model with multiparameterization options (Noah-MP) model in water and heat transfer simulations and explore the sensitivity of regional land-atmosphere coupling to soil moisture over the Tibetan Plateau. The model is evaluated against data from eight eddy covariance sites, four soil temperature and moisture networks, and seven reanalysis products. Various sensibility tests are conducted, including the replacement of soil property, surface drag coefficient scheme, canopy stomatal resistance scheme, soil surface resistance scheme, and their different combinations. The results indicate that different schemes can improve certain aspects of model simulations. Specifically, the modified surface drag coefficient scheme reduces the overestimation in sensible heat flux by adjusting the surface heat exchange coefficient, while the improved stomatal and soil resistance schemes enhance latent heat flux and soil moisture simulations. The optimal combination significantly reduces average bias by 61.3% for the Bowen ratio, 9.6% for soil temperature, and 50.0% for soil moisture. Regional simulations demonstrate that sensible heat flux constitutes the primary constituent within the energy partitioning, characterized by a mean Bowen ratio of 1.84. In arid and semiarid zones, the Bowen ratios are 3.10 and 1.75, respectively, underscoring stronger surface energy exchange capacity over drier soil conditions.