The Tibetan Plateau is a key region of land-atmosphere interactions, as itprovides an elevated heat source to the middle-troposphere. The Plateausurfaces are typically characterized by alpine meadows and grasslands in thecentral and eastern part while by alpine deserts in the western part. Thisstudy evaluates performance of three state-of-the-art land surface models(LSMs) for the Plateau typical land surfaces. The LSMs of interest are SiB2(the Simple Biosphere), CoLM (Common Land Model), and Noah. They are run attypical alpine meadow sites in the central Plateau and typical alpine desertsites in the western Plateau.The identified key processes and modeling issues are as follows. First, soilstratification is a typical phenomenon beneath the alpine meadows, withdense roots and soil organic matters within the topsoil, and it controls theprofile of soil moisture in the central and eastern Plateau; all models,when using default parameters, significantly under-estimate the soilmoisture within the topsoil. Second, a soil surface resistance controls thesurface evaporation from the alpine deserts but it has not been reasonablymodeled in LSMs; an advanced scheme for soil water flow is implemented in aLSM, based on which the soil resistance is determined from soil watercontent and meteorological conditions. Third, an excess resistance controlssensible heat fluxes from dry bare-soil or sparsely vegetated surfaces, andall LSMs significantly under-predict the ground-air temperature gradient,which would result in higher net radiation, lower soil heat fluxes and thushigher sensible heat fluxes in the models. A parameterization scheme forthis resistance has been shown to be effective to remove thesebiases.
展开▼
