资源环境科技发展态势分析平台

Runoff parameterizations currently adopted by the (i) NoahMP model, (ii) Community Land Model (CLM), and (iii) CLM with variable infiltration capacity hydrology (CLMVIC) are incorporated into the structure of Noah land surface model, and the impact of these parameterizations on the runoff simulations is investigated for a Tibetan river. Four numerical experiments are conducted with the default Noah and three aforementioned runoff parameterizations. Each experiment is forced with the same set of atmospheric forcing, vegetation, and soil parameters. In addition, the Community Earth System Model database provides the maximum surface saturated area parameter for the NoahMP and CLM parameterizations. A singleyear recurrent spinup is adopted for the initialization of each model run to achieve equilibrium states. Comparison with discharge measurements shows that each runoff parameterization produces significant differences in the separation of total runoff into surface and subsurface components and that the soil water storagebased parameterizations (Noah and CLMVIC) outperform the groundwater tablebased parameterizations (NoahMP and CLM) for the seasonally frozen and highaltitude Tibetan river. A parameter sensitivity experiment illustrates that this underperformance of the groundwater tablebased parameterizations cannot be resolved through calibration. Further analyses demonstrate that the simulations of other surface water and energy budget components are insensitive to the selected runoff parameterizations, due to the strong control of the atmosphere on simulated land surface fluxes induced by the diurnal dependence of the roughness length for heat transfer and the large water retention capacity of the highly organic top soils over the plateau.