The impacts of Soil Properties on the water and energy cycles modeling of Noah-mp in China

Land surface models are useful tools in investigating water and energy cycle. Soil hydraulic properties (SHP) play a major role in the hydrological and ecological processes crossing scales. However, many land models determine SHP only based on land use and soil types, neglecting the heterogeneity of SHP. We hypnotize that using distributed SHP, both horizontally and vertically, could further improve the physics and performance of land surface models.

This study evaluates the performance of Noah-MP land model using distributed SHP. We first perform variance-based Sobol sensitivity analysis to detect the global sensitivity of nine of the Noah-MP parameters to output water and energy variables. Based on the sensitivity analysis, we carry out regional simulation to evaluate the effects of spatial SHP on Noah-MP simulated water and energy cycle, we mainly focus on pore size distribution index, saturated water content, saturate hydraulic conductivity, which can be obtained from various soil datasets. The simulation is configured for the mainland of China and run at 3-hourly 0.1°×0.1°resolution between 1981 and 2018. Results show that, when compared to the lookup table soil parameterization schemes, using distributed SHP not only improves the accuracy of simulated runoff and evapotranspiration, but also enhances Noah-MP in characterizing the reliability of soil moisture spatial pattern in six major river basins of China. In addition, the vertical heterogeneity to the SHP further increases NSE of runoff and lowers RMSE of soil moisture.

This study suggests that Noah-MP performance can be improved by using value of distributed and vertical heterogeneity of soil properties as input of soil hydraulic parameters.