Validation of the Global Land Data Assimilation System with the measurements of soil temperature profiles over grassland regions

Abstract:

Soil temperature is a key parameter in the soil-vegetation-atmosphere system. It plays an important role in the land surface water and energy cycles, and has significant influence on yield of agricultural crops and vegetation growth. We evaluated the accuracies of the soil temperature profiles from the Global Land Data Assimilation System (GLDAS) at nine observational networks in the world to find a reliable global soil temperature profile dataset for future hydrological and ecological studies. Comparing with in-situ observations at different soil depths, the soil temperature profile data generated by the Noah model driven by the GLDAS forcing data (GLDAS/Noah10) and its latest version (GLDAS/Noah10_v2) were found skillful in terms of daily, monthly, and mean seasonal variations, showing great potential for applying these data in global hydrological and ecological studies. Further analysis showed that the overestimation of the GLDAS/CLM10 was mainly caused by its overestimation of ground heat flux, whereas the underestimation of the GLDAS/Noah10 was due to underestimation of downward longwave radiation from the forcing data. Thus, more accurate forcing data for the Noah model and improved thermal parameterization scheme for the CLM should be a future focus, as they can improve the simulation of soil temperatures.