Evaluation of Soil Moisture in CMIP6 Multimodel Simulations Over Conterminous China

Abstract

AbstractThe Sixth Phase of the Coupled Model Intercomparison Project (CMIP6) provides the long‐term soil moisture (SM) products and this study conducts a comprehensive assessment of SM products of multiple CMIP6 model simulations over conterminous China. Both near‐surface (0–10 cm) SM simulations from 40 models and root‐zone (0–100 cm) SM from 25 models are compared with a set of in situ and a satellite‐based data set in the growing season for 1992–2013. The long‐term trend and interannual variability of near‐surface SM for 1961–2014 are further evaluated with an offline land surface modeling data set. Simulations from most models broadly capture the spatial characteristics of observation, and the multimodel mean (MME) well reproduces seasonal variations over the majority of regions, regardless of the large spread across models. SM from CMIP6 models from the same institution likely manifests similar performances, which indicates that the land‐surface scheme plays a dominant role in the CMIP6 SM reproduction. The majority of CMIP6 models well simulate the overall drying trend in China as a whole and the signs of a SM trend are highly consistent across different models, but the areas with significant wetting/drying trends vary with models. The spatial patterns of SM interannual variability are model‐dependent. MME is overall superior to the simulation of individual model and may have potential applications in future research. The heterogeneity of SM performances across CMIP6 models reveals the complexity and uncertainty in modeling land surface variables, suggesting the need for improving representations of land surface processes in the coupled models.