Use of satellite soil moisture to diagnose climate model representations of European soil moisture - air temperature coupling strength

The interaction between soil moisture and air temperature is a key factor affecting European summer air temperature variability. Therefore, accurately representing soil moisture controls on local air temperatures may improve projections of future European heat wave frequency. However, modeled estimates of soil moisture - air temperature coupling strengths contain large uncertainties and inter-model differences, and general circulation models (GCMs) are hypothesized to generally underrepresent European land-atmosphere coupling. However, due to a lack of spatially extensive ground-based soil moisture observations, model-based predictions of soil moisture - air temperature coupling strengths have not been adequately verified. Here, we utilize remotely sensed soil moisture retrieval products to evaluate soil moisture - air temperature coupling strength estimates provided by seven Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models. Soil moisture retrievals provided by the NASA Soil Moisture Active/Passive (SMAP) mission are shown to be uniquely suited for this purpose. Based on comparisons to SMAP-based coupling values, we demonstrate that CMIP5 models generally underestimate soil moisture - air temperature coupling strengths - particularly in central Europe. This provides new observational evidence for a low bias in GCM representation of European soil moisture - air temperature coupling strength.