Hydrometeorological Drivers of Western US Summertime Temperature Variability in Global Climate Models

Abstract

Interannual variations in summertime temperature have a large impact on drought, fire, and extreme heat across the Western United States. We investigate the influence of antecedent hydrological conditions on the leading pattern of Western US summertime temperature variability in global climate model (GCM) simulations and find that Western US summertime heating is associated with antecedent Southwest US springtime soil moisture deficit and wintertime precipitation deficits across all six of the CMIP6 models in our analysis. Furthermore, the relationship between Western US summertime temperature and Southwest US wintertime precipitation is disrupted in experiments where soil moisture variations were removed. Our results suggest that springtime soil moisture anomalies in the Southwest US drive variations in summertime temperature throughout the Western US and that land-atmosphere coupling in this region can impart predictability at seasonal time scales.