Soil Moisture Conditions Determine Land-Atmosphere Coupling and Drought Risk in the Northeastern United States

Strengthened land-atmosphere coupling in the northeastern United States (NEUS), accompanied by a positive soil moisture-rainfall feedback, may lead to more drought. Coupling between the land and atmosphere emerges when low soil moisture values limit surface latent heat flux, or evapotranspiration, so that a majority of absorbed solar radiation is emitted from the surface as sensible heat. In this study, the Weather Research and Forecasting model was run with four prescribed soil moisture levels across 7 years to elucidate the strength of land-atmosphere coupling under potential, future soil moisture states in the NEUS. Under drier conditions, land-atmosphere coupling strengthens, and a positive soil moisture-precipitation feedback develops in all years despite differences in the amount of moisture advected into the study domain. As snowpack decreases and evaporative demand increases, soil conditions may become drier in future summers over the NEUS, resulting in the more frequent development of drought.