Snow-Atmosphere Coupling Strength. Part II: Albedo Effect Versus Hydrological Effect

In this study of snow-atmosphere coupling strength, the previous snow-atmosphere coupled modeling experiment is extended to investigate the separate impacts on the atmosphere of the radiatively driven snow albedo effect and the snow hydrological effect that operates through soil moisture, evapotranspiration, and precipitation feedbacks. The albedo effect is governed by snow cover fraction, while the hydrological effect is controlled by anomalies in snow water equivalent. Realistic snow cover from satellite estimates is prescribed and compared with model-generated values to isolate the snow albedo effect. Similarly, imparting realistic snow water equivalent from the Global Land Data Assimilation System in the model allows for estimation of the snow hydrological effect. The snow albedo effect is found to be active before, and especially during, the snowmelt period, and regions of strong albedo-driven coupling move northward during spring, with the retreating edge of the snowpack in the Northern Hemisphere. The snow hydrological effect appears first during snowmelt and can persist for months afterward. The contributing factors to the snow albedo effect are analyzed in a theoretical framework.