Snow-atmosphere coupling strength in a global atmospheric model

[1] Large scale snow-atmosphere coupling strength (the degree to which the atmosphere responds to anomalies in snow cover) is quantitatively investigated using the Community Land Model (CLM 3.5) and its advanced snow scheme coupled to the Community Atmospheric Model (CAM). An index based on model ensemble statistics has been used to quantify the coupling strength. Multi-seasonal experiments reveal the spatial and temporal distribution of coupling strength during the snow depletion phase (March through June) over the Northern Hemisphere. The snow coupling strength was found to evolve in three distinct stages: before snowmelt, during snowmelt and after snowmelt. The coupling strength is strongest during snowmelt. The coupling strength after snowmelt, mainly due to hydrological effect (soil moisture impact), is stronger than coupling strength due to albedo effect (radiative impact) before snowmelt. A conceptual model is proposed to explain the mechanisms behind the spatial distribution of coupling strength.