To better resolve the changing snowmelt and glacier hydrology of western North America, improved representations of surface heterogeneity, snowpack processes and snow-albedo feedback are needed in the current generation of RCMs. Multiple factors control mountain snowpack accumulation and ablation, including elevation, slope, aspect, wind, and vegetation. Snow melt is also affected by the evolution of the snowpack through the melt season, e.g. the influences of impurities, water content, and recrystallization on snow albedo; the effects of internal and overnight refreezing; the development of surface features that influence snowpack roughness (hence, turbulent exchanges).
It is proposed here to develop a subgrid-scale snow (SSS) parameterization to consider land surface heterogeneities on snowpack conditions within regional climate models (e.g., Liston 2004; Déry et al. 2004). Use of elevation bands, consideration of slope and aspect, and exposure to wind will be factored in the SSS parameterization. This effort will be developed in concert with subproject C3 to ensure transferability to glacier surfaces. The aim of this work is to improve the depiction of snowpack evolution in western North America and impacts on the regional hydrology in the CRCM5. Simulations will focus on the Columbia, Fraser, Mackenzie and Nelson river basins (and some of their major tributaries) for which observed hydrometric and snow data are available (e.g., Déry et al. 2012).
This project will answer the following important questions: Can high-resolution model integrations with subgrid-scale snow parameterization simulate snow in mountainous regions? How snow changes in future impact the regional hydrology? How does the snow-albedo feedback in models compare to those observed?