Evaluation of snowpack and glacier dynamics using a physically parameterized hydrological land surface scheme and in-situ meteorological forcing in the Canadian Rockies

Abstract:

High mountains snow and ice processes are strongly influenced by precipitation, blowing snow redistribution, sublimation, and the exchange of radiative and turbulent fluxes. This work evaluates the coupled hydrology land-surface model (MESH), using the Canadian Land Surface Scheme (CLASS) at different alpine and glacierized research sites in the Canadian Rockies. Here a physically based modeling approach based on the understanding of the hydrological system was used. Model parameters were set using information acquired from several decades of process hydrology research in the high mountain sites of the Canadian Rockies. For the different sites (e.g. alpine ridges, glacier, alpine forests and clear cuts, and montane sites), the model was run in single column mode and forced by 30-min meteorological observations collected as part of the Canadian Rockies Hydrological Observatory. The forcing data of shortwave and longwave irradiance were adjusted to slopes; meanwhile, air temperature, humidity, pressure and precipitation were adjusted for elevation to the single column model site. The simulations were evaluated against snow and ice observations. Overall, MESH showed good performance in capturing snow accumulation, snowmelt onset, and ablation rates from snow and ice. On wind-blown, high alpine ridges, the model could simulate SWE well when its blowing snow algorithms were used. Simulations of snow accumulation under forest canopies were acceptable, suggesting that snow interception and sub-canopy snow energetics were well simulated. The MESH glacier algorithms were able to simulate snow and ice ablation on a glacier. The falsification of the driving meteorology by not accounting for terrain impacts on radiative forcing and for elevational impacts on precipitation and temperature caused maximum SWE differences and shifts in the timing of snow disappearance at the high mountain sites. The underestimation of the high mountain snowpack had significant impact at the glacier site resulting in an overestimation of meltwater from the exposed glacier ice.