Abstract ID: 3.11393 | Accepted as Talk | Talk/Oral | TBA | TBA

Forested mountains characterize the snowy headwaters of many major river basins, where snow accumulation can be reduced by up to 50% through canopy snow interception and subsequent ablation. Accurate modelling of the seasonal subcanopy snowpack requires a comprehensive understanding of these processes. However, existing theories on snow interception and canopy snow ablation have uncertain application in differing environments and spatial scales. Recent observations in the Canadian Rockies have revealed novel insights into snow interception and canopy snow ablation processes. Subcanopy throughfall and canopy structure measurements from aerial LiDAR, combined with high-frequency lysimeter measurements of canopy snow load and unloading challenged the theory behind existing parameterizations and informed the development of improved process representations. This presentation describes a new snow interception parameterisation that calculates throughfall based on forest structure and models canopy snow ablation through a combined approach: an energy balance method for snowmelt and empirically-derived functions for snow unloading. The new parameterisation better captures observed stand-scale processes, including enhanced interception efficiency during wind-driven snowfall events and subsequent increases in canopy snow unloading due to wind, snowmelt, and sublimation. The improved canopy snowmelt energy balance also accounts for sub-zero temperature melting driven by longwave emission from warm canopy elements and limitations on nighttime sublimation imposed by radiative cooling. To assess the effectiveness of these new parameterisations, both the new and traditional routines were implemented in the Cold Regions Hydrological Modelling platform and evaluated against observations of subcanopy snow water equivalent and canopy snow load at sites not used in model development, including the continental climate Marmot Creek, Alberta; subarctic climate Wolf Creek, Yukon Territory; and coastal climate Russell Creek, British Columbia (all in Canada). Preliminary results demonstrate substantially improved subcanopy snow predictability, with R² values increasing from 0.4 using existing methods to 0.7 with the revised routine. This enhanced process-based understanding of snow interception and canopy snow ablation shows promise for broader application in water resource assessment of forested, snow-dominated basins.