Snow Interception Relationships with Meteorology and Canopy Structure in
a Subalpine Forest
Abstract
Snow accumulation models differ in how snow interception and ablation
processes are represented and thus their application to diverse climates
and forest types is uncertain. Existing parameterizations of initial
snow interception before unloading include inherently coupled canopy
snow accumulation and ablation processes. This leads to difficulty in
diagnosing processes and adding possible errors to simulations when
incorporated as canopy interception routines in models that already
account for canopy snow ablation. This study evaluates the theory
underpinning parameterizations of initial snow interception using
high-temporal resolution and fine-scale measurements of throughfall for
events with minimal snow ablation and redistribution in both the canopy
and on the ground. The relationship between these throughfall
measurements, event meteorology, and a novel lidar-based canopy
structure measurement are assessed in two subalpine forest plots in the
Canadian Rockies. Contrary to existing theories, no association of
canopy snow load or air temperature with interception efficiency was
observed. Instead, canopy structure emerged as the primary factor
governing snow accumulation. A wind-driven snowfall event demonstrated
that non-vertical hydrometeor trajectories can significantly increase
snow-leaf contact area, thereby enhancing initial interception before
ablation. Prediction of interception efficiency for this event improved
dramatically when adjusted for hydrometeor trajectory angle based on a
wind speed at one-third of the canopy height. Snow-leaf contact area
showed a high sensitivity to wind speed, increasing by up to 95% with a
1 m s -1 wind speed. The study proposes a new
parameterization that calculates throughfall, independent of processes
that ablate snow from the canopy, as a function of snow-leaf contact
area adjusted for hydrometeor trajectory angle. This new
parameterization successfully estimated subcanopy snow accumulation for
a snowfall event at two forest plots measured using lidar and snow
surveys. By separating canopy snow ablation from snow interception
processes, this new model offers potentially improved prediction of
subcanopy snow accumulation when combined with canopy snow ablation
parameterizations.