Snow ablation modeling at the stand scale in a boreal jack pine forest

Abstract

The purpose of this study is to predict spatial distributions of snow properties important to the hydrology and the remote sensing signatures of the boreal ecosystem. This study is part of the Boreal Ecosystems Atmosphere Study (BOREAS) of central Saskatchewan and northern Manitoba. Forested environments provide unique problems for snow cover process modeling due to the complex interactions among snow, energy transfer, and trees. These problems are approached by coupling a modified snow process model with a model of radiative interactions with forest canopies. Additionally, a tree well model describes the influence of individual trees on snow distribution on the ground. The snow process and energy budget model calculates energy exchange at the snow surface, in-pack snow processes, melting and liquid water flow, heat conduction, and vapor diffusion. The surface radiation model provides input on the radiation receipt at the snow surface for model runs in the jack pine forest. Field data consisted of measured meteorological parameters above and within the canopy, spatial variability of snow properties, and variations of incoming solar irradiance beneath the forest canopy. Results show that the area beneath tree canopies accumulated 60% of the snow accumulated in forest openings. Peak solar irradiance on the snow cover was less than one half that measured above the canopy. Model runs are compared between the open and the forested sites and show the open area ablating four days before areas beneath the canopy and eight days before forest openings and compare favorably with measured data. Physically based modeling of snow ablation was successful at the forested site and nearby open area.