Snow Albedo in Forested Regions

Abstract:

Snow albedo is considered to be a primary control on radiation balance in snow-covered regions. Over 70% of seasonally snow-covered land is forested yet there are remarkably few studies of how snow albedo is affected by forests. Moreover, those measurements have focused on mid-latitude forests. We present recent findings showing that snow albedo in forested regions is significantly decreased by forest litter even when albedo values are refreshed by recent snowfall. Across a forest density gradient, the accumulation of forest litter is greatest in the dense forest and decreases at the forest edge and is lowest in open areas. However, the low snow albedo due to forest litter accumulation has little impact on net shortwave radiation in the dense forest because of low solar irradiance in the forest (Figure 1). As forest density decreases, the importance of snow albedo increases in controlling net shortwave radiation and the overall snowpack energy budget. These results guide our planning for a notional albedo study in the Alaskan Arctic where seasonal changes in insolation, forest density, and wildfire disturbance combine to affect the radiation budget, and snowpacks are particularly vulnerable due to accelerated climate warming. Based on our prior study and its findings, and the characteristics of taiga forest in the Arctic, we outline a plan to quantify snow albedo and its impacts on the region. Due to reductions in forest density as a result of fire, we expect the snow albedo impact under burned forest will be amplified across the burned area, particularly near gaps and edges. We map out land cover and seasonal changes in insolation -- showing how geospatial analysis can be used to provide transferability of results.