THE EFFECTS OF CANOPY COVER AND SHADING ON SURFACE HOAR SIZES IN SMALL FORESTED MEADOW OPENINGS

ABSTRACT: Understanding variations in slope scale snowpack properties influences stability assess-ments at the slope and regional scale. Previous studies have shown that surface hoar, a prominent weak layer type, can vary in initial crystal size and height across small, seemingly homogenous meadows and sparsely forested areas on northerly aspects. The differences in size have generally been attributed to the radiation balance, which is difficult to estimate in the field. This study aims to further investigate the effect of canopy cover and shading on the growth of surface hoar in small forested meadow openings just after initial growth and prior to burial. Two small (approx. 30m x 50m) study plots located in southwest Montana were selected. The study plots, one northern and one southern aspect, are mostly planar 10 ° meadows surrounded by heavy tree cover. We collected 200 samples with 2119 individual crystal observations, and estimated shading and hemispheric sky visibility to explain the difference in sizes of surface hoar in each meadow. Findings indicate that the strength of these determinants varies depending on aspect and how the surface hoar size is determined