The use of fractual geometry in modelling intercepted snow accumulation and sublimation

In the boreal forest, interception of snow can store 60% of cumulative snowfall in mid-winter and sublimation of this snow can return over 30% of annual snowfall to the atmosphere as water vapour. A sublimation algorithm for a single ice sphere and an ‘exposure coefficient’ which accounts for the difference in surface area to mass ratios between intercepted snow and the ice sphere permit calculation of the sublimation rate in coniferous canopies. Fractal geometry provides a tool to calculate this exposure coefficient from digitised photographs of snowcovered canopies. Intercepted snow is fractal and the irregularity of its shape depends on locaton in the canopy and age of the snow. The fractal shape of intercepted snow permits a relationship between snowcovered area in canopy photographs and interception load. The analysis shows the feasibility of a physically-based model of intercepted snow accumulation and sublimation that uses standard meteorological measurements and digitised photographs of the canopy.