Studies on surface hoar : formation and physical properties

Abstract

Field studies on surface hoar were conducted during the winter months of 1982-83 and 1983-84, at the Big Sky Ski Area, Big Sky, Montana. Mechanical shear strength tests, conducted on established surface hoar layers, indicated that although a layer would become visually undetectable, shear strength remained too low to measure for extended periods of time. The initiation of surface hoar growth was dependent on a variety of near-surface and atmospheric conditions. Nocturnal clear-sky radiative heat loss from the snow surface did not necessarily predispose condensation onto the surface, although near-surface air temperature gradients would be in excess of +200°C/m. A steady-state approximation for conservation of mass and momentum, in conjunction with the temperature data, predicts that surface crystal growth cannot be a diffusion limited process.