Heat Exchange across a Snow Surface at 5365 Meters, Mt. Logan, Yukon

Abstract

The surface heat balance is seldom investigated at high alpine altitudes, and more rarely in combined high latitude-high altitude environments. This paper reports summertime energy-balance results from the 5365 m snow plateau on Mt. Logan, Yukon (60°36′N, 140°30′W). The research station was located at a pressure level close to the 500-mb surface and experienced below-freezing temperatures throughout the summer season. For the period 30 June to 21 July 1970, the heat balance was small (the largest overall flux was a net radiation −4.9 MJ · m⁻² · day⁻¹), with largest individual fluxes represented by incoming and outgoing shortwave radiation (32.2 and 28.8 MJ · m⁻² · day⁻¹, respectively). Net radiation losses at this high altitude were nearly balanced by heat gained from sublimation and riming. Sensible heat transfer to the snow represented only a 12% contribution to the energy balance — an artifact of the topographic sheltering effect on wind and the cold air ponding that frequently took place. Conduction of heat into the Logan snowpack was negligible over the measurement period. Mt. Logan's energy-balance regime resembles, in part, many high-latitude snow environments — except for the high proportional gain to the snow by sublimation and riming.