Heat exchange and melt of late season snow patches in heavy forest

An analysis is presented of observations in mid-July over a continuously melting snow patch in a dense forest during five days of clear, calm weather. Each heat component is evaluated from measurements (and supplementary estimates), of long-wave and short-wave radiation, of free air temperature and humidity at a meteorological station, and on rather crude measurements of condensation and of air temperature gradients close to the snow. The snowmelt equivalent of heat supply is compared with measured ablation. Approximately 50% of melt at the snow surface was due to long-wave radiation, 20% to convective heat, 15% to latent heat of condensation and 15% to short-wave. Thus, 85% of the melt was accounted for by air temperature and humidity, ordinarily available at a meteorological station, and 15% by short-wave radiation which can be estimated from records of insolation elsewhere. The results of the study are formulated in a melt equation involving only linear functions of air temperature, humidity and short-wave radiation.Discussion by Walter U. Garstka.