Snow surface energy exchange

The release of snow in the form of melt water is important to agriculture, hydroelectric power generation, urban water supply, and flood control over a large part of the Northern Hemisphere. One of the factors governing the rate of production of melt water is the energy exchange at the snow surface. The two most important exchange processes are radiation transfer (short‐ and long‐wave) and the turbulent exchange process (sensible and latent heat transfer). The present review considers these two processes exclusively. The radiation exchange is frequently the dominant transfer process during snowmelt on the prairies, in the northern forests, and in mountainous terrain. Methods for modeling radiation on an areal basis during clear days in open areas are well advanced and agreement between calculations and measurements is good although measured data are scarce in the literature. The presence of a forest cover or cloudy skies complicates the modeling process, but relatively simple procedures have been developed in the past few years which are sufficiently accurate for many water management purposes. Sensible and latent heat transfer has been measured at a variety of sites throughout the world. When results are compared it is obvious that such factors as prevailing air mass conditions, altitude, time of year, and terrain features influence the relative importance of turbulent exchange and radiation transfer. As yet there are insufficient data to distinguish trends among these factors with any clarity although the air mass is clearly important and should be considered in future studies of the energy exchange process.