During spring snowmelt 1979 and 1980 the runoff from the snowpack was recorded by lysimetry from a 9 m2 area. Wind speed, air temperature, air humidity, radiation, and precipitation data were also recorded. When the melting rate (= snowpack runoff-rainfall) and the net radiation were measured, the turbulent heat exchange between the snowpack and the atmosphere was computed as a residual from the energy balance equation of the snowpack. These computed values were used to find “optimal” empirical constants in aerodynamical equations expressing the turbulent fluxes as functions of the wind speed and the temperature/vapour pressure differences between the measurements 2 m above the ground (0.6-1.5 m above the snow surface) and the values at the surface. These empirical constants agree reasonably well with constants found by other investigators.
Averaged over the two melting seasons, sensible heat flux represents 65%, and net radiation represents 35% of the energy consumed in melting, while 13% was gained from condensation, and 13% was lost by evaporation. When the weather conditions varied during the melting season, the energy balance model yields better results than does the degree-day-model. Residual errors were 7.3 mm (42%) and 13.2 mm (76%), respectively. The maximum melting observed in 24 hours was 110 mm, and the snowmelt rate in overcast days was about 3 times the rate when the cloudiness was light, provided the same wind and temperature conditions and albedo ~ 70%.
- Received September 23, 1981.
- © IWA Publishing 1981