SHORT-TERM AND LONG-TERM VARIABILITY OF SNOW ALBEDO

The progress of snow albedo for the 1991 winter from Helligdagshaugen research site, Norway, is presented. The temporal reduction of albedo decreases as the snow undergoes a process of metamorphosis, as long as the snow depth is large enough to prevent absorption of solar radiation by the underlying terrain. Later, as the snow depth becomes less than about 10 cm and the area of bare patches grows, there is an increase in the temporal rate of reduction in albedo. An accumulated daily maximum temperature index is shown to be a good predictor of both the long-term development of the snow albedo and the daily mean albedo. The actual albedo deviates from the predicted long-term albedo due to variable meteorological conditions of which solar radiation is the most important one. Solar radiation and snow albedo are negatively correlated. Linear regression is performed for a winter period with no melting and for two distinct melting periods. Snow albedo was first determined as a function of temperature index alone. An improved accuracy of 2-6 per cent in estimated snow albedo was obtained when solar radiation was included. Very similar regression coefficients were found for two different periods.