Climatological data from three stations in western Canada are used to develop a model for estimating daily net radiation from station latitude, station altitude and cloud cover. Expressions describing: a) the seasonal variation in atmospheric transmissivity; b) the interaction between direct-beam and diffuse short-wave radiation and c) the effect of cloud cover on these components are presented.
The seasonal decrease in albedo of a shallow snowcover is approximated by three line segments. Albedo decreases at an average rate of 0.0061/day during premelt; at an average rate of about 0.071/day during melt and takes on a reasonably constant value of 0.17 when the ground is snowfree.
The exchange of long-wave radiation dominates the radiation balance of a complete snowcover. During these periods it is recommended that the net flux be calculated from observations of ambient air temperature and vapor pressure in standard expressions.
- Received February 27, 1990.
- Accepted May 28, 1990.
- © IWA Publishing 1990