Evaporation of intercepted snow: measurement and modelling

Snow storage on a coniferous forest canopy was measured using gamma-ray attenuation and tree weighing systems, along with measurements of throughfall, using two plastic sheet net rainfall gauges. Meteorological parameters were measured with an automatic weather station. Estimates of evaporation of intercepted snow show an average rate of 0.24 mm h(-1) and a maximum cumulative total of 3.9 mm in 7 h. Comparison with evaporation determined by a combination method with two different estimates of aerodynamic resistance (the "standard" rain aerodynamic resistance nu(aL) and a snow aerodynamic resistance nu(aS)-an order of magnitude larger than nu(aL)) showed that nu(aL) overestimated the evaporation by a factor of 2.6, whereas nu(aS) gave fair agreement with the measured evaporation. A multilayer model may be needed to take into account the variations of latent heat source area. Using the long-term measurements of the weight of snow on a single tree the total interception evaporation was estimated to be of the order 200 mm year(-1). (C) 1998 Elsevier Science B.V. All rights reserved.