The Simulation Of Snow Processes On Forest And Grass Sites By BAST-SAST Model

A BATS-SAST model was employed to simulate the snow processes in ten snow cases, i.e., Sk_OJP 2001/02, 2002/03, 2003/04 and Sk_HarvestJp 2003/04 of Canada, and Alptal forest site and Alptal open site 2002/2003, 2003/2004, 2004/2005 of Switzerland. At forest site we modified the long wave radiation scheme and precipitation scheme. Considering the different interception between rain and snow and effect of wind and canopy temperature on snow download, we improve the canopy interception model. At open site we modified the snow cover fraction scheme. Results show that model simulates the basic processes of snow cover accurately and describes the features of the snow cover evolutions reasonably. The modified model, which considers the part of the transmitted through the canopy in computing long wave radiation and precipitation at forest site, can make the simulation of upward or downward long wave radiation increased and more closer to the real, but in less snow ablating time it has some decrease. Improving on the net radiation , make the snow depth increased clearly and closer to the observations. However, there is a great different in result change because of the inter-annual variation in snow depth simulation. At open site, there have obvious improvements on simulation of snow depth on the ablation of snow cover. The improved canopy interception model, which influences the variation of snow depth under canopy by changing canopy interception, has a great improvement on simulation of snow depth, especially on the ablation of snow cover.