Snow-Albedo Feedback and the Spring Transition in a Regional Climate System Model: Influence of Land Surface Model

Amanda H. Lynch, David L. McGinnis and David A. Bailey

Abstract

Using the Arctic Regional Climate System Model (ARCSyM), we investigate the spring seasonal transition and mechanisms controlling snow melt over a domain covering the northern half of Alaska. Annual simulations for 1992 comparing the BATS and LSM land surface schemes show the BATS experiment enters the spring transition with respect to the large scale atmospheric regime approximately one month earlier than observed climate and the LSM experiment transitions a month later than observed, even though the air temperature in the LSM experiment is generally warmer than in the BATS experiment. A more detailed examination reveals that each simulation commences and completes the snow melt period at about the same time, but that the LSM snowmelt is more rapid than in the BATS experiment. Controlling the snow melt is the initial snow pack depth and the surface energy budget, both of which involve a complex series of feedbacks between shortwave and longwave radiation, cloud, surface turbulent fluxes, and vegetation. The snow melt over tundra regions dominates the more rapid snow melt seen in the LSM simulation. It is determined that the most crucial differences between the BATS and LSM schemes are the partitioning of net ground heat flux between patches of snow and bare ground, and the formulation of snow albedo.