An intercomparison of three snow schemes of varying complexity coupled to the same land surface model: Local-scale evaluation at an Alpine site

The Interactions between Soil, Biosphere, and Atmosphere land surface schem e is currently used coupled both to atmospheric models and to a distributed hydrological model. There are two snow-scheme options available for hydrol ogical modeling: the baseline force-restore approach, which uses a composit e snow-soil-vegetation energy budget and a single snow layer; and a multila yer detailed internal-process snow model. Only the force-restore method is routinely used in atmospheric modeling applications. Recent studies have sh own that hydrological simulations for mountainous catchments within the Rho ne basin, France, are significantly improved using the detailed snow scheme . The main drawback is that the scheme is computationally expensive, and it is not currently feasible for routine application in atmospheric models. F or these reasons, a third new intermediate-complexity scheme has been devel oped that includes certain key physical processes from the complex model fo r improved snowpack realism and hydrological depiction while attemping to k eep computational requirements similar to those of the simple default schem e. In the current study, the new scheme is described, evaluated, and compar ed with the results from the two other schemes at a local scale at an alpin e site located within the Rhone basin for two contrasting (weather) years. All schemes are able to model the basic features of the snow cover with sim ilar errors averaged over the 2-yr period; however, there are important dif ferences on shorter timescales. When compared with the more complex scheme, it was found that differing surface energy budget parameterizations (turbu lent transfer, albedo) were the cause for the largest differences in total snowpack snow water equivalent (SWE) simulated by the models. When compared with the simple scheme, the ability for the intermediate model to simulate snow ripening resulted in the largest differences in simulated SWE and sno w temperature during melt and runoff.