How does reanalysis handle snow cover?
[11/14/97] The snow coverage was estimated from satellite imagery (once per week) and snow coverage was converted into a snow depth by assuming it is a simple function of the surface temperature. (Yes, it is unrealistic but we have no snow depth observations.) For the purposes of data assimilation, the snow depth is not critical. Radiative properties depend on the coverage rather than depth. In addition, if the snow coverage happened to melt away (because the snow wasn’t deep enough), the snow coverage gets reinitialized with “observations” every six hours. It is suggested that snow coverage be used rather than the snow depth; i.e., convert the snow depth (WEASD) into 1’s or 0’s. The skin temperature over a snow surface is determined by a balance of the fluxes. Net solar + net long wave + sensible + latent + conduction through the snow layer + snow melt = 0. The snow melt term is set to the minimum amount required to keep the the skin temperature at or below freezing. Within the snow l
