Yihua Wu1,2, Mike Ek2 Brad Ferrier1,2
1IMSG at NOAA/NCEP/EMC 2NOAA/NCEP/EMC 5830 University Research Court College Park, Maryland 20740, USA
Snow cover significantly affects the earth surface albedo which can lower the short wave radiation absorbed by the surface and increase long wave radiation emitted by the surface. Snow cover can also cause insulating effects of snow for vegetation and wildlife. Accurately forecasting snow fall and surface snow accumulation is important because of the dramatic impacts on all modes of transportation and the activities of millions of people. In the previous version of NAM, surface snow was accumulated based on the binary assumption of snow or no-snow, and surface snow density was based on the lowest model level air temperature. Recently, precipitation type from microphysics was provided as input to the land surface model (Noah) to expand the range of possible snow densities. Higher ice densities allowed greater snow density, which in turn decreased the snow depth. Incorporating this information into snow density calculation in the land surface model was based on the hypothesis that forecast of snowfall would be improved in regions with mixed-phase precipitation. More numerical experiments will be conducted to validate this approach. Primary results will be shown in this presentation.