Recent Developments in RUC Land Surface Model (RUC LSM) Implemented in Operational Rapid Refresh (RAP) at NCEP

Further refinements to the RUC soil/snow/vegetation/sea-ice model (RUC LSM) implemented in the NCEP operational WRF-ARW-based Rapid Refresh (RAP) were developed and introduced. Most recent changes were directed towards more accurate representation of land surface sub-grid scale variabilities via implementing a mosaic approach to the calculation of such surface parameters as Leaf Area Index (LAI), emissivity, roughness length and soil properties, as well. Also, seasonal variations of LAI and roughness length were introduced, and logarithmic formulation to the computation of effective roughness length in the grid cell was applied. In addition, the vertical configuration of RUC LSM was changed from 6 to 9 levels with even higher resolution near the soil/atmosphere interface. Latest improvements to RUC LSM snow model include modifications to snow albedo and roughness length, and more accurate representation of snow cover on the ground via enhanced use of NESDIS IMS snow product not only to trim excessive cycled snow, but also to build snow in the areas where it is missed or melted too soon. These modifications were implemented in the developmental Rapid Refresh (RAP) at NOAA/ESRL and provided more realistic surface conditions through cycling of soil temperature, soil moisture, canopy water, snow depths and snow temperatures for improved wind, dew point and temperature predictions near the surface. Following extensive testing at ESRL, they are planned to be implemented in the second version of the operational Rapid Refresh (RAP) at NCEP in 2014.