Impact of the new Noah Land Surface Model on the NCEP Climate Forecast System (CFS)

The NCEP Noah land surface model (LSM) will be coupled to the NCEP Climate Forecast System (CFS) and assessed as an alternative to the Oregon State University (OSU) LSM used in NCEP's currently operational CFS. As an important benchmark for this investigation, the Noah LSM was recently implemented in NCEP's operational Global Forecast System (GFS) for medium-range weather prediction. The major upgrades provided by the Noah LSM deal largely with cold season processes (frozen soil and snowpack physics), but also include improvements related to number of soil layers (increased from 2 to 4), fraction of green vegetation cover, bare soil evaporation, and soil heat flux under vegetation and wet soils. The recent refinement of some parameters (particularly in the canopy resistance formulation) during the aforementioned GFS implementation will be included as well.

The new coupled system (CFS/Noah) will be tested for the winter of 2002-2003 and summer of 2004, which is the field phase of the N. American Monsoon Experiment (NAME). A new snow albedo algorithm, including an application of a new MODIS-based global maximum snow albedo field, will be tested in the winter cases. The initial Noah land states will be taken from the Global Land Data Assimilation (GLDAS) executing the Noah LSM (see separate abstract by Jesse Meng). The results will be assessed with some of the surface-flux station observations of the 41 globally distributed reference sites of the GEWEX CEOP program to investigate how much impact the Noah LSM can bring to the seasonal predictions of the NCEP CFS.