NCEP Coupled Climate Forecast System (CFS)     Dynamical Model

NOAA National Centers for Environmental Prediction, Environmental Modeling Center
Camp Springs, Maryland, U.S.

The CFS was developed at the Environmental Modeling Center at NCEP. It is a fully coupled model representing the interaction between the Earth's oceans, land and atmosphere. It became operational at NCEP in August 2004.

The atmospheric component of the CFS is a lower resolution version of the Global Forecast System (GFS) that was the operational global weather prediction model at NCEP during 2003. The ocean component is the GFDL Modular Ocean Model version 3 (MOM3). Improvements in the CFS compared to the previous dynamical forecast system at NCEP includes atmosphere-ocean coupling that spans most of the globe, and the fact that there is no flux correction. More detail on the atmosopheric and ocean components of the CFS follows.

The atmospheric component is the NCEP atmospheric GFS model, as of February 2003 (Moorthi et al. 2001). Except for having a coarser horizontal resolution, it is the same as that used for operational weather forecasting with no tuning for climate applications. It adopts a spectral triangular truncation of 62 waves (T62) in the horizontal (equivalent to nearly a 200 Km Gaussian grid) and a finite differencing in the vertical with 64 sigma layers. The model top is at 0.2 hPa. This version of the GFS has been modified from the version of the NCEP model used for the NCEP/NCAR Reanalysis (Kalnay et al. 1996 ; Kistler et al. 2001), with upgrades in the parameterization of solar radiation transfer (Hou, 1996 and Hou et al. 2002), boundary layer vertical diffusion (Hong and Pan 1996), cumulus convection (Hong and Pan 1998), gravity wave drag (Kim and Arakawa 1995). In addition, the cloud condensate is a prognostic quantity with a simple cloud microphysics parameterization (Zhao and Carr 1997, Sundqvist et al. 1989, Moorthi et al. 2001). The fractional cloud cover used for radiation is diagnostically determined by the predicted cloud condensate.
br /> The oceanic component is the GFDL Modular Ocean Model V.3 (MOM3) (Pacanowski and Griffies 1998), which is a finite difference version of the ocean primitive equations under the assumptions of Boussinesq and hydrostatic approximations. It uses spherical coordinates in the horizontal with a staggered Arakawa B grid and the z-coordinate in the vertical. The ocean surface boundary is computed as an explicit free surface. The domain is quasi-global extending from 74°S to 64°N. The zonal resolution is 1° The meridional resolution is 1/3° between 10°S and 10°N, gradually increasing through the tropics until becoming fixed at 1° poleward of 30°S and 30°N. There are 40 layers in the vertical with 27 layers in the upper 400 m, and the bottom depth is around 4.5 Km. The vertical resolution is 10 m from the surface to the 240-m depth, gradually increasing to about 511 m in the bottom layer. Vertical mixing follows the non-local K-profile parameterization of Large et al. (1994). The horizontal mixing of tracers uses the isoneutral method pioneered by Gent and McWilliams (1990) (see also Griffies et al. 1998). The horizontal mixing of momentum uses the nonlinear scheme of Smagorinsky (1963).

The atmospheric and oceanic components are coupled with no flux adjustment or correction. The two components exchange daily averaged quantities, such as heat and momentum fluxes, once a day.

View the CFS web page , containing much information and data.

View the current 3-month average Nino3.4 SST forecasts.

Contact: cfs@noaa.gov

References:
Gent, P. R. and J. C. McWilliams, 1990: Isopycnal mixing in ocean circulation models. J. Phys. Oceanogr., 20, 150-155.
Hong, S.-Y. and H-L. Pan, 1996: Nonlocal boundary layer vertical diffusion in a medium-range forecast model. Mon. Wea. Rev., 124, 2322-2339.
Hong, S-Y and H-L. Pan, 1998: Convective Trigger Function for a Mass-Flux Cumulus Parameterization Scheme. Mon. Wea. Rev., 126, 2599-2620.
Hou, Y-T, K. A. Campana and S-K Yang, 1996: Shortwave radiation calculations in the NCEP's global model. International Radiation Symposium, IRS-96, August 19-24, Fairbanks, AL.
Hou, Y., S. Moorthi,. K. Campana, 2002: Parameterization of solar radiation transfer in the NCEP models. NCEP Office Note, 441. http://www.emc.ncep.noaa.gov/officenotes/FullTOC.html#2000
Kalnay, E. and Coauthors, 1996: The NCEP/NCAR 40-year Reanalysis Project. Bull. Amer. Meteor. Soc., 77, 1057-1072.
Kim, Y-J and A. Arakawa, 1995: Improvement of orographic gravity wave parameterization using a mesoscale gravity wave model. J. Atmos. Sci., 52, 11, 1875-1902.
Kistler, R., E. and Coauthors, 2001: The NCEP-NCAR 50-Year Reanalysis: Monthly Means CD-ROM and Documentation. Bull. Amer. Meteor. Soc., 82, No. 2, 247-268.
Large, W. G., J. C. McWilliams, and S. C. Doney, 1994: Oceanic vertical mixing: A review and a model with nonlocal boundary layer parameterization. Rev. Geophys., 32, 363-403.
Moorthi, S., H.-L. Pan, P. Caplan, 2001: Changes to the 2001 NCEP operational MRF/AVN global analysis/forecast system. NWS Technical Procedures Bulletin, 484, pp14. [Available at http://www.nws.noaa.gov/om/tpb/484.htm].
Pacanowski, R. C. and S. M. Griffies, 1998: MOM 3.0 Manual, NOAA/Geophysical Fluid Dynamics Laboratory, Princeton, USA.
Saha, S., S. Nadiga, C. Thiaw, J. Wang, W. Wang, Q. Zhang, H. M. van den Dool, H.-L. Pan, S. Moorthi, D. Behringer, D. Stokes, M. Pena, S. Lord, G. White, W. Ebisuzaki, P. Peng, and P. Xie , 2006: The NCEP Climate Forecast System. J. Climate, 19, 3483-3517.
Smagorinsky, J. 1963: General circulation experiments with the primitive equations: I. The basic experiment. Mon. Wea. Rev., 91, 99-164.
Sundqvist, H., E. Berge, and J. E. Kristjansson, 1989: Condensation and cloud studies with mesoscale numerical weather prediction model. Mon. Wea. Rev., 117, 1641-1757.
Zhao, Q. Y., and F. H. Carr, 1997: A prognostic cloud scheme for operational NWP models. Mon. Wea. Rev., 125, 1931-1953.