Details of GFS Model Version used in ESRL/PSD Reforecast Project

The model used in the ESRL/PSD Reforecast Project is a version of the NCEP Global Forecast System (GFS; formerly called the Medium-Range Forecast Model, MRF) that was used operationally from January to June 1998 (Caplan et al 1997, Wu et al 1998 and references therein).

  • GFS initialization: These ensemble forecasts are initialized at 00 UTC each day. The control run was initialized from NCEP/NCAR Reanalysis data, while initial conditions for the other 14 ensemble members were produced from 7 pairs of bred modes.
  • Model output archive: A limited number of model forecast variables are saved at an interval of 12 hours.

Overview of 1998 GFS Model Configuration:

Process Information Reference
Horizontal Resolution T62
Vertical Resolution 28 sigmal levels (top at p=0)
Time Integration Semi-implicit, taking into account physics tendencies
Horizontal Diffusion Laplacian type Leith (1971)
Deep Convection Simplified Arakawa-Schubert Pan and Wu (1994)
Shallow Convection Vertical diffusion of heat and momentum in the upper boundary layer and lower free atmosphere Tiedtke (1983)
Short-Wave Radiation Lacis and Hansen (1974)
Long-wave radiation Fels and Scharzkopf (1975)
Topography Mean Orography
Clouds 3 levels of stratiform clouds, fractional coverage determined by quadratic function of layer RH

References

Caplan, Peter, John Derber, William Gemmill, Song-You Hong, Hua-Lu Pan, David Parrish, 1997: Changes to the 1995 NCEP Operational Medium-Range Forecast Model Analysis-Forecast System. Weather and Forecasting: Vol. 12, No. 3, pp. 581-594.
Fels, S. B. and M. D. Schwarztkopf, 1975: The simplified exchange approximation: A new method for radiative transfer calculations. J. Atmos. Sci., 32, 1475-1488.
Kalnay, E., M. Kanamitsu, R. Kistler, W. Collins, D. Deaven, L. Gandin, M. Iredell, S. Saha, G. White, J. Woollen, Y. Zhu, A. Leetmaa, B. Reynolds, M. Chelliah, W. Ebisuzaki, W. Higgins, J. Janowiak, K.C. Mo, C.Ropelewski, J. Wang, Roy Jenne, Dennis Joseph, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bulletin of the American Meteorological Society: Vol. 77, No. 3, pp. 437-472.
Lacis, A., and J. E. Hansen, 1974: A parameterization for the absorption of solar radiation in the earth's atmosphere. J. Atmos. Sci., 31, 118-133.
Leith, 1971: Atmospheric predictability and two-dimensional turbulence. J. Atmos. Sci., 28, 145-161
Pan, H.-L., and W.-S. Wu, 1994: Implementing a mass-flux convective parameterization package for the NMC Medium Range Forecast Model. Preprints, 10th Conf. on Numerical Weather Prediction, Portland, OR, Amer. Meteor. Soc., 96-98.
Tiedtke, M., 1983: The sensitivity of the time-mean large-scale flow to cumulus convection in the ECMWF model. Workshop on convection in large-scale models, ECMWF, 297-316.
Troen, I. B., and L. Mahrt, 1986: A simple model of the atmospheric boundary layer: Sensitivity to surface evaporation. Bound.-Layer Meteor., 37, 129148.
Wu, Wan-shu, Mark Iredell, Suranjana Saha and Peter Caplan, 1997: Changes to the 1997 NCEP Operational MRF Model Analysis/Forecast System. NCEP Technical Procedures Bulletin 443, available from http://www.nws.noaa.gov/om/tpb/indexb.htm, or the National Weather Service, Office of Meteorology, Programs and Plans Division, Silver Spring, MD, 20910.