Model Details
The model used is a version of the NCEP Medium-Range Forecast Model (MRF) that was used in operations from January to June 1998 (Caplan et al 1997, Wu et al 1998 and references therein). More recent versions of the MRF are not compatible with the initial condition files available with the reanalysis. An overview of the model formulation is presented in the table below. The control run was initialized with the NCEP/NCAR Reanalysis (Kalnay et al 1996) once per day at 00 UTC and run forward 21 days. Output was saved every 12 hours.
The model code and sample scripts will be availabe for download soon.
| Process |
Information |
Reference |
| Horizontal Resolution |
T62 |
|
| Vertical Resolution |
28 sigmal levels (top at p=0) |
|
| Time Integration |
Semi-implicit, taking into account physics tendencies |
|
| Horiz. 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.