Navy Operational Global Atmospheric Prediction System
(NOGAPS 4.0)

Basic equations: Primitive equations with hydrostatic approximation
Independent variables: Latitude, longitude, hybrid pressure coordinate, sigma levels
Dependent variables: Vorticity, divergence, virtual potential temperature, specific humidity, surface pressure, ground temperature, ground wetness and cloud fraction
Numerical techniques: Horizontal spectral differencing, second-order finite difference in the vertical, and central time differencing with Robert semi-implicit corrections
Integration domain: Global, surface to 1 mb
Horizontal resolution: T239 (~0.50 degree on the Gaussian grid)
Vertical levels: 30 sigma levels with approximately 6 sigma levels below 850 mb, depending on terrain elevation
Forecast time: 144 h from the 0000, 0600, 1200 and 1800 UTC ops run
Initial fields: Machenhauer initialization of increments from the U.S. Navy Atmospheric Variational Data Assimilation System (NAVDAS).
First-guess fields: Previous NOGAPS 6-h or 12-h forecast
Orography: Spectrally truncated and Lanczos filtered mean heights from the USGS Global Land One-kilometer Base Elevation (GLOBE) database.
Horizontal diffusion: Linear, fourth-order LaPlacian for vorticity, divergence and temperature.
Moisture physics: Convective precipitation (Emanuel), shallow cumulus mixing (Tiedtke) and large-scale convection.
Radiation: Long-wave and short-wave radiation (Harshvardhan) computed every 2 hour.
Gravity wave drag: (Webster et al.)
Planetary boundary layer: (Louis)
Land surface: Single layer/bucket model
Ocean surface: Sea surface temperature and ice coverage percentage from U. S. Navy NCODA.

History of Hemispheric and Global Atmospheric Model Development at FNMOC and NRL:

1959- Quasi-geostrophic 500 mb/thickness advection 500mb (barotropic)
1970- Northern Hemisphere Primitive Equation (NHPE) (63 x 63/L5)(baroclinic)
1975- NH/SH PE (63 x 63/L5)
1982- NOGAPS 1.0 (4.0 x 5.0/L6)
1983- NOGAPS 2.0 (2.4 x 3.0/L6)
1983- NOGAPS 2.1 (2.4 x 3.0/L9)
1987- NOGAPS 2.2 (2.4 x 3.0/L9)
1988- NOGAPS 3.0 (T47/L18/2.5 degree)
1989- NOGAPS 3.1 (T47/L18/2.5 degree)
1989- NOGAPS 3.2 (T79/L18/1.5 degree)
1992- NOGAPS 3.3 (T79/L18/1.5 degree)
1994- NOGAPS 3.4 (T159/L18/0.75 degree)
1998- NOGAPS 4.0 (T159/L24/0.75 deg)

NOGAPS Parameterization Improvements Since 1998:

JAN 1999

- Increase surface roughness for land points to better represent the effects of valleys and ridges

APR 1999

- Improve sea-ice latent heat release, resulting in slightly decreased evaporative flux

JUN 2000

- Replace the Relaxed Arakawa-Schubert cumulus parameterization with Emanuel cumulus parameterization

SEP 2000

- Increase stratospheric diffusion, resulting in reduced SH stratospheric jets

SEP 2000

- Implement higher resolution terrain fields from NIMA DTED Level 1 terrain database

DEC 2000

- Change cloud parameterization, better representing coastal and Arctic stratus, leading to reduced Arctic warm bias and increased tropical lower level winds

MAR 2001

- Improve vertical diffusion and Emanuel cumulus convection, better estimating initial heat flux and reducing upper level tropical temperature warm bias

MAY 2001

- Improve Emanuel cumulus convection, making the vertical profile of mixing cloud mass flux a function of buoyancy rather than buoyancy gradient, further reducing upper level tropical temperature warm bias

JUN 2002

- Update Emanuel convective scheme, adjusting specific heat of liquid-ice phase to reduce upper level heating, and selecting convection source level to maximize buoyancy at LCL, improving cloud base mass flux

JUL 2002

- Set a minimum snow depth for perpetually snow-covered regions (Greenland and Antarctica), to counteract the model tendency of melting off during extended absences of snow data

SEP 2002

- Increase NOGAPS resolution to T239/L30/0.5 degree

JUL 2003

- Convert NOGAPS from 64-bit to 32-bit, except for matrix inversion.

JUL 2003

- Improve matrix inversion module

SEP 2003

- NAVDAS data assimilation system operational

NOV 2003

- Implement terrain fields from USGS Global Land One-kilometer Base Elevation (GLOBE) database.

NOV 2003

- Change gravity wave drag scheme to Webster et al.

Additional reading:

"The Design and Testing of NOGAPS", Rosmond, T. Weather and Forecasting, Vol. 7, No. 2, June, 1992.

"The Navy Operational Global and Regional Atmospheric Prediction System at the Fleet Numerical Oceanography Center", Bayler, G. and H. Lewit. Weather and Forecasting, Vol. 7, No. 2, June, 1992.

"North Pacific Cyclone Sea-Level Pressure Errors with NOGAPS", Harr, P., R. Ellsberry, T. Hogan and W.Clune. Weather and Forecasting, Vol. 7, No. 3, October, 1992.

"Sensitivity Studies of the Navy's Global Forecast Model Parameterizations and Evaluation of Improvements to NOGAPS", Hogan, T. and L. Brody. Monthly Weather Review, Vol. 121, No. 8, August, 1993.

"Numerical Weather Analysis and Forecast Evaluations at Fleet Numerical Meteorology and Oceanography Center", Clune, W. Naval Meteorology and Oceanography Command News, Part I, Vol. 13, No. 8, August, 1993; Part II, Vol. 14, No. 2, February, 1994.

"Impacts of the Extra-Tropical Transition of Tropical Cyclones on Mid-Latitude Circulation Systems (in NOGAPS)", Harr, P., R. Ellsberry, P. Klein, T. Hogan and W. Clune. Fifteenth Conference on Weather Analysis and Forecasting, American Meteorological Society, August, 1996.

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Last Update Was On March 8, 2004