NOGAPS

Last Updated: Tuesday, 15-Jul-2008 11:05:08 PDT

The acronym NOGAPS has been used since 1982 to represent the Navy’s global numerical weather prediction system, which includes components for data quality control, data assimilation, model initialization, and model forecasts. While the nature of the components has changed considerably over the years, NOGAPS has been and remains the central engine that is the heart of the Navy’s environmental prediction capability. NOGAPS provides forcing fields for mesoscale weather prediction; tropical cyclone prediction; aerosol prediction; ocean, wave, and ice prediction; and aircraft and ship routing applications. NOGAPS also forms the backbone of the Navy’s ensemble prediction system, which provides global forecasts out to 10 days.

Continually improving the components of NOGAPS has been an ongoing research and development project over the years and many significant changes have been made to the system since it was first implemented. This historical development is documented in two short articles, one from 1998 and one from 2002. NOGAPS has also proven itself to be a valuable research tool, and the system is actively being used in basic research to increase our understanding of global dynamics, air/sea interaction, and atmospheric predictability.

History of NRL Global Model Resolution

Early modeling efforts
1959- 500 mb Quasi-geostrophic barotropic model for thickness and height
1970- N. Hemisphere Primitive Equation Model (63x63 grid points/5 levels)
1975- Added S. Hemisphere PE Model (63 x 63 grid points/5 levels) for first global coverage

Implementation of global UCLA-based model with a Successive Corrections Analysis scheme
1982- NOGAPS 1.0 (4.0º x 5.0º/L6)
1983- NOGAPS 2.0 (2.4º x 3.0º/L6)
1983- NOGAPS 2.1 (2.4º x 3.0º/L9)
1987- NOGAPS 2.2 (2.4º x 3.0º/L9)

Implementation of global Spectral model with a Multivariate Optimum Interpolation Analysis scheme
1988- NOGAPS 3.0 (T47/L18) ~ 2.50º horizontally
1989- NOGAPS 3.1 (T47/L18) ~ 2.50º horizontally
1989- NOGAPS 3.2 (T79/L18) ~ 1.50º horizontally
1992- NOGAPS 3.3 (T79/L18) ~ 1.50º horizontally
1994- NOGAPS 3.4 (T159/L18) ~ 0.75º horizontally
1998- NOGAPS 4.0 (T159/L24) ~ 0.75º horizontally
2002- NOGAPS 4.1 (T239/L30) ~ 0.50º horizontally

History of NOGAPS Skill

A common metric used by operational forecast centers to measure global model forecast skill is the anomaly correlation; a correlation of 0.6 typically represents a forecast that has some practical skill. As you can see from the chart below, while some years are clearly more predictable than others, the NOGAPS forecasts show an overall upward trend in skill at all forecast times, with the most dramatic improvements seen in the 5-day forecasts.

The Future of NOGAPS

Several exciting developments are on the horizon for NOGAPS, including a new variational data assimilation scheme planned for 2003 implementation and continued improvements to the model’s physics. More revolutionary changes include working with the NRL Space Science and Remote Sensing Divisions to extend NOGAPS much farther up into the atmosphere, to include all of the stratosphere and the mesosphere. We are also extending downward, by coupling NOGAPS to a global ocean data assimilation system. Finally, we are experimenting with finite element grids to examine their potential to form the basis of a new dynamical core for global modeling and possibly even a unified global/mesoscale prediction system.