FNMOC 181 x 360 Monthly Mean Sea Level Pressure

Monthly averages of the FNMOC (Fleet Numerical Meteorology and Oceanography Center) 6-hourly analyzed pressure fields on a 1-degree global spherical grid.

Two data sets are available in this group:

• 1967 - present. (interpolated from native grid for 1967 - 1996)
• The grid size of the pressure field provided by FNMOC has changed over the years as follows:
  • 1967 - 1980 (available for the Northern Hemisphere only) - 63 x 63 polar steriographic projection
  • 1981 - 1996 (available globally) - 144 x 73 spherical projection
  • Nov 1996 - present (available globally) - 360 x 181 spherical projection
• In order to create a relatively consistent SLP time series, PFEL has created 360 by 180 (1-degree) interpolated 6-hourly pressure fields from the historical pressure files. The interpolation is a simple linear interpolation from the native grid (shown above). Monthly averages of these 6-hourly fields were created for 1967 - present and are updated monthly.
• Technical Details
  • In these files, the latitude/longitude stamp is located at the center of the 1-degree boxes (ie for a box with corners at 45N 150W, 46N 149W, the lat/lon given in the file is 45.5N, 149.5W.) On a Ferret "shade" plot the correct 1-degree squares will be filled. On a time series plot, Ferret will interpolate to the exact position the user specifies (to avoid this extra interpolation, users should enter coordinates at half degree intervals)
  • The monthly time stamp is centered in the middle of the month. On a time series plot this results in the correct behavior of centering the monthly points in the center of the averaging interval.


• Nov 1996 to present
• These data are the same as the above for Nov 1996 to the present with the following exceptions. Previously, FNMOC pressure fields have been distributed by PFEL on a 360 by 181 (1-degree) grid with the lat/lon stamps at the southwest corner of the boxes.(ie for a box with corners at 45N 150W, 46N 149W, the lat/lon given in the file is 45.0N, 149.0W), and the time stamps on the first day of the month. In order to provide consistency for users who have previously downloaded data, these data conform to these conventions.
• Technical Details
  • On a Ferret "shade" plot, the 1-degree squares that are shaded will be off by 0.5 degrees. On a time series plot, Ferret will interpolate to the exact position the user specifies, however, this position will still be the southwest corner of the 1-degree box.
  • Since the monthly time stamp is centered on the first of the month, on a time series plot the monthly points will be plotted at the beginning of the averaging interval.

For more information on the models used to compute these data please see:

Rosmond, T. E., 1992: A prototype fully coupled Ocean-Atmosphere Prediction System, Oceanography Vol. 5, No. 1, 25-30.

Clancy, R. M., 1992: Operational Modeling: Ocean Modeling at the Fleet Numberical Oceanography Center, Oceanography Vol. 5, No. 1, 31-35.