- General Notes
1. General Notes
Latitude-longitude points on the native grid for the Atlantic RTOFS model
are on a curvilinear orthogonal
grid. The latitude-longitude point files for correct
interpretation of the data files as well as other data files and software
for processing Atlantic RTOFS data is available
README and the
Readme.RTOFS files for more information on the files and software.
Vertical coordinates are interpolated to 40 fixed-depth
positions, as specified here.
The operational data file format is
GRiB (GRIdded Binary). Additional information on the use of GRiB at NCEP is
To work with Atlantic RTOFS GRiB, any standard tools which read GRiB will work. One
such tool is the freely available wgrib utility.
The wgrib home page and software is here.
Another free GRiB file reader is the read_grib utility that can
decode GRiB data directly into MATLAB (MATLAB is a registered trademark of The Mathworks,
We realize that many users of Atlantic RTOFS output may be more familiar with
NetCDF (network Common Data Form).
This is not a format available from NCEP operational systems.
To convert GRiB to netCDF, you will need a utility such at
Source code for gribtonc is available
as part of the UNIDATA decoders package.
To build the converter to work with the large Atlantic RTOFS files, you will need to
change the file grib1.h in decoders-3.1.2/src/gribtonc/
- Change :
- #define MAX_GRIB_SIZE 200000
- #define MAX_GRIB_SIZE 2000000
- Then build and install as instructed.
The netCDF files are approximately 6 times the size of the GRiB files, up to
1.2 GB for a netCDF file containing a single 3-dimensional field as compared
to 250 MB in a GRiB file containing all available fields.
You will need the lat-long files described in the
General Notes. You may need the file
ofs3z.cdl to carry out the conversion as gribtocdl does not generate a
The NOMADS (NOAA Operational Model Archive Distribution System) data server offers daily full-fields and
hourly surface fields. The server can be accessed at
http://nomads6.ncdc.noaa.gov/ncep_data/index.html, and offers interactive
graphics as well as direct data downloads and DODS/OpenDAP access.
More information on NOMADS is available
DODS/OpenDAP client software can be found