Hi Roy-
While the NCDC NOMADS is a TDS provider (
http://nomads.ncdc.noaa.gov/thredds/catalog.html); we are not now
providing Ocean models - however NODC is currently planning an
"Ocean-NOMADS". Scott Cross is cc:ed herein. I believe that the Marine
Modeling group is engaged in this discussion as well. Scott and Co,
could use some user input I'm sure. Jordan Alpert tells me Avichal
Mehra at NCEP will soon be standing up the OPeDNAP (gds) access to the
RTOFS on the NOMADS server at NWS: http://nomads.ncep.noaa.gov/
Glenn
Rich Signell wrote the following on 1/29/2009 7:40 AM:
Roy,
Good thing you asked because we spent some time last summer scratching
our heads over this one with the folks from NCEP!
The RTOFS GRIB files represent an interesting case indeed, and the
solution again shows the power of NcML. It also shows that we need a
version of the THREDDS Data Server that uses NetCDF-Java 4.0.
The problem is that RTOFS is a general curvilinear orthogonal grid
(see http://coast-enviro.er.usgs.gov/models/share/2009-01-29_0717.png)
that is not uniformly spaced in any map projection that can be
specified analytically -- there is no GRIB code that can be used to
determine the X,Y locations of the curvilinear grid cells. The RTOFS
GRIB files specify "204", which was unknown to the NetCDF-Java 2.2.22,
so it just stopped with an "unknown projection = 204" error. But
with NetCDF-Java 4.0, it recognizes 204 as a
"Curvilinear_Orthogonal_Grid". If you check out the NcML view of a
RTOFS variable from the NetCDF tools app (-java -Xmx512m -jar
toolsUI-4.0.jar), here's what you see:
<variable name="Sensible_heat_net_flux" shape="time y x" type="float">
<attribute name="units" value="W m-2" />
<attribute name="long_name" value="Sensible heat net flux @
surface" />
<attribute name="missing_value" type="float" value="-9999.0" />
<attribute name="grid_mapping" value="Curvilinear_Orthogonal_Grid" />
<attribute name="GRIB_param_discipline"
value="Meteorological_products" />
<attribute name="GRIB_param_category" value="Temperature" />
<attribute name="GRIB_param_name" value="Sensible_heat_net_flux" />
<attribute name="GRIB_param_id" type="int" value="2 0 0 11" />
<attribute name="GRIB_product_definition_type"
value="Analysis/forecast at horizontal level/layer" />
<attribute name="GRIB_level_type" type="int" value="1" />
</variable>
Of course, you still want to provide CF-compliant data via OpenDAP to
your users, and the magic of NcML allows you to just union in a file
that containst the lon and lat variables. So Avichal Mehra at NCEP
kindly provided the lon/lat values and we made a NetCDF file that just
contained those variables called "rtofs_lonlat.nc
<http://rtofs_lonlat.nc>". So the NcML looks like:
<netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2";>
<aggregation type="union">
<netcdf location="shtfl.grib2"/>
<netcdf location="rtofs_lonlat.nc <http://rtofs_lonlat.nc>"/>
</aggregation>
<variable name="Sensible_heat_net_flux">
<attribute name="coordinates" value="lon lat"/>
<remove type="attribute" name="grid_mapping"/>
</variable>
<attribute name="Conventions" type="String" value="CF-1.0"/>
</netcdf>
If you want to try this out, you can grab these files (including grib
and NcML) from:
http://coast-enviro.er.usgs.gov/models/share/rtofs.zip
Unfortunately, while the NcML works with NetCDF-Java 4.0, the current
THREDDS Data Server does not yet use NetCDF-Java 4.0. As a work
around for THREDDS using NetCDF-Java 2.22, you could modify ASCII .gbx
file that get created when NetCDF-Java reads a grib file, replacing
the unknown 204 code with something like "30". This will allow
NetCDF-Java to continue without error, and it doesn't matter because
the grid_mapping is not being used anyway.
-Rich
On Wed, Jan 28, 2009 at 4:09 PM, Roy Mendelssohn
<Roy.Mendelssohn@xxxxxxxx <mailto:Roy.Mendelssohn@xxxxxxxx>> wrote:
Hi All:
Can THREDDS serve the RTOFS grib files? We are getting an error
of unsupported coordinate system, get similar error within
toolsUI. Is here something we need to ad to the setup to get it
to work?
Thanks,
-Roy
**********************
"The contents of this message do not reflect any position of the
U.S. Government or NOAA."
**********************
Roy Mendelssohn
Supervisory Operations Research Analyst
NOAA/NMFS
Environmental Research Division
Southwest Fisheries Science Center
1352 Lighthouse Avenue
Pacific Grove, CA 93950-2097
e-mail: Roy.Mendelssohn@xxxxxxxx <mailto:Roy.Mendelssohn@xxxxxxxx>
(Note new e-mail address)
voice: (831)-648-9029
fax: (831)-648-8440
www: http://www.pfeg.noaa.gov/
"Old age and treachery will overcome youth and skill."
"From those who have been given much, much will be expected"
--
Dr. Richard P. Signell (508) 457-2229
USGS, 384 Woods Hole Rd.
Woods Hole, MA 02543-1598
--
Glenn K. Rutledge
Meteorologist / Physical Scientist
Team Lead
Data Access Branch
Climate Services Division
NOMADS Project Manager
National Oceanic and Atmospheric Administration
National Climatic Data Center
151 Patton Ave
Asheville NC 28801
Phone: (828) 271-4097
Fax: (828) 271-4876
NOMADS: http://nomads.ncdc.noaa.gov/
