[gradsusr] Loading GFS data (DODS) over nomad's ".ascii" option - how to read in grads?

[Arlindo da Silva]

On Tue, Sep 27, 2011 at 6:05 AM, Stauffer Reto (UNI) <
reto.stauffer at student.uibk.ac.at> wrote:

> Dear usergroup
>
> We would like to visualize some GFS products. Actually i get the data
> from the nomad servers "on demand" with
>
> 'sdfopen http://nomad3.ncep.noaa.gov:9090/dods/gfs20110927/gfs_master_00z'
>
> THE PROBLEM is that i have so much calls to the server that he kills the
> connection (after ~100 as written on the nomad3 servers page). Now there
> is also an option to load all the data with wget. For example the call is
>
>
> http://nomad3.ncep.noaa.gov:9090/dods/gfs20110926/gfs_master_00z.ascii?rh2m[14:28][46:46][22:22]
>
> It's the same "file/adress" but with the .ascii? option (selecting one
> variable "rh2m" here for certain timesteps [14:28] and for only one
> gridpoint (lon/lat 46/22). This works fine and i can create the
> ascii-file without any problem
>
>
I don't think this will make any difference in so far access restriction is
concerned. Using ASCII you likely just waste more resources than bringing
binary data. If I recall well these files are stored in GRIB-2 at the
server, so getting a single point may not save much because of the way
compression is implemented (it may still need to read a full lat/lon layer
in order to uncompress).


> BUT HOW TO READ those files with grads? Can i convert those files? Or
> open directly? Or create a controlfile?
>
> I read all possible hints and pages in the internet but i havnt found
> any solution until now.
> Does anyone have some experiences with that approach?
>
> Or is there another option not to run into the "server request
> restriction"?
>
>
What many people do is to grab the binary GRIB-2 files with wget using plain
http (not through the DODS interface). There are actually nice perl scripts
to automate this, see

   http://www.cpc.ncep.noaa.gov/products/wesley/fast_downloading_grib.html

For reading the GRIB-2 files, see Wes' utilities:

   http://www.cpc.ncep.noaa.gov/products/wesley/wgrib2/
   http://www.cpc.ncep.noaa.gov/products/wesley/g2ctl.html

and of course the grads documentation.

  Good Luck,

     Arlindo

-- 
Arlindo da Silva
dasilva at alum.mit.edu
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