Reading HDF-EOS files in GrADS

[Arlindo da Silva]

On Tue, Sep 22, 2009 at 3:36 PM, Aaron Pratt <aspratt2000 at yahoo.com> wrote:

> Hello,
>
> Is there a way to open HDF-EOS files in GrADS. I have tried to find
> information pertaining to this online, but have so far been unable to find
> anything. I would like to be able to open HDF-EOS formatted files from
> MODIS, CloudSat, CALIPSO, etc. (I believe HDF-EOS is the standard format
> for
> most of NASA's satellite data products.
>
>
HDF-EOS files are nothing more than HDF-4 files with additional metadata
added.  Format is not the issue here since GrADS can read HDF-4. The main
problem is that these files are not CF-1 (COARDS) compliant. For some Level
3 files, quantities are defined on a global 1x1 grid and a Data Descriptor
File (DDF)) can be written and the file opened with "xdfopen". However, most
Level 2 files are defined on swaths and such data structure is not currently
supported by GrADS. (I believe COLA has plans for supporting swath data in
the future, Jennifer may want to comment on it.)

   I have toyed with the idea of writing a GrADS extension for dealing with
swath data, but ended up using pyhdf in python for accessing such datasets.
On other situations, such as for EOS aerosol data (MODIS/MISR/OMI/PARASOL) I
have created my own grads readable version of datasets on the 1/4 deg GEOS-5
grid. Some of these are available on-line:

                       http://opendap.nccs.nasa.gov:9090/dods/AeroObs

  Good Luck,

        Arlindo



> Aaron Pratt,PhD
> NASA/ORAU Post-Doctoral Fellow
> Goddard Space Flight Center
> Greenbelt, MD 20774
>



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