[gradsusr] merra data

[Molin Antoine]

Hi,

Thanks for your answer.

I tasted your cooking, and it is good; but we would like to get the 
MERRA data at the resolution 2/3 ° x 0.5°.

So i downloaded the Merra data, hdf files, with the variables SLP, U50m, 
V50m and T2m.

* the variable SLP is not recognized by Grads!  (the variable "SLP" is 
on the Merra site: 
http://disc.sci.gsfc.nasa.gov/daac-bin/FTPSubset.pl?LOOKUPID_List=MAT1NXSLV)

* i tried first to read a hdf file with xdfopen, but the written ddf 
(enclosed file) is not good; a "SDF_dimension_name" is lacking, i think, 
for TDEF; but how do you name this dimension_name? and how do you scan a 
hdf file?

Thanks, and best regards.
Antoine Molin





Le 30/09/2011 22:17, Arlindo da Silva a écrit :
> On Fri, Sep 30, 2011 at 4:22 AM, Molin Antoine 
> <antoine.molin at poweo.com <mailto:antoine.molin at poweo.com>> wrote:
>
>
>     Dear All,
>
>     For wind energy in France, i would like to use Merra data; it is
>     in fact rather easy to get daily files from the Nasa (enclosed
>     file:hourly wind speeds at 50m for one day, NetCDF).
>     But then?
>     Could you tell me how you would:
>     * aggregate the daily files: do you use "template"
>
>
> Yes.
>
>     * read the aggregate files (i think we need a descriptor file and
>     use xdfopen or open under grads, isn'it?; or is it better to work
>     with HDF files?).
>
>
> Using a template makes it easier to work with the HDF files.
>
>     * best way to eventually create the descriptor file
>
>
> Yes, it should be sufficient to create a DDF file with 3 records: 
> DSET, OPTIONS template, and TDEF. Please read the User's Guide:
>
> http://grads.iges.org/grads/gadoc/SDFdescriptorfile.html
>
> Now, depending on the extent of data analysis you need to perform it 
> may be practical for use to access MERRA data directly through 
> OPeNDAP. In fact, we have made the whole MERRA collection on-line. 
> There are a number of recipes in the Cookbook explaining how to work 
> with MERRA data, click on this link: 2.6.1 NASA/GSFC MERRA 
> <http://cookbooks.opengrads.org/index.php?title=Table_of_Contents#NASA.2FGSFC_MERRA>
>
> The opengrads bundle also ships with a GUI interface for browsing the 
> MERRA datasets, see
>
> http://cookbooks.opengrads.org/index.php?title=Recipe-016:_Accessing_MERRA_data_with_a_Graphical_User_Interface
>
> Just type "merra" on the command line; under Windows you should have a 
> MERRA icon on your desktop.
>
>     Arlindo
>
>
>
>
>
> -- 
> Arlindo da Silva
> dasilva at alum.mit.edu <mailto:dasilva at alum.mit.edu>


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