[gradsusr] CMIP5 and GrADS

[Jennifer Adams]

Dear All, 
I will be giving a presentation at the AMS meeting next week on strategies I've used to download CMIP5 data. It's kind of a technical talk, maybe only of interest to a few members of this forum, but there is one slide that is relevant for GrADS (the text is below). I've done a bit of scripting to automatically generate descriptor files (for 'xdfopen' and 'open' when PDEF is necessary). The script parses the list of data files to determine the range of time steps for a particular variable and then generates the relevant CHSUB entries. It also does some other data-management checking to make sure the files cover a continuous, non-overlapping time span. Other functionality is listed below under the first bullet. I also have some code that will create PDEF files for non-rectilinear grids. ESMF's RegridWeightGen tool and a custom C program I wrote to translate the weights into a PDEF file make this a relatively easy job, allowing GrADS to handle a lot of data that were previously inaccessible. Although these scripts were all written for CMIP5 data, they can be adapted for other data sets. At some point, I'd like to bring some of this code under the hood of GrADS, but that is still a bit far off… In any case, please let me know if you are interested in any of my scripts -- it seems a shame to spend so much time developing code for only one person to use.
--Jennifer


•Create GrADS descriptor files
	Aggregate files over time dimension
Make use of ensemble dimension when appropriate
Identify missing or overlapping time periods
Assign non-standard dimensions 
   (e.g. basin averages or fixed fields)
Handle 365_day calendars
• Create PDEF files for non-rectilinear grids
For ocean and sea ice realms
ESMF’s RegridWeightGen utility generates the
   interpolation weights
Vector fields must be rotated from grid-relative 
   to Earth-relative coordinates before interpolation


--
Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at cola.iges.org



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