[gradsusr] CMIP5 and GrADS

[Jennifer Adams]

Hi, Jim -- 
I will not be re-distributing the CMIP5 data I have collected via OPeNDAP. I believe some of the ESGF data nodes are putting their data behind LAS, and I guess since all the data are behind a THREDDS server you could access individual files with a URL, but I don't know how the authentication works in either case. In any event, the volume, complexity, granularity, and wide distribution of the data make OPeNDAP access a bit awkward and slow, and I have not pursued it as means for looking at CMIP5 data. 
--Jennifer




On Jan 6, 2013, at 10:17 PM, James T. Potemra wrote:

> Jennifer:
> 
> I'm curious whether you will be distributing the processed model output via an OPeNDAP server?  Or maybe someone knows of one already?  Thanks,
> 
> Jim
> 
> On 1/4/13 2:00 PM, Jennifer Adams wrote:
>> 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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--
Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at cola.iges.org



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