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Re: GRIB Aggregation


The NARR is a reanalysis, so it don't have forecast times.  I would be a
simple 03 hr chain (00 hr fct time) spanning 26 years.

See an existing GDS subset aggregation:
This will give a sense for the nature of the beast.

The directory structure is set up as such:

Heres the TDS aggregation I set up while experimenting yesterday, on a
non-related dataset:

  <dataset name="OceanWinds Test Daily Aggregation"
      ID="test/dailyagg" urlPath="test/agg">
    <netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2";>
     <aggregation dimName="time" type="joinNew">
       <variableAgg name="wind" />
       <scan dateFormatMark="#yyyyMMdd"
suffix=".nc" />
       <scan dateFormatMark="#yyyyMMdd"
suffix=".nc" />
       <scan dateFormatMark="#yyyyMMdd"
suffix=".nc" />
     <variable name="time" orgName="time">
       <attribute name="long_name" value="Days"/>
       <attribute name="units" value="days since 1987-07-09" />

Would this automatically detect the source of data were GRIB rather than
NetCDF?  and it seems like you need to set the <scan> on each individual
directory... Doing so the way NARR is set up would create one chunky
configuration file.  Is there anyway to have this scan a pattern
(YYYYMM/YYYYMMDD) of directories?

I understand GRIB requires a certain amount of "supplemented" metadata
for complience.  Where do you enter this?


Ethan Davis wrote the following on 6/13/2006 1:21 PM:
> Hi Dan,
> Aggregation should work the same for GRIB as for netCDF files. The issue
> would be how your GRIB files are structured and how you want to
> aggregate them. Our GRIB files each contain one full model run (all
> parameters, all forecast times). We haven't tried aggregating beyond that.
> We have started tracking what is available for the NCEP models on our
> server. This is from the TDS 3.8 announcement (with links updated):
>    We also are now tracking detailed inventory of NCEP model output, eg:
> http://motherlode.ucar.edu:8080/thredds/modelInventory/model/NCEP/NAM/CONUS_12km/
>    These are all linked from the "collection dataset" pages; For
>    example from
> http://motherlode.ucar.edu:8080/thredds/catalog/model/NCEP/NAM/CONUS_12km/catalog.html
>    choose the top "CONUS_12_km" link, then choose "Available Inventory"
>    Documentation.
> One idea for this work is to eventually provide access to alternate
> datasets, for instance, a dataset that contains all the 3hr forecast
> times from the different runs, or one that contained all the 12Z valid
> times from the different runs. Tracking these detailed inventories is
> just the first step but aggregation and alternate groupings of the data
> is pretty interesting to think about.
> How are your GRIB files structured and what kind of aggregation where
> you thinking about?
> Ethan
> dan.swank wrote:
>> Hello,
>> I've been tinkering with the TDS aggregation capabilities and they work
>> quite well for NetCDF data, however, I can't seem to find anything in
>> the docs regarding aggregating GRIB.
>> We want to get The NARR dataset which we have here at NCDC-NOMADS on the
>> TDS.  It consists of hundreds of thousands of 50 Mb + GRIB files in a
>>   Just scouting for a quick answer here:
>> Is aggregating the NARR GRIB currently feasable with the current release
>> of TDS?  If so, do any docs exist which could give me a starting point?
>> Converting it to NetCDF will not be possible (volume).

Dan Swank <address@hidden>
NOMADS Project:  Software & Data Management
Contractor - STG, Incorporated
Veach-Baley Federal Building
151 Patton Avenue
Asheville, NC 28801-5001
Phone: 828-271-4007

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