Re: New Model Ag Service for TDS

• To: "dan.swank" <Dan.Swank@xxxxxxxx>, Ethan Davis <edavis@xxxxxxxxxxxxxxxx>
• Subject: Re: New Model Ag Service for TDS
• From: John Caron <caron@xxxxxxxxxxxxxxxx>
• Date: Tue, 15 Aug 2006 14:42:30 -0600

Hi Dan:

dan.swank wrote:

John:

I've tinkered with the new GRIB aggregation, made a few subsets.
I noticed some funky x/y coords in the data dump :
Y begins at -832.6982610175619 (?) and X @ -4226.1069969154705.
Noitced in the definition that the units are Kilometers...
(from what reference lat/lon ?)

These are projection coordinates, in "km on the projecction plane". The 
projection is defined by

  char Lambert_Conformal;
    :grid_mapping_name = "lambert_conformal_conic";
    :standard_parallel = 25.0; // double

following the CF-1 conventions. This is the projection contained in the GRIB 
file.

The particular client I used to access this (GrADS) cannot decern this
x/y spatial cooredinate.  It is expecting them as lambert grid relative
x[1:x] etc.

Not sure weither this is something that can be configured
with the aggregation, but it certainly would be nice to have the option
to use grid relative x/y coords.

sorry, I dont know what "grid relative x/y coords" are?

Other than this, I see the TDS handles the varying Z dimension
across variables quite well.  Does it still require the
files to be homogenous?  Or will it scan each one for the
forecast hour = <specified> header tag ~ and use that?

Yes thats the intention, to not need index homogeneity, but to use the times in 
the GRIB files and make it all work nicely. The GRIB files require another 
level of XML configuration, to make it all work. We are hoping to work closely 
with all to get this figured out, and ill explain in more detail then.

-Dan


Glenn.Rutledge wrote the following on 8/15/2006 8:50 AM:

Dan-
You have the lead with Steven to implement this new aggregation service
on your platform of choice.  This is one of the Web Services I spoke of-
and please make this #1 priority.  See msg below.  Glenn


Subject:        Forecast Model Run Collection Aggregation prototype available
Date:   Mon, 14 Aug 2006 18:02:05 -0600
From:   John Caron <caron@xxxxxxxxxxxxxxxx>
Organization:   UCAR/Unidata
To:     techies@xxxxxxxxxxxxxxxx, Steve Hankin <Steven.C.Hankin@xxxxxxxx>



An experimental new TDS service "Forecast Model Run Collection Aggregation" is 
available for poking at on the motherlode development server:

http://motherlode.ucar.edu:9080/thredds/catalog/fmrc/NCEP/NAM/CONUS_80km/catalog.html
 (or .xml)

This aggregates a collection of Forecast Model Runs (in this case the IDD NAM 
CONUS 80km runs), making it available as one dataset with a 2D time coordinate.

Then it creates various other logical datasets:

1) data from one run (what we already are used to)
2) data with the same forecast offset hour (eg all the 3 hour forecasts, from 
different runs)
3) data with a constant forecast date (eg all the data for 
2006-08-08T12:00:00Z, from different runs)
4) the "best" time series, taking the data from the most recent run available

This is not production-ready, so dont clobber it, but any testing and comments 
welcome.

--
Glenn K. Rutledge
Services Team Leader
Remote Sensing and Applications Division
NOMADS Project Manager
National Oceanic and Atmospheric Administration
National Climatic Data Center
Asheville NC 28801
Phone: (828) 271-4097
Fax: (828) 271-4328

NOMADS: http://nomads.ncdc.noaa.gov/