Re: Gribtonc changes

• To: Jim Cowie <cowie@xxxxxxxx>
• Subject: Re: Gribtonc changes
• From: Robb Kambic <rkambic@xxxxxxxxxxxxxxxx>
• Date: Thu, 29 May 2003 11:17:16 -0600 (MDT)

On Tue, 27 May 2003, Jim Cowie wrote:

Hi Robb,

Here's my $0.02:

1) GRIB2 support - you didn't mention this but I really hope that support
    for GRIB2 is included. Last I heard, the NWS is going to start using
    this before too long.

Hiya Jim,

Yes there will definitely be grib2 support.  I'm actually working on this
now.

2) The biggest problem we have with gribtonc is that all the product
    tables are hard-coded. We often get grids from FSL or elsewhere
    which don't use the NCEP grib tables, so we have to modify the code.
    Externalizing this to a set of (optional) tables would solve this
    problem.

Yea, hard coding tables is bad.  Actually I've been working on making XML
files of all the tables. So far, I've got more than 25 tables. The tables
are located at:

http://www.unidata.ucar.edu/projects/THREDDS/tech/index.html#STD

I would like to hear comments about the tables.


Robb...

-jim



Robb Kambic wrote:
> Hiya,
>
> I'm writing to inform you about some proposed changes to the output
> netCDF files produced by the gribtonc (GRIB-to-netCDF) decoder.  There
> are about 35 sites that have installed the decoders package as far as I
> know.  I'm currently in the process of updating the package, including
> the CDLs to make them more useful and to add attributes required by
> new conventions.
>
> The original CDLs followed the NUWG conventions:
>
>   http://www.unidata.ucar.edu/packages/netcdf/NUWG/
>
> which haven't been modified in several years,
>
> Lately the CF conventions
>
>   http://www.cgd.ucar.edu/cms/eaton/cf-metadata/index.html
>
> are becoming established as a more complete set of conventions for
> model output.  Also, we are considering including spatial and temporal type
> variables to make the NetCDF file more GIS compatible.  Another idea is to
> enhance the metadata about the date for THREDDS servers and other NetCDF
> clients.
>
> The CDL variable names will continue to follow the NUWG conventions
> for backward capability. The long_name attribute has been standardized
> by concatenation of the NUWG variable name plus the NUWG level name
> using the word "at" as a connector. So, the T_trop long_name is
> "Temperature at tropopause" in all the CDLs.  This supports
> consistency in applications such as Unidata's IDV (Integrated Data
> Viewer). For similar reasons, we are adding attributes required by
> other conventions such as CF, such as the standard_name attribute.  A
> sample variable will look like:
>
>         float  T_trop(record,y,x) ;
>                T_trop:long_name = "Temperature at tropopause" ;
>                T_trop:standard_name = "air_temperature" ;
>                T_trop:units = "degK" ;
>                T_trop:GRIB_parameter_number = 11 ;
>                T_trop:GRIB_level_flag = 7 ;
>                T_trop:_FillValue = -9999.f ;
>                T_trop:navigation = "nav" ;
>
>
> Some other additions to the variable attributes are the GRIB_parameter_number,
> and the GRIB_level_flag attributes. These are being included so other
> conventions may refer to the NCEP GRIB tables as a cross reference.  This will
> permit more flexible usage for the NetCDF files.
>
> Another variable has been added called forecast_time, a human readable
> string representing the valid forecast times. To make the  data
> monotonically increasing, the code sets records for all the valid times in the
> netCDF file on initialization.
>
> When netCDF GIS applications become available, the new NetCDF files
> will already have the needed information for correct display. We are also
> considering temporal variables so time bounding boxes can be created for the
> datasets.
>
> This is a brief summary of the kind of modifications we are making to
> the decoders package.  If you have other ideas about what should be
> included or omitted, please send in your comments.
>
>
> Robb...


--
Jim Cowie
NCAR/RAP
cowie@xxxxxxxx
303-497-2831

==============================================================================
Robb Kambic                                Unidata Program Center
Software Engineer III                      Univ. Corp for Atmospheric Research
rkambic@xxxxxxxxxxxxxxxx                   WWW: http://www.unidata.ucar.edu/
==============================================================================

• References:
  • Gribtonc changes
    • From: Robb Kambic