New capabilities in reading GRIB files with NCL

From: Mary Haley (haley AT XXXXXX)
Date: Mon Jan 27 2003 - 10:03:30 MST

  • Next message: ENOMOTO Takeshi: "JMA GRIB"

    To users of GRIB files:

    Since Enomoto Takeshi brought up an NCL/GRIB question, I thought it
    would be a good time to announce some major upgrades we've made to
    NCL's GRIB reading capability. These capabilities will be available in
    the next minor release of NCL (version 4.2.0.a028, a few weeks away),
    but a beta version is available now if you want to test it. (See
    details below.)

    Here are some of the new capabilities and changes:

        The ability to load GRIB parameters from a file has been
        added. This can be done by setting the environment variable
        NCL_GRIB_PTABLE_PATH to a file or directory path. Parameter tables
        read from a file have precedence over built-in tables that would
        otherwise apply to the same dataset. An interface for adjusting
        this precedence at run-time is on the enhancement request list.
        
        Many new built-in parameter tables were added, including all files
        supported by wgrib (http://wesley.wwb.noaa.gov/wgrib.html), three
        Forecast Systems Laboratory tables, and a Navy Fleet Numerical
        Meteorology and Oceanography Center table. Support was also added
        for thinned "quasi-regular" grids.
        
        The way NCL names certain GRIB variables has been changed. This
        may result in variable names that are incompatible with previous
        names. In particular, variables involving average, accumulation,
        and difference over specific periods of time. For example, the
        variable "PRATE_GDS4_SFC_ave" will now be
        "PRATE_GDS4_SFC_ave6h". This was required because some GRIB files
        have averages for several differing periods on the same file.
        
        A problem was fixed for parameters less than 128 in ECMWF files.
        
    If you are interested in helping us to beta test these new
    capabilities, please send me email (haley@ucar.edu) and let me know
    what kind of system you have. We will send you more information about
    these new capabilities and a binary to try.

    Or, if you like, you can provide us with GRIB files to test.

    We appreciate your feedback and help on this!

    Cheers,

    --Mary Haley
      NCL Project Coordinator
      NCAR/SCD/VETS
      1850 Table Mesa Drive
      Boulder, CO 80305
      haley@ucar.edu
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