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NCEP GDAS (2.5 x 2.5 degree resolution)


General information about this dataset

  • The NCEP GDAS  (Global Data Assimilation System) analysis are available every 12 hours. 
  • Data are archived on a 2.5 degree x 2.5 degree lat/lon grid. 
  • Data are available from the mid 1970's to recent months (updated periodically). 
  • Through March 1997:
  • Beginning in April 1997:
  • Peculiarities/Caveats:
    • Northern and southern hemispheres of a given global field are archived as separate fields.
    • Snow-cover data are archived sporadically in the ON84 dataset.
    • SST are archived once per day in the ON84 dataset.

How to use this dataset with pregrid

  • ON84 GDAS
    • set SRC3D = ON84
    • The Vtables are set up automatically for the ON84 GDAS data set, but if you really want to see what they look like, see:  Sample Vtable for NCEP GDAS (ON84).
  • GRIB GDAS
    • set SRC3D = NCEP
    • The Vtables are set up automatically for the GRIB GDAS data set, but if you really want to see what they look like, see:  Sample Vtable for NCEP GDAS (GRIB).

Is this data available to ALL users

  • ON84 GDAS data is ONLY available to users with NCAR accounts
  • GRIB GDAS data for the last year is available to ALL users:
    • http://dss.ucar.edu/datasets/ds083.0/data/.
    • This data is kept current with the newest data added when available and data older than one year removed from the site.
    • To obtain the data, download from above web site

How to download data automatically

  • This option is only available to users with NCAR accounts
  • To obtain ON84 data for periods before April 1997,
    • use the script in REGRID/pregrid/on84/get_on84.csh
    • OR use the script available from ~mesouser/MM5V3/Util/get_on84.csh
  • To obtain the NCEP GRIB data (after April 1997),
    • use the script in REGRID/pregrid/ncep.grib/get_ncep.csh
    • OR use the script available from ~mesouser/MM5V3/Util/get_ncep.csh
  • When you run these scripts make sure that you work in a temporary directory (such as /tmp/$USER, or /ptmp/$USER on IBM).
  • Once you have downloaded the files from the MSS, you need to ftp the files to your local computer. All files must be transferred with the ftp "binary" mode.

How to download data manually

  • This option is only available to users with NCAR accounts
  • View the catalogs for the ON84 data and NCEP GRIB data
  • Find the data file name(s) from these online catalogs.
    • For example, from the inventory for NCEP GRIB data, you may find that the data file name (VSN number as they are referred to) for February 2000 is Y54804.
  • Log on to IBM
  • cd to /ptmp/$USER
  • type the following to obtain the data:
    • msread  -f BI  NCEP-Feb-2000-data  /DSS/Y54804
  • Move file NCEP-Feb-2000-data to where you are going to use it (remember if you are using ftp, move the file with "binary" mode).
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