User's Guide

NCEPIN

Convert a NCEP precipitable water (PWAT) transfer file to a LAS image

Function:

Convert a precipitable water product from National Center Environmental Prediction (NCEP) to a LAS image. The transfer file must have been extracted from the PWAT record of a GRidded Binary (GRIB) file.

Parameters:

TRANFILE
Transfer file extracted from the NCEP forecast file using the wgrib procedure. (See User Note 1)

OUT(--)
LAS output file

  1. LAS> ncepin tranfile="fnl_gdas1_pwat06_000507.trn" out=pwat05070006

    The transfer file fnl_gdas1_pwat06_000507.trn will be converted to LAS image pwat05070006.

  2. LAS> ncepin tranfile="fnl_gdas1_pwat18_000412.trn"

    The transfer file fnl_gdas1_pwat18_000412.trn will be converted to LAS image fnl_gdas1_pwat18_000412 since the parameter OUT was not specified.

Description/Algorithm:

The transfer file is first converted to a LAS image. Since the original values are stored as millimeters (kg/m^2) they are converted to centimeters. Next, the two halves of the image are swapped so that the final image is centered on 0 degrees longitude instead of 180 East. Finally the DDR is edited to reflect the correct projection information. Processing is done in the current directory.

Nonfatal Error Messages:

    None

Fatal Error Messages:

  1. [ncepin-mathdiv] Error occurred converting <XXXXX> to centimeters

    An error occurred while converting the values in image <XXXXX> to centimeters. Try running the procedure again. If the problem persists contact the system administrator.

  2. [ncepin-concat] Error occurred swapping left and right sides of <XXXXX>

    An error occurred in the CONCAT procedure. Try running the procedure again. If the problem persists contact the system administrator.

  3. [ncepin-editddr] Error occurred editing DDR of <XXXXX>

    An error occurred editing the DDR of image <XXXXX>. Try running the procedure again. If the problem persists contact the system administrator.

User Notes:

  1. The transfer file can be extracted from a GRIB file using the wgrib procedure found in ADAPSCONTRIB. The following commands should be used:

      set recnum=`$ADAPSCONTRIB/wgrib $infile -v | grep PWAT | awk -F: '{print $1}'`
      $ADAPSCONTRIB/wgrib $infile -d $recnum -ieee -o $tranfile