pr2prec

#!/bin/tcsh

## This script converts netcdf files with precipitation in mass flux
## units (kg m-2 s-1) to LWE thickness units (mm/day).  Water has a
## density of 1 gram per cubic centimeter and one kilogram of water
## spread out over a 1-meter square forms a layer one millimeter deep,
## so to perform this conversion, we just multiply by 60*60*24 seconds
## in a day.  Only the first precip variable found is converted.

## The variable name is determined by grepping the input file header
## for a variable with the appropriate units for conversion.

## Replacment standard name is constructed by prepending "lwe_" and
## changing "flux" to "rate" on the existing filename.  This should be
## correct in most cases.

## If no output filename is specified, a default filename is
## constructed by substitution on the input filename as follows:

##    s/pr/prec/

## The resulting output file is placed in the same directory
## as the input file.

set prog = `basename $0`

if ($#argv < 1 || $#argv > 2) then
    echo "Usage: $prog infile [outfile]"
    exit 1
endif

set infile = $1

if ($#argv == 2) then
    set outfile = $2
else
    set outfile = `dirname $infile`/`basename $infile|sed -s 's/pr/prec/'`
endif


set v = `ncdump -h $infile | grep units | grep '= \"kg m-2 s-1\"' \
         | head -1 | cut -f 1 -d : | awk '{print $1}'`

if ($v == "") then
    echo ${prog}: no precip variable found with units = \"kg m-2 s-1\"
    exit 2
endif

set sname = lwe_`ncdump -h $infile | grep "$v\:standard_name" \
                 | cut -f 2 -d \" | sed -s s/flux/rate/`

ncap2 -O -s "$v=$v"'*(60*60*24)' \
  -s $v'@standard_name="'$sname'"' \
  -s $v'@units="mm/day"' \
  $infile $outfile

ncrename -v $v,prec $outfile

ncatted -h -a tracking_id,global,o,c,`uuidgen` $outfile

# Copyright 2010-2018 Univ. Corp. for Atmos. Research
# Author: Seth McGinnis, mcginnis@ucar.edu