ncfloortrace

#!/bin/tcsh

## This script takes a "trace" threshold and sets values below that
## threshold to zero.  The threshold is recorded in an attribute named
## "trace_threshold".

## The conventional meteorological definition of "trace precipitation"
## is less than 0.01 inches.  Because this program uses truncation
## instead of rounding, it's best to use a slightly smaller threshold.
## For LWE (thickness) units (mm or inches), a threshold of 0.001 is
## recommended.  For MKS units (kg/m^2/s), a threshold of 1e-7 is
## recommended.  (1e-7 kg/m^2/s = 0.00864 mm/day)

if ($#argv < 1 || $#argv > 4) then
    echo "Usage: ncfloortrace threshold infile [outfile [varname]]"
    echo "Set netcdf variable values below threshold to zero."
    echo ""
    echo "  outfile defaults to infile"
    echo "  varname defaults to first component of input filename,"
    echo "    as delimited by . or _"
    echo ""
    echo "Recommended threshold values for precipitation: "
    echo "  1e-7 for MKS units (kg/m^2/s)"
    echo "  0.001 for LWE/thickness units (mm or inches)."
    exit
endif

set theta = $1


set infile = $2


if ($#argv > 2) then
   set outfile = $3
else   
   set outfile = $infile
endif


if ($#argv > 3) then
   set var = $4
else   
   set var = `basename $infile | cut -f 1 -d _ | cut -f 1 -d .`
endif


ncap2 -s 'where('$var' < '$theta') '$var' = 0;' $infile $outfile

ncatted -h -a trace_threshold,$var,o,d,$theta $outfile


# Copyright 2010-2012 Univ. Corp. for Atmos. Research
# Author: Seth McGinnis, mcginnis@ucar.edu