NPP: Download GDAS cron script

download_gdas.sh

#! /bin/bash

#
# This script downloads all gdas1.PGrbF00.*.*.z of previous day or
# whichever day specified by '-d' options given to 'date' command
# into current directory.
#
# Download GDAS of a specific day using '-d' option of date command.
#
# The Global Data Assimilation System (GDAS) files are required
# by VIIRS TrueColorGen algorithm
#

set -e

if [ -t ]; then
	verbose='--verbose'
else
	verbose='--no-verbose'
fi

# Download GDAS of previous day by default
if [ $# -eq 0 ]; then
	yymmdd=$(date +'%y%m%d' '-d yesterday')
else
	yymmdd=$(date +'%y%m%d' "$@")
fi

for hour in "00" "06" "12" "18"; do
    # Only download newer files
	wget $verbose -N ftp://is.sci.gsfc.nasa.gov/ancillary/temporal/global/gdas/gdas1.PGrbF00.${yymmdd}.${hour}z
done