example6.rst

Example 6. Convert fields from grid point GRIB ERA data into UM grid netCDF file

#! /usr/bin/env convsh

#  Convsh script era2um.tcl
#
#  Convert ERA grid point surface data into data on the UM climate grid.
#  Output format is netCDF. For example:
#
#      era2um.tcl -i gpsf90122600 -o gpsf.nc

#  Write out netCDF file
set outformat netcdf

#  Automatically work out input file type
set filetype 0

#  Convert PMSL, 2m T fields in input files to netCDF on UM 96x73 grid
set fieldlist_p "3 6"
#  Convert 10m u and v fields in input files to netCDF on UM 96x72 grid
set fieldlist_u "4 5"

#  Get command line arguments:
#      -i input files (can be more than one file)
#      -o output file (single file only)

set i false
set o false
foreach arg $argv {
   switch -glob -- $arg {
      -i      {set i true ; set o false}
      -o      {set i false ; set o true}
      -*      {puts "unknown option $arg" ; set i false; set o false}
      default {
         if {$i} {
            set infile [lappend infile $arg]
         } elseif {$o} {
            set outfile [lappend outfile $arg]
         } else {
            puts "unknown option $arg"
         }
      }
   }
}

if {! [info exists infile]} {
   puts "input file name must be given"
   exit
}

if {[info exists outfile]} {
   if {[llength $outfile] > 1} {
      set outfile [lindex $outfile 0]
      puts "Only one output file can be specified, using $outfile"
   }
} else {
   puts "output file name must be given"
   exit
}

#  Read in each of the input files

foreach file $infile {
   readfile $filetype $file
}

#  Set up 96x73 grid
set nx 96
set x0 0.0
set dx 3.75
set ny 73
set y0 90.0
set dy -2.5
#  Transform to a regular grid
setgridtype regular
#  Define x-axis
setgrid 1 $nx $x0 $dx
#  Define y-axis
setgrid 2 $ny $y0 $dy

#  Interpolate data from 320x160 Gaussian grid to UM 96x73 grid
interp_grid $fieldlist_p

#  Set up 96x72 grid
set nx 96
set x0 1.875
set dx 3.75
set ny 72
set y0 88.75
set dy -2.5
#  Transform to a regular grid
setgridtype regular
#  Define x-axis
setgrid 1 $nx $x0 $dx
#  Define y-axis
setgrid 2 $ny $y0 $dy

#  Interpolate data from 320x160 Gaussian grid to UM 96x72 grid
interp_grid $fieldlist_u

#  Write out all input fields to a single netCDF file

writefile $outformat $outfile [concat $fieldlist_p $fieldlist_u]