source: TOOLS/INTERP_NUDGE/interp_from_era.ksh

#!/bin/ksh
set verbose echo
#
# This script will interpolate horizontaly ERA-I
# output to the desired model grid 
#
# Contact Josefine Ghattas
###############################################################################
###############################################################################
###############################################################################
# BEGIN USER DEFINITION
###############################################################################

# gridfile : file grilles_gcm.nc containing longitudes and latitudes of the destination grid
gridfile=/ccc/store/cont003/dsm/p86ghatt/IGCM_OUT/LMDZ/ELI-144x142x79/ATM/Output/Grid/ELI-144x142x79_1979_grilles_gcm.nc

# indir : path for directory containing the files to interpolate
#indir=/u/rech/psl/rpsl376/ERAI/NETCDF/GLOBAL_075/4xdaily/AN_PL
indir=/ccc/work/cont003/subipsl/subipsl/ERAI/NETCDF/GLOBAL_075/4xdaily/AN_PL/
# insuffix : suffix in input files
insuffix=.aphei.GLOBAL_075.nc

# varlist : list of variables to interpolate
varlist="u v ta r"

# Variables for output :
# outdir : directory to store output files
outdir=$WORKDIR/NUDGEFILES/ERAI-144x142x79
# outsuffix : suffix to output files
outsuffix=_erai.nc

# Time variables :
# first_year : first year to interpolate
first_year=1979
# last_year : last year to interpolate
last_year=2016

# Frequency of output files : yearly or monthly
# OutFreq='monthly' or OutFrequ='yearly'
OutFreq='yearly'
 
# rundir : temporary run directory
rundir=`pwd`/rundir
echo rundir=$rundir

###############################################################################
# END USER DEFINITION
###############################################################################
###############################################################################
###############################################################################
if [ ! -d ${rundir} ] ; then
    mkdir -p ${rundir}
fi
cp -f era2gcm.ksh $rundir/.
cd $rundir

###############################################################################
# For all variables do :
#   1) Interpolate all month and years for each variable
#   2) Add a time step last in each file coming from next month 
###############################################################################
# Loop over all variables
for var in $varlist ; do
    year=$first_year
    month=01

    # 1 - Loop over all files and interpolate the variable
    while [[ ${year} -le ${last_year} ]] ; do
        # Create output directory if it does not exist
        if [ ! -d $outdir/${year} ] ; then
            mkdir -p $outdir/${year}
        fi

        # Define source and target file
        filein=${indir}/${year}/${var}.${year}${month}${insuffix}
        fileout=${outdir}/${year}/${var}_${year}${month}${outsuffix}

        # Interpolate filein and save in fileout
        echo Interpolate file $filein and save in file $fileout
        ./era2gcm.ksh $gridfile $filein tmp.nc $var
        mv tmp.nc $fileout
        echo


        # Find next month and year
        case $month in
            12)
                nextyear=`expr $year + 1`
                nextmonth=01
                ;;
            *)
                nextyear=$year
                nextmonth=`expr $month + 1`
                if [[ $nextmonth -le 9 ]] ; then
                    nextmonth=0$nextmonth
                fi
                ;;
        esac
        # Update month and year
        year=$nextyear
        month=$nextmonth
    done


    # Do different treatement if monthly or yearly output files are wanted
    if [[ $OutFreq = 'monthly' ]] ; then
      # 2 - Loop over all files and add a time step : 
      #     take the first time step from next coming month and add last in current month
      echo Before add step

      year=$first_year
      month=01
      while [[ ${year} -le ${last_year} ]] ; do
        # Find next month and year
        case $month in
            12)
                nextyear=`expr $year + 1`
                nextmonth=01
                ;;
            *)
                nextyear=$year
                nextmonth=`expr $month + 1`
                if [[ $nextmonth -le 9 ]] ; then
                    nextmonth=0$nextmonth
                fi
                ;;
        esac
        
        file=${outdir}/${year}/${var}_${year}${month}${outsuffix}
        nextfile=${outdir}/${nextyear}/${var}_${nextyear}${nextmonth}${outsuffix}
        if [ -f ${nextfile} ] ; then
            echo First time step from file ${nextfile} will be added last in file ${file}
            cp -f $file file.nc
            cp -f $nextfile next.nc
            ncks -O -d TIME,0,0 next.nc tmp.nc
            ncrcat -O file.nc tmp.nc tmptot.nc
            mv tmptot.nc $file
        else
            echo Next file ${nextfile} does not exist. Nothing will be done for ${file}
        fi

        # Update month and year
        year=$nextyear
        month=$nextmonth
      done

    elif [[ $OutFreq = 'yearly' ]] ; then
        # 3a. Concate the monthly files into yearly files
        mkdir -p  ${outdir}/allyears
        
        year=$first_year
        while [[ ${year} -le ${last_year} ]] ; do
        echo Now merge year=$year for variable $var
            cdo mergetime ${outdir}/${year}/${var}_${year}* ${outdir}/allyears/${var}_${year}${outsuffix}
            year=`expr $year + 1`
        done

        # 3b.Add a last timestep in the end of the yearly files from next coming year
            year=$first_year
            while [[ ${year} -le ${last_year} ]] ; do
              # Find next month and year
              nextyear=`expr $year + 1`
                
              file=${outdir}/allyears/${var}_${year}${outsuffix}
              nextfile=${outdir}/allyears/${var}_${nextyear}${outsuffix}
              if [ -f ${nextfile} ] ; then
                 echo First time step from file ${nextfile} will be added last in file ${file}
                 cp -f $file file.nc
                 cp -f $nextfile next.nc
                 ncks -O -d TIME,0,0 next.nc tmp.nc
                 ncrcat -O file.nc tmp.nc tmptot.nc
                 mv tmptot.nc $file
              else
                 echo Next file ${nextfile} does not exist. Nothing will be done for ${file}
              fi

              # Update month and year
              year=$nextyear
          done
    fi
    
# End of loop variable list
done

### Copy gridfile in output dir
cp -f $gridfile $outdir/grilles_gcm.nc
    
exit