Climate Data Operators (CDO) snippets

Raúl Valenzuela

Last updated on May 18, 2022 1 min read python

CDO is a suit of command line tools to operate and edit NetCDF and grib files. Here are some snippets that I use the most. In addition, NCO is a similar suit of tools but dedicated to NetCDF only. The snippets are implemented in Bash, so that the operation is executed in a set of files.

Add the values of two variables located in their own files

for i in $(seq 1979 1979); do
  echo $i
  cdo -b F32 enssum ./crr/era5_convective_rain_rate_$i.nc ./lsrr/era5_large_scale_rain_rate_$i.nc ./trr/era5_total_rain_rate_$i.nc;
done

Crop a latlon box

for i in $(seq 1979 2018); do
  echo $i
  cdo sellonlatbox,-73,-69.75,-36.25,-32.5 ./trr/era5_total_rain_rate_$i.nc ./trr_box/era5_total_rain_rate_$i.nc;
done

Replace the name of variables and their long_name (which is an attribute)

for i in $(seq 1979 2018); do
  echo $i
  cdo chname,crr,trr ./trr_box/era5_total_rain_rate_$i.nc ./trr_box/era5_total_rain_rate_$i.nc;
  ncatted -a long_name,trr,o,c,"Total rain rate" -O ./trr_box/era5_total_rain_rate_$i.nc ./trr_box/era5_total_rain_rate_$i.nc;
done

Extract precipitation (in m to mm) from a grid point and put output in a csv file

cdo -outputtab,date,lon,lat,value -remapnn,lon=-70.75_lat=-34.25 -mulc,1000 era5_tp_daily_2000.nc > ofile.txt

snippets cr2 python