The preparation script removes data when a cdo command fails before

+ cdo -z zip_5 -mergetime u_GLOBAL1x1-1yr_6H_2023.nc.base u_GLOBAL1x1-1yr_6H_2023.nc.nextstep u_GLOBAL1x1-1yr_6H_2023.nc
cdo    mergetime: Open failed on >u_GLOBAL1x1-1yr_6H_2023.nc.nextstep<
                  No such file or directory
+ rm u_GLOBAL1x1-1yr_6H_2023.nc.base u_GLOBAL1x1-1yr_6H_2023.nc.nextstep