Post-processing concatenates new file to old.

Hi,

While I have been trying to post process surface fluxes for a007 and m02j I stumbled upon this issue: if I rerun some postprocessing for a given number of ensemble members, the postprocessing adds the new file to an old one, resulting to a file that has for example 20 ensemble members. Now I manually check each and every file to make sure it has the correct number of ensemble members. My atm diagnostics is /home/eexarchou/atmosphere_diagnostics/nccf_atm_monthly.sh and it is the master branch.

Any advice of how to deal with this is welcome!

Cheers Eleftheria

ps: people who could be interested in this are @cprodhomme @vguemas @pabretonniere @obellprat