When you are missing model output in your archive there is most of the time no need to rerun the simulation but only the post processing.

1) First check if the original model output is still there.

If the output is still there you will find it under the directory specified in ${CLIMAT_outrep}:

     ${CLIMAT_outrep}/${GEM_exp}/cfg_0000/firststep_*/???-???/*
resp.:
     ${CLIMAT_outrep}/${GEM_exp}/cfg_0000/laststep_*/???-???/*

If the data are neither in your archive nor in the above directories you will have to rerun the month.

2) If the original output is still under the above directories

Check if the post processing job still exists:

      ~/delayed_jobs/${TRUE_HOST}/${GEM_exp}_DX_*