Many diagnostic options may be enabled during a single run of MOM. Each one writes data to a filename which is unique to the particular diagnostic. For instance, data from diagnostic option snapshots will be written to a filename containing the keyword ``snapshots'' while data from option tracer_averages will be written to a filename containing the keyword ``tracer_avg''.
Within a given diagnostic, if data is written as unformatted 32 bit IEEE, then the output filename is given the suffix yyyyyy.mm.dd.dta. If data is written in NetCDF format, then the output filename is given the suffix yyyyyy.mm.dd.dta.nc. The ``yyyyyy.mm.dd'' is a place holder for the year, month, and day information. The purpose of this infomation is to allow for easy file management using UNIX.
If option separate_diag_files is enabled, the year, month, and day correspond to the timestep during which the diagnostic data was written. If the interval for saving data results in multiple datasets being written during one run, then each dataset will have a distinct filename (i.e. same keyword name but different date information). If option separate_diag_files is not enabled, the year, month, and day information in the filename will correspond to the last timestep of the run. So multiple datasets written out for a particular diagnostic during a single run will all be appended to one filename.
Since data from options time_step_monitor and trajectories are typically written out very often within a model run, both options write to a filenames which corresponds to the last timestep of the run.