How is the `output_interval` meta information in the output files used?

[guoqing-noaa]

The ufs-community version added the following code snippet to write out the output_interval meta information to output files.
It came from PR #18. It looks like NSSL added it.
Do we know how this information is used? Anyone uses this? Thanks!

MPAS-Model/src/framework/mpas_stream_manager.F

Lines 4304 to 4316 in dd7e157

	! Write output_interval to stream
	!
	IF (stream %filename_interval(1:4) /= "none") THEN
	call mpas_set_timeInterval(filename_interval, timeString=stream %filename_interval)
	call mpas_get_timeInterval(filename_interval,M=output_interval)
	call mpas_writeStreamAtt(stream%stream, 'output_interval',output_interval,syncVal=.true., ierr=local_ierr)
	if (local_ierr /= MPAS_STREAM_NOERR) then
	ierr = MPAS_STREAM_MGR_ERROR
	return
	end if
	END IF
	end if

[guoqing-noaa]

@ywangwof Do you have any information on how the output_interval meta information in the NetCDF output files is used? Thanks!

[ywangwof]

No. We did not add it. It may be inherited from an earlier version from the NCAR repository?

[guoqing-noaa]

@ywangwof Thanks for the information.
NCAR's repository does not have this.

[clark-evans]

@guoqing-noaa @ywangwof this code entered our repository through #18, where we merged with NSSL's then-current code. Fortunately, the branch associated with that merge is still active, so I was able to trace the code back. It came in two pieces:

On April 18, 2023, @ywangwof added the IF (stream %filename_interval(1:4) /= "none") THEN and END IF statements around the code in question:
jderrico-noaa@ca6c986

On March 29, 2023, Larissa originally added the code in question:
jderrico-noaa@6f80fb7

Larissa's commit message was Added "output_interval" from streams file as a global attribute to output files, but I'm not sure what use case motivated its addition.

[guoqing-noaa]

@clark-evans Thanks a lot for tracing this down to the source!!

@ywangwof Could you ask inside NSSL who has used or needs to use this output_interval meta information?
If no one uses it, I think we may remove this piece to align with the NCAR version. Thanks!