Modify naming and attributes of time variables on history files to be consistent with other CESM components #554

[phillips-ad]

These changes are being requested to improve the ease-of-access of CESM data and to normalize the look of the metadata across CESM components. See ESCOMP/CESM#194 and especially the google doc referenced from ESCOMP/CESM#194 (comment).

Current CAM time array output:

double time(time) ;
	time:long_name = "time" ;
	time:units = "days since YYYY-MM-DD HH:MM:SS" ;
	time:calendar = "noleap" ;
	time:bounds = "time_bnds" ;
double time_bnds(time, nbnd) ;
	time_bnds:long_name = "time interval endpoints" ;

Proposed CAM time array output:

double time(time) ;
	time:long_name = "time" ;
	time:units = "days since YYYY-MM-DD HH:MM:SS" ;
	time:calendar = "noleap" ;
	time:bounds = "time_bounds" ;
double time_bounds(time, nbnd) ;
	time_bounds:long_name = "time interval endpoints" ;
	time_bounds:units = "days since YYYY-MM-DD HH:MM:SS" ;
	time_bounds:calendar = "noleap" ;

Changes made: time_bnds renamed as time_bounds, added units/calendar attributes to time_bounds, change bounds attribute of time to time_bounds

@billsacks @phillips-ad @strandwg are filing similar issues for each component.

[gold2718]

This request (arising from ESCOMP/CESM#194?) mentions time and time_bnds ⇒ time_bounds.
What about the related variables in CAM history files?

• date (int, "current date (YYYYMMDD)")
• datesec (int, "current seconds of current date")

Does anyone use these fields? Do they need to match time? @phillips-ad? @billsacks? @nusbaume?

[nusbaume]

@gold2718 I am not aware of any current usage for date and datesec in the ADF, but I'll ping that group to see if anyone uses those fields in general, and if it would be beneficial for them to have it match time.

[phillips-ad]

@gold2718 that's a great catch. I for one do use the date variable as no conversion is necessary to read it (using ncdump for example). Yes, if we shift time to the center of the averaging period, date/datesec also needs to be shifted to align with the centered time. I will add this to #159.