Dear Jonathan,

Thanks for these clarifications. 

> > 1. Is there a standard name for "diurnal temperature range", or a combined 
> > standard name/cell method representation? Cf. the 2010 mail archive thread 
> > http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2010/054016.html that 
> > added "range" to Appendix E.

> The cell_method of range was approved in ticket 65
> http://cf-trac.llnl.gov/trac/ticket/65
> and will be added in CF 1.7, which is under preparation. You could use this, 
> in combination with time bounds, to describe a diurnal range.

To make sure that I understand: the standard name is "air_temperature", and for 
monthly mean the cell method is "time: range within days time: mean over days"
But how about common continentality indices based on the annual range of 
monthly mean temperatures? 
Is there a "within months" such that the cell method for the basic element of 
the continentality index would be "time: mean within months time: range within 
years" ? Or is there another solution?


> > 3. Several of the standard names directly targeted at climate indices (e.g. 
> > "spell_length_.....", "number_of_days_...") are dimensionless because the 
> > unit is already included in the standard name. This is of course consistent 
> > and parsimonious in terms of describing the data. But with respect of a 
> > software package producing a plot that needs a legend with units attached, 
> > it is not very enlightening to have the unit "1". For example, in a map of 
> > Frost Days the title drawn from the long name or the comment may be 
> > something like "Number of Frost Days (Tmin < 0 degC)" but the color scale 
> > should preferably have units "days" rather than "1".  As this is not 
> > specific to climate indices, what is the CF accepted advice or solution to 
> > this?

> The spell_length variables have canonical units of days. The number_of_days 
> variables have canonical units of 1, as you say. This is logical. Could you 
> use the standard name, including the phrase "number_of_days", to derive the 
> appropriate label?

Yes, of course we could come up with something along those lines, or maybe add 
an attribute. I just thought there might be a widely used solution that I did 
not know of.

Best wishes,
Lars



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