[CF-metadata] change_in

[Karl Taylor]

Dear all,

I think the distinction between "change in" a quantity (i.e., 
"delta-quantity"), and rate of change (i.e., "tendency" = 
delta-quantity/delta-t) should not be too difficult to explain without 
the use of "extensive" and "intensive".

I agree both should refer to "temporal" changes.

cheers,
Karl


Bryan Lawrence wrote:
> Hi Jonathan, Burkhardt et al
> 
> I'm not sure I like the idea of using change_in in this way. (Sorry I didn't 
> pick up the proposal idea in the earlier email ... Can someone explain to me 
> (possibly again) why this isn't a tendency of something due to advection? )
> 
> 1) I don't like the chances of people working with data appreciating the 
> difference between intensive and extensive variables. 
> 
> 2) Limiting the use of change_in in this way is non-intuitive, again, while
> we might want to define it that way, it may get used in other ways. Not now 
> perhaps, but ...
> 
> 3) Whether or not the thing is intensive or extensive should
> be independent of whether or not it is tendency otherwise we're complicating
> our vocabulary. If there we need to introduce a new qualifier that would be 
> cleaner ... 
> 
> Bryan
> 
> On Sunday 19 March 2006 16:29, Jonathan Gregory wrote:
> 
>>Dear Burkhardt
>>
>>
>>>is there any news or any decision on the "change_in_" issue?
>>
>>No-one expressed any view.
>>
>>Having thought about it a bit more, I think change_in_ is OK if it has the
>>same kind of uses as tendency_of. They are really the same except change_in
>>is extensive in time and tendency_of is intensive. They have the same
>>bounds in time. The units of tendency_of are X s-1 if change_in has units
>>X. We must be clear that change_in should *not* be used to describe every
>>possible kind of difference e.g. between locations or climates. It
>>specifically means the change in a quantity as a function of time. Do you
>>agree?
>>
>>Hence let us propose
>>change_in_atmospheric_water_content_due_to_advection (kg m-2)
>>
>>Best wishes
>>
>>Jonathan
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> 
>