#152: Time mean over area fractions which vary with time
-----------------------------+------------------------------
Reporter: martin.juckes | Owner: cf-conventions@…
Type: enhancement | Status: new
Priority: medium | Milestone:
Component: cf-conventions | Version:
Resolution: | Keywords:
-----------------------------+------------------------------
Comment (by jonathan):
Dear Martin and Karl
I suppose that the sentence "The interpretation more generally ..." in
Karl's text applies to the particular cell_method concerned, not to the
entire cell_methods attribute. if that is so, it doesn't contradict
Martin's statement, which I agree with, about different methods for
different dimensions. It would be good to clarify this by specifying this
remark replies to an entry in the attribute. Also, I find the phrase "when
area is not the only dimension to which is applies" rather confusing. I
''guess'' this phrase is there because if the cell method is about `area`
it surely must be area-weighted, so it's redundant rather than wrong - is
that the idea, Karl? If it is, I think we could omit it. I suggest running
together this paragraph and the preceding one in Karl's new text, as
follows:
An entry in the `cell_methods` attribute with the form "`area: mean where`
''type1'' `over` ''type2''" indicates the mean is calculated by
integrating over the ''type1'' portion of the cell and dividing by the
area of the ''type2'' portion. When "`over` ''type2''" is omitted, it is
assumed to be the same as ''type1''. When the "where" construct is used,
the interpretation is that a "weighted" mean is reported. Specifically,
the quantity of interest is integrated over all dimensions associated with
the method with weights proportional to the fraction of ''type1''
area_type that exists, and then this is divided by the integral over the
same dimension(s) of the fraction of ''type2'' area_type that exists.
Best wishes
Jonathan
--
Ticket URL: <http://cf-pcmdi.llnl.gov/trac/ticket/152#comment:15>
CF Metadata <http://cf-convention.github.io/>
CF Metadata
