[CF-metadata] Standard name(s) needed for satellite-based ice drift?products

From: Jonathan Gregory <j.m.gregory>
Date: Thu, 30 Oct 2008 17:27:08 +0000

Dear Thomas

> Does it mean I can safely use those standard names and claim CF compliance?
> Will they be added to the list of standard names?
Not yet. The procedure is that it is left open to discuss for a while on this
email list. Alison Pamment, the manager of standard names, will summarise the
discussion (if any) and make an announcement when new standard names are going
to be included in the table. The next scheduled update is 11 Nov.

> Clouds, water masses do move
> and this motion might sometimes be measured/reported as "displacement" when
> the time rate of measurements does not allow direct interpretation as
> velocity
Yes. If people want to record data like that, they could propose corresponding
standard names to yours.

> And as you mention, displacement implies not one but *two*
> reference times (one for the start and one for the end of the period). Is
> there a chapter/section in the CF convention dealing with how to
> report/format such 'displacement' data?

I was trying to get at that when I said this:

> >A displacement would be extensive in time, and the time
> >bounds would record the two measurement instants between which the
> >displacement occurred. By contrast, a velocity is intensive in time.

but I was not clear. Time coordinates have bounds in CF i.e. each "point" in
time has a coordinate, which lies within an interval, and the ends of the
interval are recorded as the time-bounds. An extensive variable (like
displacement) would have a cell_methods entry of "TIME: sum", where TIME is
the name of the time-coordinate. An intensive variable (like velocity) is
most often a mean, with is indicated with "TIME: mean". That's probably still
not clear enough! This is describe in Sect 7.1, 7.2 and 7.4 of CF.

> 2) report 'states' at start and end time. The 6 values latStart, lonStart,
> timeStart, latEnd, lonEnd and timeEnd indeed completely describe the
> displacement. So we could imagine a 2 dimensional time array
> (timeBounds[1,n]=timeStart[n], timeBounds[2,n]=timeEnd[n],
> lat[1,n]=latStart[n], etc...). But I am a bit worried about how tools used
> for visualization might interprete a time varying lat/lon fields...

I assumed your displacement fields were (lat,lon) and gave some values
representative of cells fixed in space. A completely different approach is
to record the trajectory. That can be described in CF in a different way,
in Sect 5.5.

Cheers

Jonathan
Received on Thu Oct 30 2008 - 11:27:08 GMT