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

From: Thomas Lavergne <thomasl>
Date: Mon, 27 Oct 2008 09:19:20 +0000

Hi Jonathan,
>> eastward_sea_ice_displacement [m] (length of [lon0,lon1] on Earth
>> surface)
>> northward_sea_ice_displacement [m] (length of [lat0,lat1] on Earth
>> surface)
>> sea_ice_x_displacement [m] (length from P0 to P1, taken along
>> the grid's X axis)
>> sea_ice_y_displacement [m] (length from P0 to P1, taken along
>> the grid's Y axis)
>> sea_ice_displacement [m] (the length [P0,P1] on Earth surface)
>> direction_of_sea_ice_displacement [degrees] (the direction to North of the
>> [P0,P1] vector)
>
> These all look good to me. I agree that "displacement" conveys the idea of
> moving from A to B. 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.

Good you agree with the chosen terms :-)!
Does it mean I can safely use those standard names and claim CF compliance? Will they be added to
the list of standard names?

This issue does not only arise for sea ice. 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. 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?

Is see two (complementary) ways:
1) report values on the displacement itself, using the variables cited above. Then I need a way to
indicate the start and the end time (which might not be homogeneous across one file);
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...

Any hints, thoughts or reference for me?

Cheers,
Thomas
Received on Mon Oct 27 2008 - 03:19:20 GMT