I think Jonathan had got it right.
> If the sensor is 200 m above the sea-floor, its standard name should
> be sea_water_pressure, not sea_water_pressure_at_sea_floor. It would
> need a coordinate variable or scalar coordinate variable with a value
> of 200 m and a standard name of height_above_sea_floor (which is an
> existing standard name).
I'd apply this to instruments ON the sea floor too, though, with the value
of height_above_sea_floor set to 0.
> However, I think that if it's on the sea-floor we should put that in
> the standard name. ... A conceptual reason for this is that
> quantities on particular physically important surfaces often do have
> somewhat different physical uses or interpretations from quantities
> on surfaces defined by coordinate variables in the body of a fluid.
The main distinction, as far as data use, is not whether the instrument is
ON the sea floor, but whether it's at a fixed distance from it. If it is
at a known distance from the sea floor, the pressure measurements are
useful as a 'dynamically important quantity' while if it is at a known
distance from the surface, the pressure data is an indicator of mooring
motion.
Almost nothing, other than an anchor, is really placed ON the sea
floor, at least not on purpose. It would be tricky to draw the line (1
meter? less?) and would make it easy to overlook usable data when
compiling comparable data sets with sea floor and/or fixed near-floor
mounts.
Cheers (and, thanks!)
- Nan
--
*******************************************************
* Nan Galbraith (508) 289-2444 *
* Upper Ocean Processes Group Mail Stop 29 *
* Woods Hole Oceanographic Institution *
* Woods Hole, MA 02543 *
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Received on Fri Sep 05 2008 - 08:42:27 BST
