[CF-metadata] CF names / inherent optical properties in seawater

From: Jonathan Gregory <j.m.gregory>
Date: Tue, 29 Sep 2009 09:58:35 +0100

Dear John

> Does the radiation ever get accumulated over the range of wavelengths,
> for example, "Total visible radiation"? That seems quite different
> than totaling all the temperatures measured in an area, which is a
> discrete mathematical summation (or else is called by some other unit
> like 'heat energy'?). Would suggest the 'area' analogy doesn't apply
> well to wavelengths.

The difference is between intensive and extensive quantites, I think. The
existing "spectral" quantities have their units multiplied by m-1 because
they are per unit wavelength interval. These quantities are radiances, and
they are extensive in wavelength. That is, they are integrated over a
wavelength interval, and the value depends on how big the interval is. That's
like sea-ice volume in m3. The bigger the area you integrate over, the
bigger the volume.

The attenuation coefficients proposed by Frederic are intensive quantities
wrt wavelength interval. They are more like an average over the interval
concerned. They do not necessarily get bigger for a wider interval. I suggest
they don't need to say "spectral" just because they depend on wavelength,
any more than "temperature" needs to indicate in its standard name what
coordinates it depends on. The attenuation coefficients are more like
temperature, or sea-ice thickness in m, which are intensive wrt area.

Best wishes

Jonathan
Received on Tue Sep 29 2009 - 02:58:35 BST