[CF-metadata] RE: agreed standard names

From: Jonathan Gregory <j.m.gregory>
Date: Sat, 5 Nov 2005 19:49:17 +0000

Dear Pepe

Thanks for your email. Unfortunately I don't understand the distinctions you
are making! Please could you help again with this.

volume_attenuation_coefficient_of_downwelling_radiation_in_sea_water:m-1
> Kd - Diffuse Attenuation Coefficient
> volume_attenuation_coefficient_of_downwelling_irradiance_in_sea_water:m-1
> This is important since Kd is a measure of 'irradiance' attenuation and not
> of 'radiation'
We haven't used the word "irradiance" in standard names. "Irradiance" means
radiative flux (per unit area). I assumed that the attenuation coefficient of
radiation could not refer to anything other than radiative flux or something
proportional to it. Is there another possible interpretation?

> CDOM - Colour Dissolved Organic Matter
> volume_absorption_coefficient_of_radiation_in_sea_water_due_to_coloured_dissolved_organic_matter:m-1
> This is important since it is only the 'coloured' component which we are
> interested in.
What does "coloured" mean? Perhaps it means having a wavelength-dependent
attenuation coefficient? i.e. are you excluding absorption which does not
change the colour of incident white light?

I notice that you don't propose that this "radiation" should be changed to
"irradiance"/"radiative flux" - what's the difference from the last point?

surface_upwelling[_spectral]_radiance_in_air_reflected_by_sea_water:W m-2 sr-1
> Lr -
> surface[_spectral]_sky_radiance_in_air_reflected_by_sea_water: W m-2 m-1
> sr-1
> This clarification is important since from your proposed name it seemed that
> Lr was a measure of the reflected scattered radiation but Lr is instead a
> measure of the reflected sky radiance.
>From what Mike said I understood Lr to be the portion of the upwelling
radiation which came from reflection by the sea-water surface of downwelling
radiation. The remainder of the upwelling radiation is that which comes out
through the surface of the sea water. Are you making a further distinction
between "sky" and other downwelling radiation? I'm not sure which "scattered"
radiation you are referring to.

> is the CF policy to use only SI units ? I am asking this since some
> quantities are never expressed in SI units.

The units stated in the standard name table are "canonical" units. Any unit
which is dimensionally equivalent (SI or not) is acceptable. See section 3.3
of the CF standard.

Best wishes

Jonathan
Received on Sat Nov 05 2005 - 12:49:17 GMT