[CF-metadata] Optical properties

From: Jonathan Gregory <j.m.gregory>
Date: Mon, 19 Sep 2005 20:54:07 +0100

Dear Pepe

Thanks for your clarifications by email. Please see my responses below. You
asked what is the formal procedure for adding names: it is to make proposals as
you have, so they can be discussed on the email list. So far we haven't got a
rule for how long we must leave for comments to be made. This is an aspect of
CF governance, for which we need procedures, now that CF is becoming widely
used. I hope that we will decide these procedures within the next few months.
What is also obvious is that we need people to work on CF. The CF authors such
as me have very little "spare" time from our "proper" occupations! It is
no-one's job, and it should be, so that development can proceed fast enough to
meet the growing needs. We are trying to secure resources for this.

In this case, I propose that these names be added on Monday 3rd October, if
you are happy and no-one else raises objections before then.

Best wishes

Jonathan


>- Lw: Water Leaving Radiance

I propose we add these:

surface_upwelling_spectral_radiance_in_sea_water:W m-2 m-1 sr-1
surface_upwelling_radiance_in_sea_water:W m-2 sr-1

The first is what you asked for, but the second might be needed too. There are
downwelling versions of these quantities in the table already.

>- CDOM: Chromophoric Dissolved Organic Matter

Since this is actually an absorption coefficient like those requested by
Michael Godin, I think we should call it

volume_absorption_coefficient_of_radiation_in_sea_water_due_to_dissolved_organic_matter:m-1

This is a bit long, unfortunately, but would be consistent. I don't think we'd
need to specify "chromophoric" because dissolved organic matter that doesn't
absorb light would not contribute anyway.

>- TSM: Total Suspended Matter

You have described this as a concentration (kg m-3) rather than a content
(kg m-2) so I propose

concentration_of_suspended_matter_in_sea_water:kg m-3

>- Kd (Diffusive Attenuation Coefficient)

Your explanation suggests to me that this is the same as what Michael Godin
has requested:

volume_attenuation_coefficient_of_radiation_in_sea_water:m-1

You say "diffusive" means that it applies to diffuse light, but is that
actually a significant distinction? Is the attenuation coefficient different
for direct beam and diffuse illumination?

>- alpha: Angstrom Exponent

The term NASA (for instance) uses is

aerosol_angstrom_exponent:1

>- Aerosol optical thickness

To be clear which layer it applies to I think we need both

atmosphere_optical_thickness_due_to_aerosol:1
optical_thickness_of_atmosphere_layer_due_to_aerosol:1

In the latter case, a coordinate variable would define the layer boundaries.
Wavelength dependence would be indicated by adding a coordinate variable in
radiation_wavelength.
Received on Mon Sep 19 2005 - 13:54:07 BST