[CF-metadata] Sea water transparency and reflectance.

From: Jonathan Gregory <j.m.gregory>
Date: Mon, 19 Oct 2009 18:04:04 +0100

Dear Olivier

> *About reflectance, the quantity that is usually provided in ocean
> colour products is the bidirectional reflectance; albedo is of the
> same nature than reflectance, except that it is integrated on all
> directions.

I see, thanks.

> In CF there is `toa_bidirectional_reflectance', which is quite closed
> to the quantity we are looking for. [Philippe and ocean colour people,
> of course please tell me if I'm wrong]
>
> Then I would suggest to turn my first proposal into
> `surface_bidirectional_spectral_reflectance': with "surface" instead
> of "toa", and adding "spectral" because this field is provided at
> several wavelengths. Do you agree?

I don't think you need "spectral", which is a word we use to indicate that
the quantity is per unit wavelength or frequency. The TOA bidirectional
reflectance also depends on wavelength (see its definition) and you specify
the wavelength with a coordinate variable. So I would suggest simply
surface_bidirectional_reflectance.

Do you also need standard names of angle_of_incidence and angle_of_reflection
to use for those independent (coordinate) variables on which the reflectance
depends?

> **About Secchi disk
>
> Yes the intention is primary to provide the depth in meters. So I'd
> prefer something closed to your second suggestion, like
> "secchi_depth_of_sea_water".

Fine. It is not self-explanatory, but that is not always attainable, and at
least it indicates that it's a property of sea water, which should be useful
to the user of the data.

Best wishes

Jonathan
Received on Mon Oct 19 2009 - 11:04:04 BST