[CF-metadata] new standard names for surface aerosol optical properties

From: Jonathan Gregory <j.m.gregory>
Date: Mon, 21 May 2012 18:20:31 +0100

Dear Markus

Your summary is clear and helpful for me, as a non-expert:

> CF aerosol variable names so far use the terms "_due_to_ambient_aerosol" and
> "due_to_dry_aerosol". For variables with "_due_to_ambient_aerosol", a
> co-ordinate variable relative_humidity is required since most aerosol
> properties are strongly dependent on particle humidification, and not taking
> this effect into account would render any model-observation comparison
> meaningless. The observations of surface aerosol optical properties I'm
> concerned with are intended to be on the dry aerosol. In some locations
> however (e.g. in the tropics), sample drying can be incomplete at times,
> leaving the sample in a state between ambient and dry. For this reason, I
> proposed a subset of variables with "_due_to_aerosol", also requiring a
> co-ordinate variable relative_humidity.

This makes sense to me, and I could agree to it, but it might be less than
ideal because due_to_aerosol does not say anything about the state of the
aerosol. If we say nothing, it might be misunderstood to be aerosol in any
state at all, not necessarily with RH specified, even though the details would
be clear in the description if they were consulted. It is generally more
helpful to say something when we can in the standard name, I think, to avoid
misunderstanding. For instance, would due_to_moist_aerosol be acceptable?
"moist" is not "ambient"; "dry" could be a special case of "moist" (RH=0%).

> I know that it has been CF policy to define "clean, textbook" definitions of
> standard names, and this is certainly desirable from a model point of
> view. On the other hand, measurements oftentimes just aren't textbook
> clean. Also, we need to continue to bring models and observations closer
> together, and such a variable would be a good way of achieving this without
> too much compromise.

All correct. CF likes to be as clear as possible, but there is no point in
being prescriptive about what people want to name. That would be the tail
wagging the dog. We have to find ways to name what people want to measure
or simulate as clearly as we can.

Best wishes

Jonathan
Received on Mon May 21 2012 - 11:20:31 BST