[CF-metadata] new standard name request for pH

From: Jonathan Gregory <j.m.gregory>
Date: Thu, 30 Apr 2009 17:22:28 +0100

Dear John

> - The vague term violates the concept of consistent units, doesn't it

I don't think so. pH is dimensionless. However, because it is dimensionless,
the exact definition has to state the unit of mass or volume being used, to
get the right numbers.

Boussinesq models (most ocean climate models are Boussinesq) treat density
as constant 1000 kg m-3 except in the computation of pressure gradients, where
it matters to the dynamics. Therefore in dealing with concentrations of
tracers, per kg and per litre are identical and to choose one or the other
would be arbitrary and hence unhelpful for data exchange.

> - The interest in making things clear to the chemist seems to be at
> the cost of making things straightforward to the people who work with
> sea water pH.

This is an issue similar to many we have had before. CF stdnames are intended
to be interdisciplinary. The use of a longer, explicit term in standard names
does not imply that there is anything wrong with the usual terminology. It
is simply intended to make things clearer to non-experts. I believe this
approach is a strength of CF standard names. What is confusing, perhaps, is
that we call them "names", which might suggest we should stick to the most
familiar terms. We use familiar terms whenever we can, but often with added
precision.

Best wishes

Jonathan
Received on Thu Apr 30 2009 - 10:22:28 BST