[CF-metadata] potential temperature

From: Jonathan Gregory <j.m.gregory>
Date: Fri, 3 Dec 2010 21:19:26 +0000

Dear Karl

I would suggest that we change the definition of potential temperature so that
it says *by default* the reference pressure is 1e5 Pa, but that the data var
could also have a size-one coordinate variable or a scalar coordinate variable
with the standard_name of reference_pressure_for_potential_temperature, which
I am proposing as an addition to the standard_name table, that would specify
the reference pressure. This would be backward-compatible because any existing
use of sea_water_potential_temperature would be with the default reference
pressure by definition. I agree that the definition should have said 1e5 Pa,
not sea level pressure, but I am sure that people will have used it as 1e5 Pa
and not worried about the difference. If anyone had noticed the definition and
been concerned, they would have queried it before.

The same issue arises for potential density. Is it OK to use a
reference_pressure_for_potential_temperature
to define potential density? I think so. It is the temperature which changes;
the potential density is computed from the potential temperature.

Cheers

Jonathan
Received on Fri Dec 03 2010 - 14:19:26 GMT