[CF-metadata] Re: units - PSU

From: Steve Emmerson <steve>
Date: Tue, 10 Oct 2006 14:42:43 -0600

Hi,

The unit "PSU" could easily be added be added to the UDUNITS package
if everyone on the list would be willing to edit the installed file
"etc/udunits.dat" and add the entry

PSU S 1

(such a wonderfully brain-damaged syntax :-)

Naturally, anyone who received a netCDF file containing such a unit
would also need to have modified their UDUNITS database file -- so this
isn't an optimal solution.

Oddly enough, I have a master's degree in physical occeanography. I
believe that PSU is a dimensionless unit (like angular degrees) because
many of the thermodynamic and equation-of-state formulas require that
the halinity (salinity) quantity be dimensionless -- in order for the
equation to make sense. Personally, I'd have made the coefficients be
dimensionful so as to cancel their respective halinity values (which I'd
make dimensionful as well) -- but those formulas were developed when
halinity was measured in grams-per-gram rather than as conductance, so
the coeficients had to be dimensionless. Tradition thus demands that
PSU be dimensionless.

Regards,
Steve Emmerson
UDUNITS Developer
Received on Tue Oct 10 2006 - 14:42:43 BST