Dear Ian,
Thanks for your replies. Please see below for my responses.
>
> > > 2)
> > >
>
ratio_of_x_derivative_of_ocean_rigid_lid_pressure_to_sea_surface_densit
> > > y
> > > N kg-1
> > >
> > >
> >
---------------------------------------------------------------------
> --
> > > ---------
> > > NB: x_derivative_of_ocean_rigid_lid_pressure is already a
> > > standard_name,
> > > and I'm proposing sea_surface_density in (1).
> > >
> > The relationship between this name and existing and proposed names
is
> > clear. The term ratio is certainly used in standard names.
> Therefore I
> > think this name sounds reasonable (but please see the following
> > comments).
> >
> > Looking at the standard name table entries for
> ocean_rigid_lid_pressure
> > and x|y_derivative_of_ocean_rigid_lid_pressure which we introduced
> for
> > the NEMO model in version 10 of the table, I see that we gave them
> > canonical_units of N m-2 and N m-3 respectively. The usual practice
> in
> > standard names is to write N m-2 as Pa which would make the second
> unit
> > Pa m-1 and I think we should change the units of all three names in
> the
> > table.
>
> This is fine by me.
OK, thank you. I will amend the units for the existing names at the
next update of the standard name table.
>
> > Please note that this does not in any way prevent you from
> > writing the quantities in a file using physically equivalent units.
> For
> > the current proposal, I think we should write the canonical units as
> m
> > s-2 which is exactly equivalent to N kg-1.
>
> Fine again - and better, I suppose, since m and s are fundamental in
SI
> and N is derived.
OK, thanks.
>
> > M s-2 is the unit of
> > acceleration and I am wondering what is the physical interpretation
> of
> > the quantity you propose - does it express an acceleration in your
> > model?
> >
>
> Yes, it appears as a trend in the velocities.
>
> With a free surface height, it actually appears as g*grad(SSH), so
> perhaps a more suitable standard_name would be
>
>
product_of_acceleration_due_to_gravity_and_x_derivative_of_sea_surface_
> height_above_geoid [m s-2]
>
> - but, apparently, acceleration_due_to_gravity (or anything like it)
is
> not a CF standard_name. So we may as well stick to what I suggested
> before.
Thank you for the explanation. Your explanation of the free surface
case is helpful in understanding this quantity and I would like to
include it in the definitions. It is true that in standard names we do
not actually have any 'accelerations' but rather we have names that
refer to 'tendency of velocity'. Thus 'acceleration due to gravity'
would be expressed as
'tendency_of_downward_sea_water_velocity_due_to_gravity' (which is not a
current standard name). I don't think this approach would be
particularly helpful in producing shorter or more understandable names
for your quantities, so I am happy to go with your original proposals.
ratio_of_x_derivative_of_ocean_rigid_lid_pressure_to_sea_surface_density
and
ratio_of_y_derivative_of_ocean_rigid_lid_pressure_to_sea_surface_density
are accepted.
In summary, the three new names of
sea_surface_density; kg m-3
ratio_of_x_derivative_of_ocean_rigid_lid_pressure_to_sea_surface_density
; m s-2
ratio_of_y_derivative_of_ocean_rigid_lid_pressure_to_sea_surface_density
; m s-2
will be added to the standard name table on 10 March. On the same day
the units of the following existing names will be amended:
ocean_rigid_lid_pressure - N m-2 will change to Pa
x_derivative_of_ocean_rigid_lid_pressure - N m-3 will change to Pa m-1
y_derivative_of_ocean_rigid_lid_pressure - N m-3 will change to Pa m-1.
Best wishes,
Alison
> --
> Ian Culverwell B-2-81 Ocean and Sea Ice Modelling
> Met Office FitzRoy Road Exeter Devon EX1 3PB United Kingdom
> Tel: +44 (0)1392 884017 Fax: +44 (0)1392 885861
> E-mail: ian.culverwell at metoffice.gov.uk http://www.metoffice.gov.uk
>
> Met Office climate change predictions can now be viewed on Google
Earth
> http://www.metoffice.gov.uk/research/hadleycentre/google/
------
Alison Pamment Tel: +44 1235 778065
NCAS/British Atmospheric Data Centre Fax: +44 1235 446314
Rutherford Appleton Laboratory Email: alison.pamment at stfc.ac.uk
Chilton, Didcot, OX11 0QX, U.K.
--
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Received on Tue Feb 17 2009 - 02:47:58 GMT
