Dear All,
I think that this is a key example of where it is vital to include the
'alias' field in the standard name XML table (which is what CF allows us to
do). In reality, most people are going to be thinking of this parameter as
'omega' when looking for it but I agree that the actual standard name should
describe the physical quantity as accurately as possible.
Ag
> -----Original Message-----
> From: cf-metadata-bounces at cgd.ucar.edu
> [mailto:cf-metadata-bounces at cgd.ucar.edu]On Behalf Of Jonathan Gregory
> Sent: 09 February 2004 22:59
> To:
> Subject: [CF-metadata] omega
>
>
> Dear All
>
> Last year we replaced "omega" with the more explicit
> vertical_air_velocity_expressed_as_tendency_of_pressure
> but this is rather clumsy.
>
> It has been suggested we should instead have
> vertical_velocity_in_pressure_coordinates
> Speaking for myself, I feel that this is not so good,
> although more familiar,
> because I think the sign convention is not obvious, and I am
> worried it might
> be mistaken for vertical velocity on pressure levels.
>
> Mike Blackburn has pointed out that omega isn't strictly
> vertical velocity,
> since pressure surfaces are not necessarily horizontal. Omega
> is actually the
> rate of change of pressure of an air parcel. This suggests a
> new possibility:
> langrangian_tendency_of_air_pressure
> for omega. What do you think? I like this because it is
> accurate and shorter
> than the others. We could define lagrangian_tendency in the
> guidelines. The
> usual tendency is Eulerian. Plain tendency_of_air_pressure,
> which is already
> a standard name, means the partial derivative wrt time e.g.
> of air pressure
> measured at a synoptic station, whereas lagrangian_tendency
> means the total
> derivative i.e. following a parcel.
>
> The same argument would apply to vertical air velocity in
> sigma coordinates.
>
> Cheers
>
> Jonathan
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Received on Tue Feb 10 2004 - 01:35:04 GMT
