Dear Jonathan Gregory,
Thanks for creating the new thread....
I see your point on how "start" and "finish" could imply a trajectory
and that we should avoid this. I like the word "source" instead of
"start." "Ambient" doesn't imply any height, in and of itself. But,
since it is used in the standard name and definition, hopefully it is
clear to others that it refers to the final pressure level in the
"notional journey" of the lifted parcel, like you say. I'm not sure of
the best names for the coordinate variables, but here is my crack at
them. Perhaps Seth can chime in and make any suggestions he has -
hopefully this doesn't "throw off" his proposed definitions too much.
Associated coordinate variables:
Standard_names:
air_pressure_of_lifted_parcel_at_source
ambient_air_pressure_of_lifted_parcel
Definitions:
Various stability and convective potential indices are calculated by "lifting"
a parcel of air: moving it dry adiabatically from a starting height (often the surface)
to the Lifting Condensation Level, and then wet adiabatically from there to an ending
height (often the top of the data/model/atmosphere).
air_pressure_of_lifted_parcel_at_source and ambient_air_pressure_of_lifted_parcel are the
pressure heights at the start and end of lifting, respectively.
Canonical units: Pa
The only one of the four stability indices that I have proposed which
uses these coordinate variables is the lifted index. I will wait to
send an updated definition for the lifted index once we have resolved
the coordinate variables question.
Sincerely,
Jonathan
On 6/4/2013 5:28 AM, Jonathan Gregory wrote:
Dear all
I chose a new subject because these threads about lifted_index, total_totals_
index and Seth's new standard names for CIN etc. are closely related.
I agree with the suggestion from Philip to include _from_the_surface on names
referring to surface parcels (it was previously clarified that really means
from the surface, not "surface air" i.e. screen height), and omit it when the
parcel comes from a different level that is identified by a numeric coordinate.
That is consistent with the general pattern that special physical surfaces
(such as the surface i.e. bottom of atmos) appear by name in standard_names
when relevant, whereas levels specified by coordinates do not.
Excuse my making a late suggestion on another matter. I think "start" and
"finish" are OK but they make it sound like a real trajectory, whereas these
are just calculations from the state of the atmos. I would therefore like to
suggest "source" (for "start"), which has the same sense of "where the parcel
came from" that "origin" has, but doesn't have the potential confusion. E.g.
air_pressure_of_lifted_parcel_at_source. What do you think?
As for "finish", which names require this? I wonder about using "ambient" for
"finish", in cases where the idea is to compare the parcel with the environment
at the end of its notional journey. Again, what do you think?
Going back to Seth's proposal, I wonder if
atmosphere_specific_convective_inhibition
atmosphere_specific_convective_available_potential_energy
are really best regarded as a trajectory. They are integral quantities. In
those two cases, I suggest it would be fairly natural to give them bounds in
a vertical coordinate to indicate the limits of integration.
Best wishes
Jonathan
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