Dear all,
Thanks for everyone's inputs on the atmosphere stability indices. I have
one important comment re: the lifted index. This product will
definitely need both the starting and ending pressures of the lifted
parcel in order to properly define the product. This is because the
starting and ending pressures are not fixed to certain values (unlike
some other ad-hoc indices that I have proposed, e.g. total totals index)
and can, in principle, have any values. I know that there have been a
lot of ideas for what to chose as the coordinate variable standard
names. I'm going to go with Jonathan Gregory's latest suggestion -
original_air_pressure - and expand on this to create one for
final_air_pressure. So, my current proposal for the two lifted index
products are:
Standard Name:
temperature_difference_between_ambient_air_and_air_lifted_adiabatically_from_the_surface
Definition:This quantity is defined as the temperature difference
between a parcel of air lifted adiabatically from the surface to a
finishing air pressure in the troposphere and the ambient air
temperature at the finishing air pressure in the troposphere. It is
often called the lifted index (LI) and provides a measure of the
instability of the atmosphere. The air parcel is "lifted" by moving the
air parcel from the surface to the Lifting Condensation Level (dry
adiabatically) and then from the Lifting Condensation Level to the
finishing air pressure (wet adiabatically). Air temperature is the bulk
temperature of the air, not the surface (skin) temperature. The term
"surface" means the lower boundary of the atmosphere. A coordinate
variable of final_air_pressure_of_lifted_parcel should be specified to
indicate the specific air pressure that the temperature difference is
calculated at.
Canonical Units: K
Standard Name:
temperature_difference_between_ambient_air_and_air_lifted_adiabatically
Definition:This quantity is defined as the temperature difference
between a parcel of air lifted adiabatically from a starting air
pressure to a finishing air pressure in the troposphere and the ambient
air temperature at the finishing air pressure in the troposphere. It is
often called the lifted index (LI) and provides a measure of the
instability of the atmosphere. The air parcel is "lifted" by moving the
air parcel from the starting air pressure to the Lifting Condensation
Level (dry adiabatically) and then from the Lifting Condensation Level
to the finishing air pressure (wet adiabatically). Air temperature is
the bulk temperature of the air. Coordinate variables of
original_air_pressure_of_lifted_parcel and
final_air_pressure_of_lifted_parcel should be specified to indicate the
specific air pressures at which the parcel lifting starts (original air
pressure) and the temperature difference is calculated at (final air
pressure), respectively.
Canonical Units:K
Associated coordinate variables:
Standard_names:
original_air_pressure_of_lifted_parcel
final_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).
original_air_pressure_of_lifted_parcel and final_air_pressure_of_lifted_parcel are the
pressure heights at the start and end of lifting, respectively.
Canonical units: Pa
Do these names/definitions seem satisfactory to the CF board? Sincerely,
Jonathan
On 6/5/2013 3:52 AM, Jonathan Gregory wrote:
Dear Jonathan W, Seth
I think
air_pressure_of_lifted_parcel_at_source
is fine. Seth wondered if _at_start_of_lifting would make it even clearer.
I'm inclined to think that isn't necessary ... but it made me think of yet
another possibility for your consideration, namely
original_air_pressure_of_lifted_parcel
What do you think? That avoids the confusion of "origin", I think, while
still using that word, which I think Seth suggested (originally).
ambient_air_pressure_of_lifted_parcel
is no longer needed, Seth indicates.
Cheers
Jonathan
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