Hi Philip,
I could go for that. I wasn't sure if there were any established usages
regarding start/origin/beginning/etc or end/finish/etc, so I picked that pair
as a first stab at it just on the grounds of sounding nice to my ear.
Your argument makes sense, and I'd be happy to go that way. Further input is
also welcome.
Cheers,
--Seth
On Sat, 25 May 2013 07:25:49 +0000
"Cameron-smith, Philip" <cameronsmith1 at llnl.gov> wrote:
>Hi Seth, et al.,
>
>air_pressure_of_lifted_parcel_at_origin
>air_pressure_of_lifted_parcel_at_finish
>
>Would it make sense to replace 'origin' with 'start'? I can think of a
>couple of ways 'origin' might cause confusion: it can refer to the (0,0) point
>in a coordinate system, and a parcel involved in convection (eg over
>California) might have originated far away over Alaska. I think most people
>would quickly figure out what you mean, but since 'start' is typically paired
>with 'finish' anyway, why not use 'start'?
>
>Best wishes,
>
> Philip
>
>-----------------------------------------------------------------------
>Dr Philip Cameron-Smith, pjc at llnl.gov, Lawrence Livermore National Lab.
>-----------------------------------------------------------------------
>
>-----Original Message-----
>From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Seth
>McGinnis
>Sent: Friday, May 24, 2013 4:58 PM
>To: cf-metadata at cgd.ucar.edu
>Subject: [CF-metadata] new standard names for CIN, LFC,LCL; update to CAPE
>
>Greetings CF mailing list!
>
>I would like to propose some new standard_names related to convective
>instability indices.
>
>I apologize for sending such a long proposal right before a holiday weekend in
>the US, but I've been working on it for a while and it dovetails with the
>recent discussion of a standard_name for Lifted Index. In that discussion,
>I've proposed two new standard names to record the starting and ending points
>of a lifted parcel:
>
>air_pressure_of_lifted_parcel_at_origin
>air_pressure_of_lifted_parcel_at_finish
>
>
>Given this (or some other) way of specifying the lifted parcel, we can then
>handle variables recording various of its properties. I would like to propose
>three new standard_names for CIN, LCL, and LFC, and to add to the existing
>definition for CAPE, as follows:
>
>
>CIN:
>
>name: atmosphere_specific_convective_inhibition
>
>Convective inhibition is the amount of energy required to overcome the
>negatively buoyant energy exerted by the environment on a parcel of air.
> Convective inhibition is often abbreviated as "CIN" or "CINH".
>It is calculated by integrating the negative differences in virtual
>temperature between a parcel of air lifted adiabatically and its surroundings.
> If the start and/or end points of the lifted parcel are not specified using
>auxiliary coordinate variables with the standard_names
>air_pressure_of_lifted_parcel_at_origin (_finish), the parcel starts at the
>surface (lower boundary of the atmosphere) and ends at the top of the
>atmosphere.
>
>canonical units: J/kg
>
>
>LCL:
>
>name: atmosphere_lifted_condensation_level
>
>The lifting condensation level is the height at which the relative humidity of
>an air parcel cooled by dry adiabatic lifting would reach 100%. If the
>starting point of the lifted parcel is not specified using an auxiliary
>coordinate variable with the standard_name
>air_pressure_of_lifted_parcel_at_start, the parcel starts at the surface
>(lower boundary of the atmosphere).
>
>canonical units: m
>
>
>[Note that, wikipedia notwithstanding, Google reports "liftING condensation
>level" as more commonly used than "liftED condensation level" by about 5:4.
> Personally, I have no strong feelings about it one way or the other, and will
>gladly bow to anyone who has an opinion based on observations in the wild.]
>
>
>LFC:
>
>name: atmosphere_level_of_free_convection
>
>The level of free convection is the altitude where the temperature of the
>environment decreases faster than the moist adiabatic lapse rate of a
>saturated air parcel at the same level. It is calculated by lifting a parcel
>of air dry adiabatically to the LCL (lifted condensation level), then moist
>adiabatically until the parcel temperature is equal to the ambient
>temperature. If the starting point of the lifted parcel is not specified
>using an auxiliary coordinate variable with the standard_name
>air_pressure_of_lifted_parcel_at_start, the parcel starts at the surface
>(lower boundary of the atmosphere).
>
>canonical units: m
>
>
>CAPE:
>
>CAPE already exists in the standard name table as
>atmosphere_specific_convective_available_potential_energy
>
>There are apparently several different flavors of CAPE depending on how one
>chooses the starting point of the lifted parcel. (Among others, there's
>surface-based, most-unstable, and maximum-theta-e
>CAPE.) Rather than propose several new standard_names for the different
>flavors, I think they can be handled by simply adding an explanatory note in
>the metadata -- as long as the starting height of the parcel can be recorded.
>
>So I propose that we update the existing CAPE definition to default to being
>surface-based, and add an explanation of the whole lifted parcel business so
>that other flavors can be accommodated by noting the starting heights, as
>follows:
>
>
>Additions to definition of
>atmosphere_specific_convective_available_potential_energy:
>
>Convective(ly) available potential energy (often abbreviated CAPE) is a
>stability measure typically calculated by integrating the positive differences
>in virtual temperature between a parcel of air lifted adiabatically and its
>surroundings. If the start and/or end points of the lifted parcel are not
>specified using auxiliary coordinate variables with the standard_names
>air_pressure_of_lifted_parcel_at_origin (_finish), the parcel starts at the
>surface (lower boundary of the atmosphere) and ends at the top of the
>atmosphere. [remainder of existing definition goes here]
>
>Cheers,
>
>--Seth
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Received on Mon May 27 2013 - 22:41:14 BST
