Dear Seth,
Yes, I remember your new standard names. In fact, I just updated the
definition of the lifted index to include these two names. However, the
total totals index (and others, such as the showalter index) are
somewhat different beasts than the lifted index in that they really do
not have 'non-standard heights' for calculating the index. As far as I
know (and someone please correct me if I am wrong), the pressure height
levels for the total totals index are specifically fixed to 850 and 500
hPa. I am not aware of the total totals index being calculated at any
other pressure levels, so I chose not to include the air_pressure_of_X
standard names as coordinate variables in the definition since I figured
there was no obvious reason to generalize these definitions. I also
left them out of the showalter index definition, as well. These
stability indices are in effect unique, one-off, quantities that don't
really need further generalization, at least as I see it.
Related to this point, some might argue that the lifted index standard
name is also fixed to the surface and 500 hPa pressure levels. While
this is generally the case, I believe, I have found some instances where
the 500 hPa level is not used when calculating the index. So, I think
of the lifted index as more of a general index for adiabatic lifting of
a parcel between two arbitrary pressure levels, and thus should include
your two proposed air_pressure_of_X standard names.
Sincerely,
Jonathan
On 5/29/2013 2:11 PM, Seth McGinnis wrote:
Hi Jonathan,
I suggested two such standard_names in an email on Friday,
because I need them for various CAPE/CIN/etc standard_names:
air_pressure_of_lifted_parcel_at_start
air_pressure_of_lifted_parcel_at_finish
These would have the following 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_start
[finish] is the pressure height at the beginning [end] of lifting.
Both would have canonical units of Pa
We could then add the following final sentence to the definition for the
total totals index: "If the index is calculated between non-standard
heights, they should be specified using auxiliary coordinate variables of
air_pressure_of_lifted_parcel_at_start and
air_pressure_of_lifted_parcel_at_finish."
Does that seem like it would work?
Cheers,
--Seth
On Wed, 29 May 2013 18:17:49 +0100
Jonathan Gregory <j.m.greg...@reading.ac.uk> wrote:
Dear Jonathan
It would be all right to specify coordinate variables (size one or scalar)
for the two levels, but they would have to be distinguishable. That means
they'd have to have different standard names, I suppose - what would they be?
It seems to me this would then tend towards the generalisation of this
quantity, for which you didn't see an immediate need when you proposed it.
It would be simpler to remain hard-wired, if that's the use-case.
Best wishes
Jonathan
----- Forwarded message from Jonathan Wrotny <jwro...@aer.com> -----
Date: Wed, 29 May 2013 12:00:42 -0400
From: Jonathan Wrotny <jwro...@aer.com>
User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/20130509
Thunderbird/17.0.6
To: Jonathan Gregory <j.m.greg...@reading.ac.uk>, John Graybeal
<grayb...@marinemetadata.org>, cf-metadata@cgd.ucar.edu
Subject: Re: [CF-metadata] new standard name: total_totals_index
Jonathan,
I wanted to make a minor addition to the definition of the total
totals index to include coordinate variables for the 850 and 500 hPa
pressure levels. It seems that this information might be useful to
have in a netCDF file, but not be specifically required. Please let
me know if you think this sentence is unnecessary and I can remove.
Standard Name:
atmosphere_stability_total_totals_index
Definition:
The atmosphere_stability_total_totals_index indicates the
likelihood of severe convection and is often referred to as simply the
total totals index. The index is derived from the difference in air
temperature between 850 and 500 hPa (the vertical totals) and the
difference between the dew point temperature at 850 hPa and the air
temperature at 500 hPa (the cross totals). The vertical totals and cross
totals are summed to obtain the index.Coordinate variables can be specified
which
indicate the 850 and 500 hPa pressure levels.
Canonical Units: K
Does this standard name/definition/units seems suitable to the CF board?
FYI, I will be submitting two other stability indices this week. Sincerely,
Jonathan
On 5/22/2013 1:42 PM, Jonathan Wrotny wrote:
Dear Jonathan,
Thanks for your feedback. I agree with your suggested
modifications the definition and have included them below.
Also, there is an e-mail from John Graybeal who is suggesting a
more generalized version of the standard name. I have thought
about attempting to come up with a similar, general, name for the
total totals index. But, this name was so long that I believe
that it would itself become a full description, which I was trying
to avoid. John's suggested name boils it down more generally and
succintly, but it turns out that this name could also be
applicable to the stability index, "k index," which I am going to
submit in the coming days (which also uses differences of the
ambient and dew point temperatures), so there would be conflict
with the "k index" name. Also, remember that the total totals is
not a name that I have personally constructed to describe the
mathematics of the quantity, but it is actually the name of an
commonly used meteorological quantity.
Given Jonathan's previous direction (see e-mails concerning
"lifted index") to attempt to standardize all names except for
those specific, complex quantities that don't lend themselves to
generalization, I think keeping total_totals_index in the standard
name is a good idea. I think the lifted index is complex and
specific enough that it falls into the category or meriting a
unique name (similar to, say, the NDVI).
Standard Name:
atmosphere_stability_total_totals_index
Definition:
The atmosphere_stability_total_totals_index indicates the
likelihood of severe convection and is often referred to as simply the
total totals index. The index is derived from the difference in air
temperature between 850 and 500 hPa (the vertical totals) and the
difference between the dew point temperature at 850 hPa and the air
temperature at 500 hPa (the cross totals). The vertical totals and cross
totals are summed to obtain the index.
Canonical Units: K
Sincerely,
Jonathan
On 5/21/2013 5:39 PM, Jonathan Gregory wrote:
Dear Jon
I agree with your assessment, and I like your proposed name. My
only question remains with the definition. It seems like there
could be two approaches given the specific nature of the product: 1)
write the definition as below with hard-wired pressure levels part
of the definition. Based on my understanding of the product, I have
never seen any other pressures levels other than 500 and 850 hPa
used for the index, but I could be wrong. -or- 2) attempt to
generalize the definition so that it does not mention the specific
pressure levels. This would help to generalize the definition, but
may not add that much value since other pressure levels do not
appear to be commonly used (ever?).
If that is the case, then (1) seems the better choice
Standard Name: atmosphere_stability_total_totals_index
Definition:
Option 1)The atmosphere_stability_total_totals_index indicates the
likelihood of severe convection and is often referred to as simply
the total totals index. The index is derived from the difference in
air temperature between 850 and 500 hPa (the vertical totals) and
the difference between the dew point temperature at 850 hPa and the
air temperature at 500 hPa (the cross totals). The vertical totals
and cross totals are summed to obtain the index.
You could insert
often referred to as simply the total totals index
as in your other definition. This bit:
Air temperature is
the bulk temperature of the air, not the surface (skin) temperature.
The term "surface" means the lower boundary of the atmosphere.
doesn't seem necessary in this case, since "surface" is not mentioned.
Canonical Units: K
Oh, good. :-)
If we define it specifically now, that does not preclude the later
addition of
a more general standard name if required.
Cheers
Jonathan
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