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.gregory at 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 <jwrotny at aer.com> -----
>>
>>> Date: Wed, 29 May 2013 12:00:42 -0400
>>> From: Jonathan Wrotny <jwrotny at 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.gregory at reading.ac.uk>, John Graybeal
>>> <graybeal at marinemetadata.org>, cf-metadata at 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
>>>>> _______________________________________________
>>>>> CF-metadata mailing list
>>>>> CF-metadata at cgd.ucar.edu
>>>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>>>>
>>>>
>>>> _______________________________________________
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>>>> CF-metadata at cgd.ucar.edu
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>> ----- End forwarded message -----
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Received on Wed May 29 2013 - 12:31:03 BST
