Jonathan W--
Whoops, two Jonathans in the thread -- I should have included a last name.
Sorry for the confusion!
My reply was to Jonathan Gregory's question about indicating the start/end
pressures.
If the total totals and showalter indices are always calculated for the same
pressure heights, I agree, it makes sense to include those in the definition
and leave off any mention of starting/ending coordinate variables.
(But now we've got a backup option in case someone comes up with a
generalized version that isn't always 500/850 mb...)
Cheers,
--Seth
On Wed, 29 May 2013 14:31:03 -0400
Jonathan Wrotny <jwrotny at aer.com> wrote:
>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
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>>>>>
>>>>>
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Received on Wed May 29 2013 - 12:40:25 BST
