Hello Jonathan,
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?). So, the proposed name would be:
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. Air temperature is the bulk
temperature of the air, not the surface (skin) temperature. The term
"surface" means the lower boundary of the atmosphere.
Option 2) This quantity, often referred to as simply the total totals
index, is defined as the difference in air temperature between two
specific air pressure levels in the troposphere summed with the
difference between the dew point temperature at the lower pressure and
the air temperature at the higher pressure. It indicates the likelihood
of severe convection. 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 air_pressure
can be specified to indicate the specific air pressures corresponding to
the air and dew point temperatures used to calculate the index.
Canonical Units: K
Do you have a feeling on which option would be better for the definition?
-Jon
On 5/18/2013 10:06 AM, Jonathan Gregory wrote:
> r Jonathan
>
>> total_totals_index
>>
>> with the associated definition:
>>
>> The Total Totals Index (TT) indicates the likelihood of severe
>> convection. 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 Total Totals Index.
> This term is not self-explanatory and presents the same kind of difficulty as
> "lifted index" (see my last email). In this case, however, it seems impossible
> to devise a short definition. Moreover, unlike lifted index, it is not a
> quantity applicable to any level; the two levels concerned are hard-wired into
> the definition. It's a one-off ad-hoc empirical quantity.
>
> As a standard name, it would be good if we could add some context to it. For
> instance, what about
>
> atmosphere_stability_total_totals_index
>
> If I have understood the definitions online and yours above, this quantity is
> actually not a dimensionless index. Its unit is K, because it is calculated by
> adding temperature differences.
>
> Best wishes
>
> Jonathan
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Received on Mon May 20 2013 - 14:42:11 BST
