[FRIAM] Potential Vorticity and the Dynamic Tropopause

[Stephen Guerin]

Portrait of a Weather Watcher





On Sat, Apr 13, 2024, 12:05 PM Stephen Guerin <stephen.guerin at simtable.com>
wrote:

>
> Dan GuPTa had this response when asked to relate your .PDF to Bernard
> cells and other prompting:
>
> Here’s a integration of potential vorticity (PV), atmospheric stability,
> and their relationship to Bénard cells, emphasizing isentropic layering in
> both meteorological and experimental fluid dynamics contexts.
>
> ### Connecting Bénard Cells and Atmospheric Dynamics
>
> In Bénard cells, fluid heated from below shows a critical transition from
> conductive to convective heat transfer, forming cellular patterns.
> Similarly, in the atmosphere, when the vertical temperature gradient
> becomes unstable—akin to the Bénard cell transition—convection can
> initiate, influenced by factors like the earth's rotation and potential
> vorticity.
>
> ### Potential Vorticity and Stability
>
> - **PV on Isentropic Surfaces:** Potential vorticity combines fluid
> rotation and atmospheric stratification. In meteorology, PV is mapped on
> isentropic surfaces (constant potential temperature layers), where it
> highlights regions prone to atmospheric instability and potential
> convection, akin to early instability in Bénard cells.
>
> - **Dynamic Tropopause:** Acting like the fluid surface in a Bénard cell,
> the dynamic tropopause is flexible, responding to distortions from jet
> streams. These distortions can lead to convective activity by modifying
> local stability and vorticity, driving weather patterns similarly to
> temperature gradients in Bénard convection.
>
> ### PV Anomalies and Convective Cells
>
> - **Weather Forecasting:** Monitoring PV anomalies helps predict
> convective weather events, similar to observing Bénard cells to anticipate
> pattern formation. For example, sharp PV changes can indicate regions ripe
> for convective storms if conditions like moisture and surface temperature
> align.
>
> - **Role of Isentropic Layering:** Both in Bénard cells and weather
> systems, the spacing between isentropic layers indicates stability. Closer
> layers suggest a steep gradient and instability, potentially leading to
> convective movements. In the atmosphere, this translates to dynamic
> interactions where lower stability near the surface can trigger or enhance
> convective processes.
>
> ### Conclusion
>
> Understanding the parallels between Bénard cell dynamics and atmospheric
> conditions through potential vorticity and isentropic surfaces not only
> illustrates universal fluid dynamics principles but also enhances
> meteorological predictions of convective weather events, demonstrating how
> small-scale changes in stability can lead to significant atmospheric
> phenomena.
>
> On Thu, Apr 11, 2024, 2:04 PM Nicholas Thompson <thompnickson2 at gmail.com>
> wrote:
>
>>
>>
>> Hi, Phellow Phriammers,  Nick, here.
>>
>>
>>
>>
>>
>>
>> I have been lost in the weather.  This publication,
>>
>>
>>
>> https://acrobat.adobe.com/id/urn:aaid:sc:us:d481610b-e5d5-4a03-879c-6db6ec1d5e4a
>>
>>
>> with its glorious eye-candy, is an example of what seems to be a new
>> perspective in meteorology, the DT-PV perspective.  PV refers to a
>> parameter, potential vorticity, which seems to be a measure of how liable
>> the atmosphere is to churn; DT refers to the DYNAMIC tropopause.  The
>> tropopause is the transition zone between the stratosphere and our own
>> layer, the troposphere, through which gas exchange is limited because the
>> lapse rate of the troposphere  -- its decline in temperature with fall
>> of pressure -- is reversed in the stratosphere.   In the Bad Old Days,
>> we were taught that the tropopause was like a ceiling, tilted upward from
>> the poles to the tropics.  Now we have begun to think of it as more like
>> a tent fly, still tilted up equator-ward, but loose and floppy and buffeted
>> up and down by the jetstreams’ winds. These floppings up and down have the
>> power to destabilize the lower atmosphere and lead to bad weather, if
>> conditions there are ripe.
>>
>>
>>
>> This is not one of my usual cries for help.  I have some good tutors.
>> However, I would love to hear from others whom this paper interests.  In
>> particular I am struggling with the notion of potential vorticity, whose
>> formula seems to take many odd forms.
>>
>>
>>
>> Best,
>>
>>
>>
>> Nick
>>
>>
>>
>>
>>
>> Nicholas S. Thompson
>>
>> Emeritus Professor of Psychology and Ethology
>>
>> Clark University,
>>
>> nthompson at clarku.edu
>>
>>
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> ___________________________________________
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