Conditional symmetric instability: Difference between revisions

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Revision as of 12:02, 6 December 2019

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===Inertial Stability===

[[File:Tourbillon total faible.png|thumb|Dark zones are regions of weak inertial stability in atmopsheric circulation.]]

In the same way, a lateral displacement of an air particle changes its absolute vortexvorticity η<math>\eta</math>. TheThis latteris given by the consistssum of the planetary vorticity, <math>f</math>, the [[Coriolis parameter]], and <math>\zeta</math>, the [[Geostrophic wind|geostrophic vortex]] (or relative) vorticity of the parcel:<ref name="Doswell"/><ref name="MF-2">{{cite web|language=French | url= http://www.meteofrance.fr/publications/glossaire?articleId=152385 | title= Instabilité barocline | publisher= [[Météo-France]] | accessdate= August 23, 2019 | work= Glossaire météorologique }}</ref>

<center><math>\eta= \left[ \frac{\partial v_rv}{\partial x} - \frac{\partial u_ru}{\partial y} \right ] + f = \zeta + f \qquad \qquad </math></center>

Where :

* <math>v</math> and <math>u</math> are the meridional and zonal geostrophic velocities respectively.

* Vg is the component of the [[geostrophic wind]] in the motion direction

*<math>x</math> and <math>y</math> correspond to the zonal and meridional coordinates.

* x is the displacement in this direction.

* ''<math>f</math>'' is the [[Coriolis parameter]], which describes the component of vorticity around the local vertical that results from the rotation of the reference frame.

* ''<math>f</math>'' increases towards the poles and decreases towards the equator

* ''<math>\zeta</math>'' variesis accordingthe torelative vorticity around the pressurelocal gradient:vertical. positiveIt foris afound rotationby anti-clockwisetaking andthe negativevertical forcomponent aof the curl of the clockwisegeostrophic rotationvelocity.

<math>\eta</math> can be positive, null or negative depending on the conditions in which the move is made. As the absolute vortex is almost always positive on the [[synoptic scale]], one can consider that the atmosphere is generally stable for lateral movement. Inertial stability is low only when <math>\eta</math> is close to zero. Since <math>f</math> is always positive, <math>\eta \le 0 </math> can be satisfied only on the anticyclonic side of a strong maximum of [[jet stream]] or in a [[Ridge (meteorology)|barometric ridge]] at altitude, where the derivative velocities in the direction of displacement in the equation give a significant negative value.<ref name="Moore" />