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| Titel |
Energetics associated with the variabilities of the northern and southern stratospheric polar vortices |
| VerfasserIn |
José M. Castanheira, Carlos A. F. Marques |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250114084
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| Publikation (Nr.) |
 EGU/EGU2015-14378.pdf |
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| Zusammenfassung |
| The time variations in the kinetic and available potential energies, and in the interactions an
conversions between the two forms of energy will be discussed for periods of strong
accelerations or strong decelerations of the stratospheric polar vortex. The analysis was
performed separately for the northern and the southern polar vortices. The similarities and
differences between the two hemispheres may help to elucidate the relative roles of the
internal stratospheric dynamics and planetary wave forcing in the variability of the polar
vortex.
The analysis is based on a 3-dimensional (3-D) decomposition of the energy cycle of the
general atmospheric circulation by using the 3-D normal mode functions of the primitive
equations linearized about an adiabatic reference state at rest (Marques and Castanheira,
2012). The 3-D normal-mode energetics scheme allows one to partition the kinetic and
available potential energy amounts, as well as their interactions and conversions,
onto zonal mean and eddy components, and also onto barotropic and baroclinic
components.
A marked barotropic signal during strong variations of the polar vortex strengths,
associated with the extratropical annular mode variability, is clearly seen in the barotropic
components of the kinetic and available potential energies. The strong vortex decelerations
are preceded by an increase in the flow of baroclinic available potential energy from the
zonal mean to the baroclinic eddies and an increase of conversion of the baroclinic
eddy available potential energy into eddy kinetic energy, with the total (kinetic
+ available potential) energy peaking during the transition from strong to weak
vortex. During the vortex accelerations there is a decrease of conversion of the
baroclinic eddy available potential energy into eddy kinetic energy, in agreement
with a recovering of the vortex by radiative relaxation. The time variations of the
zonal mean barotropic components of the energy follows the variation of the vortex
intensity, and have relatively low frequencies. On the other the time variations of the
baroclinic components have higher frequencies showing a peak around 30 days,
that seems to be phase locked with the strong vortex accelerations or strong vortex
decelerations.
ÂÂ
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Marques CAF, Castanheira JM (2012), A detailed normal mode energetics of the general
circulation of the atmosphere. J. Atmos Sci, 69(9):2718–2732. |
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