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| Titel |
Strong KAM stability in the summer hemisphere subtropical stratosphere |
| VerfasserIn |
F. J. Beron-Vera, M. J. Olascoaga, M. G. Brown |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250019923
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| Zusammenfassung |
| We have recently proposed a new explanation for the confinement of ozone-depleted air
within the stratospheric polar vortex. The proposed mechanism differs from the traditional
potential vorticity (PV) barrier mechanism in that it does not make use of dynamical
constraints on the streamfunction. Rather, it is built on new results relating to the
Kolmogorov–Arnold–Moser (KAM) theory for nonautonomous one-degree-of-freedom
Hamiltonian systems with degeneracy. The new mechanism, which we have referred to as
strong KAM stability, leads to the possibility that transport barriers in PV-conserving flows
occur at locations that do not necessarily coincide with PV barriers. More specifically, it
predicts that barriers should be present near westward jet core latitudes. We have argued that
strong KAM stability provides an explanation for Jupiter’s midlatitude weather
layer belt–zone structure. Also, in addition to arguing that strong KAM stability
provides an explanation for the trapping of ozone-depleted air within the stratospheric
polar vortex, we have discussed its relevance for the Earth’s summer hemisphere
subtropical stratosphere. There westward jets develop with associated weak PV gradients.
There exists observational evidence that links these westward jets, which constitute
important elements of the so-called “tropical pipe,” with barriers for the transport of
long-lived chemical tracers. We search for evidence of this behavior in CMAM
(Canadian Middle Atmosphere Model) winds on different isentropic levels. This is
done by carrying out passive tracer evolution computations, computing finite-time
Lyapunov exponent fields, and extracting from the latter Lagrangian coherent structures. |
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