8.7
Dynamics of a two layer channel quasigeostrophic atmospheric model
Sergey V. Kravtsov, Univ. of California, Los Angeles, CA; and A. W. Robertson and M. Ghil
We study the dynamics of a two-layer channel baroclinic eddy-resolving quasigeostrophic atmospheric model via a variety of statistical and analytical methods.
We start by performing a long direct numerical simulation and doing an extensive EOF analysis of relevant model fields (barotropic and baroclinic streamfunctions and relative vorticities, kinetic energies and enstrophies) on raw and band pass - filtered data. Looking separately at behavior of baroclinic and barotropic modes of the system is a key feature of our analyses, which allows us to interpret the results of the EOF decompositions in a dynamical context. The low frequency barotropic dynamics is characterized by a number of weather regimes, defined as PDF maxima in the phase space of the EOFs. The weather regimes are shown to be damped solutions of the barotropic potential vorticity equation, that are energized by the stochastic forcing associated with synoptic eddies. The low frequency modifications of the synoptic storm tracks are found to be secondary phenomena, whose feedback on the barotropic low frequency modes is weak.
The study is complemented by deriving low-dimensional counterparts of the complete system and analyses of their dynamics and energetics.
Session 8, Low Frequency Variability (Continued)
Wednesday, 6 June 2001, 5:05 PM-6:00 PM
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