| Localized and persistent jets are ubiquitous in the atmosphere and oceans. The instability of a three-dimensional localized jet over western North Pacific Ocean in winter gives rise to the so-called Pacific storm-track. The disturbances associated with such a storm track are three-dimensional propagating wave-packets. It is hypothesized that the intensification mechanism can be succinctly interpreted as resonant interactions among the constituent potential vorticity anomalies associated with a representative unstable wave packet in the presence of such a jet. Those interactions give rise to mutual influences among the PV anomalies due to their individual advection of the background potential vorticity field. Supporting evidence from a model analysis for this hypothesis will be presented. It is also instructive to distinguish barotropic resonant interactions from baroclinic resonant interactions. A complementary diagnosis of the local energetics of an unstable disturbance will be reported, further delineating how such general instability takes place. Furthermore, the maintenance of a storm track will be discussed on the basis of an analysis of the nonlinear simulation.The intensity of the Pacific storm track is also known to be distinctly weaker in mid-winter, when the jet is strongest, than in early- or late- winter. If time permits, a dynamical account for this counter-intuitive phenomenon known as ÅÎid-winter suppression¡|will be proposed. |
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