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contributor authorNathan, Terrence R.
date accessioned2017-06-09T14:28:09Z
date available2017-06-09T14:28:09Z
date copyright1988/03/01
date issued1988
identifier issn0022-4928
identifier otherams-19784.pdf
identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4155938
description abstractWeakly nonlinear interactions between an unstable baroclinic wave and resonant topographic wave are investigated using asymptotic methods in a two-layer, quasi-geostrophic channel model on a midlatitude beta plane in the presence of sinusoidal topography and dissipation. The asymptotic analysis pivots about slightly supercritical, vertically sheared zonal flows for which the baroclinic wave is weakly unstable and the topographic wave nearly resonant. Two long time scales are required to describe the evolution of the baroclinic wave and zonal flow connections, while the topographic wave evolves only on the longest time scale. To facilitate the numerical analysis, the method of reconstitution is used to form amplitude and zonal flow equations on a combined time scale. Examination of the analytically derived amplitude evolution equations shows that the phase of the topographic wave relative to the mountain explicitly affects the nonlinear evolution of the baroclinic wave. In contrast, phase changes in the baroclinic wave have no direct effect on the evolution of the topographic wave. Numerical integrations of the reconstituted evolution equations reveal two distinct asymptotic states of the system: 1) a single (stationary) topographic wave state where the wave trough is upstream of the mountain ridge, or 2) a mixed wave state where the baroclinic wave propagates with fixed amplitude, while the topographic wave remains stationary with its trough upstream of the mountain ridge. Single wave states, or mixed wave states dominated by the topographic wave, are, relatively speaking, favored for large zonal scales, large topographic heights, small beta and weak dissipation. However, for sufficiently small zonal scales only mixed wave states exist which are dominated by the baroclinic wave.
publisherAmerican Meteorological Society
titleFinite Amplitude Interactions between Unstable Baroclinic Waves and Resonant Topographic Waves
typeJournal Paper
journal volume45
journal issue6
journal titleJournal of the Atmospheric Sciences
identifier doi10.1175/1520-0469(1988)045<1052:FAIBUB>2.0.CO;2
journal fristpage1052
journal lastpage1071
treeJournal of the Atmospheric Sciences:;1988:;Volume( 045 ):;issue: 006
contenttypeFulltext


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