On Radiating Instabilities and Resonant Overreflection

McIntyre, Michael E.; Weissman, Michael A.

doi:10.1175/1520-0469(1978)035<1190:oriaro>2.0.co;2

Cited by 52 publications

(41 citation statements)

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“…Thus, the shear is unstable and hence conducive for the excitation of KHI, leading to the generation of the propagating GWs through nonlinear interaction. Note that shear excitation of the GWs has been examined theoretically using both linear and nonlinear approaches (e.g., Fritts, 1982Fritts, , 1984McIntyre, 1978). For the excitation of radiating GWs by KHIs at a shear layer, the two mechanisms that are examined are the vortex pairing (sub-harmonic interaction) and envelope radiation (Fritts, 1984).…”

Section: Discussion On the Potential Source(s) Of The Gw Eventsmentioning

confidence: 99%

Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

et al. 2015

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Abstract. Sources and propagation characteristics of highfrequency gravity waves observed in the mesosphere using airglow emissions from Gadanki (13.5 • N, 79.2 • E) and Hyderabad (17.5 • N, 78.5 • E) are investigated using reverse ray tracing. Wave amplitudes are also traced back, including both radiative and diffusive damping. The ray tracing is performed using background temperature and wind data obtained from the MSISE-90 and HWM-07 models, respectively. For the Gadanki region, the suitability of these models is tested. Further, a climatological model of the background atmosphere for the Gadanki region has been developed using nearly 30 years of observations available from a variety of groundbased (MST radar, radiosondes, MF radar) and rocket-and satellite-borne measurements. ERA-Interim products are utilized for constructing background parameters corresponding to the meteorological conditions of the observations. With the reverse ray-tracing method, the source locations for nine wave events could be identified to be in the upper troposphere, whereas for five other events the waves terminated in the mesosphere itself. Uncertainty in locating the terminal points of wave events in the horizontal direction is estimated to be within 50-100 km and 150-300 km for Gadanki and Hyderabad wave events, respectively. This uncertainty arises mainly due to non-consideration of the day-to-day variability in the tidal amplitudes. Prevailing conditions at the terminal points for each of the 14 events are provided. As no convection in and around the terminal points is noticed, convection is unlikely to be the source. Interestingly, large (∼ 9 m s −1 km −1 ) vertical shears in the horizontal wind are noticed near the ray terminal points (at 10-12 km altitude) and are thus identified to be the source for generating the observed highphase-speed, high-frequency gravity waves.

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Section: Discussion On the Potential Source(s) Of The Gw Eventsmentioning

confidence: 99%

Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

et al. 2015

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“…The third criterion is the so-called phase speed condition (McIntyre and Weissman, 1978;Talley, 1983;Malanotte-Rizzoli et al, 1987;Ierley and Young, 1991). The frequency and wavenumber of the solution of the linear eigenvalue problem must match those of the Rossby wave in the far field in order for the unstable mode to radiate.…”

Section: Unbounded Meridional Bickley Jetmentioning

confidence: 99%

Instabilities of an eastern boundary current with and without large-scale flow influence

Wang¹

2011

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Eastern oceanic boundary currents are subject to hydrodynamic instability, generate small scale features that are visible in satellite images and may radiate westward into the interior, where they can be modified by the large-scale circulations. This thesis studies the stability of an eastern boundary current with and without the large-scale flow influence in an idealized framework represented by barotropic quasi-geostrophic dynamics.The linear stability analysis of a meridional current with a continuous velocity profile shows that meridional eastern and western boundary currents support a limited number of radiating modes with long meridional and zonal wavelengths and small growth rates. However, the linearly stable, long radiating modes of an eastern boundary current can become nonlinearly unstable by resonating with short trapped unstable modes. This phenomenon is clearly demonstrated in the weakly nonlinear simulations. Results suggest that linearly stable longwave modes deserve more attention when the radiating instability of a meridional boundary current is considered.A large-scale flow affects the short trapped unstable mode and long radiating mode through different mechanisms. The large-scale flow modifies the structure of the boundary current to stabilize or destabilize the unstable modes, leading to a meridionally localized maximum in the perturbation kinetic energy field. The shortwave mode is accelerated or decelerated by the meridional velocity adjustment of the large-scale flow to have an elongated or a squeezed meridional structure, which is confirmed both in a linear WKB analysis and in nonlinear simulations. The squeezed or elongated unstable mode detunes the nonlinear resonance with the longwave modes, which then become less energetic. These two modes show different meridional structures in kinetic energy field because of the different mechanisms.In spite of the model simplicity, these results can potentially explain the formation of the zonal jets observed in altimeter data, and indicate the influence of the large-3 scale wind-driven circulation on eastern boundary upwelling systems in the real ocean. Studies with more realistic configurations remain future challenges.

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“…A current is said to be radiatingly unstable if the wavenumbers and frequencies of the perturbations generated by a local instability of the flow are such that they match those of the freely propagating Rossby waves in the ocean interior (McIntyre and Weissman, 1978). In this case, Rossby waves are excited by the local instability that carry energy away from the source (Talley, 1983a;Pierrehumbert, 1984).…”

Section: Radiating Instabilities Of Meridional Currentsmentioning

confidence: 99%

“…An instability is said to be radiating if it has the ability through the excitation of Rossby waves to extend its influence beyond its origin region. A necessary condition for radiation is that the wavelengths and frequencies of the perturbations generated by the local instability of the current match those of the freely propagating Rossby waves in the ocean interior (McIntyre and Weissman, 1978). Radiating instabilities can be seen as a mechanism leading to the redistribution of eddy energy in a system.…”

Section: Introductionmentioning

confidence: 99%

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Stability of large-scale oceanic flows and the importance of non-local effects

Hristova¹

2009

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On Radiating Instabilities and Resonant Overreflection

Cited by 52 publications

References 0 publications

Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

Instabilities of an eastern boundary current with and without large-scale flow influence

Stability of large-scale oceanic flows and the importance of non-local effects

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