On the formation and maintenance of the stratospheric surf zone as inferred from the zonally averaged potential vorticity distribution

Scott, R. K.; Liu, Y. S.

doi:10.1002/qj.2377

Cited by 5 publications

(7 citation statements)

References 31 publications

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“…The consistency we have found between the planetary wave responses to applied torques and ray theory is in accordance with previous studies that have shown that ray theory appears to be successful at explaining the tropospheric response to lower stratospheric heating (Simpson et al 2009) and the extratropical stratospheric response to QBO forcing (Garfinkel et al 2012). This provides evidence that ray theory is generally useful for understanding the responses to applied forcings in the stratosphere (though this does not preclude other frameworks from also being useful, such as the non-linear approach of O'Neill and Pope (1988), or the PV-based approaches of Cohen et al (2014) and Scott and Liu (2014)).…”

Section: Fig 18mentioning

confidence: 93%

The stratospheric wintertime response to applied extratropical torques and its relationship with the annular mode

Watson

Gray

2014

Clim Dyn

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and the long-term response is less NAM-like and no longer easterly at high latitudes. This is consistent with ray theory and differences in climatological u between the two types of simulations. The response to a tropospheric wave forcing perturbation is also NAM-like. These results suggest that dynamical feedbacks tend to make the long-term NH extratropical stratospheric response to arbitrary external forcings NAM-like, but only if the feedbacks are sufficiently strong. This may explain why the observed polar vortex responses to natural forcings such as the QBO and ENSO are NAMlike. The results imply that wave feedbacks must be understood and accurately modelled in order to understand and predict the influence of GWD and other external forcings on the polar vortex, and that biases in a model's climatology will cause biases in these feedbacks.

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Section: Fig 18mentioning

confidence: 93%

The stratospheric wintertime response to applied extratropical torques and its relationship with the annular mode

Watson

Gray

2014

Clim Dyn

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“…To make clear the area-preserving nature of the perturbations, we have used ( c ) 2 ∝ 2 as the horizontal coordinate, the cylindrical equivalent of the coordinate = sin typically used in spherical geometry. While clearly a gross oversimplification, the profiles nevertheless capture the basic stratospheric wave guides of the vortex edge and subtropical flank of the surf zone (Juckes and McIntyre, 1987;Polvani et al, 1995;Scott and Liu, 2015).…”

Section: Model Descriptionmentioning

confidence: 93%

“…While clearly a gross oversimplification, the profiles nevertheless capture the basic stratospheric wave guides of the vortex edge and subtropical flank of the surf zone (Juckes and McIntyre, ; Polvani et al . ; Scott and Liu, ).…”

Section: Model Descriptionmentioning

confidence: 99%

Nonlinear latitudinal transfer of wave activity in the winter stratosphere

Scott

2019

Quart J Royal Meteoro Soc

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The transfer of wave activity between wave guides separated in latitude by a surf zone region of zero potential vorticity gradient is investigated in a simple model of the winter stratosphere and its extension into the Tropics. The distinction from classical wave propagation on a slowly varying background state is illustrated in a conceptual model in which latitudinal separation is reduced locally by wave disturbances of finite amplitude, implying a nonlinear dependence of the transfer on wave amplitude and a nonlinear transfer of wave activity to higher zonal wavenumbers. The response of a topographically forced vortex in the presence of different forms of tropical circulation, comprising either uniform or vertically localized anomalies, is examined numerically, using an exact pseudomomentum‐based wave activity to diagnose separately the vortex and tropical wave responses. Changes to the zonal mean flow in the Tropics are related in a natural way to the potential vorticity structure of the background state and the associated wave guides, which also control the general character of tracer mixing across and out of the Tropics.

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“…For q 0 thus defined, h e is obtained from Eq. assuming axisymmetry, vanishing δ and no topography, by the iterative method described in Scott and Liu (). The potential vorticity and the associated zonal wind and height profiles are as shown in Figure (a).…”

Section: Model and Experimental Designmentioning

confidence: 99%

A new class of vacillations of the stratospheric polar vortex

Scott

2016

Quart J Royal Meteoro Soc

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A new class of persistent vacillations of the winter polar vortex, under the action of topographic wave forcing and radiative cooling, is identified in numerical integrations of the rotating shallow-water equations. The vacillations are obtained provided only that care is taken to prevent the unconstrained growth of tropical easterlies that otherwise develop as the result of persistent angular momentum deposition at low latitudes. The vacillation cycle involves purely barotropic dynamics and is characterized by a dynamically controlled rapid splitting and rapid reformation of the vortex, followed by a more gradual period of vortex intensification under the influence of radiative relaxation. The onset of the splitting occurs when the frequency of the free mode of the vortex approaches that of the forcing and resembles a resonant excitation. Experiments with an alternative basic state suggest that the vacillations are a robust feature of the topographically forced and radiatively relaxed vortex. In contrast to the behaviour found in models with vertical structure, the period of the vacillation cycles here increases with increasing forcing amplitude. A wide range of forcing amplitudes exists over which the vortex exhibits distinct regime transitions between a strong, vacillating state and a state in which the vortex is weak and the zonal mean polar flow nearly zero. Comparison with observational reanalysis suggests that the vacillation cycles obtained here may be relevant to the dynamics of some sudden warming events and that the onset of a radiatively dominated regime may usefully be linked to the loss of vortex area following such an event.

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On the formation and maintenance of the stratospheric surf zone as inferred from the zonally averaged potential vorticity distribution

Cited by 5 publications

References 31 publications

The stratospheric wintertime response to applied extratropical torques and its relationship with the annular mode

The stratospheric wintertime response to applied extratropical torques and its relationship with the annular mode

Nonlinear latitudinal transfer of wave activity in the winter stratosphere

A new class of vacillations of the stratospheric polar vortex

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