On the Dynamics of Concentric Eyewall Genesis: Space–Time Empirical Normal Modes Diagnosis

Martinez, Yosvany; Brunet, Gilbert; Yau, M. K.; Wang, X.

doi:10.1175/2010jas3501.1

Cited by 45 publications

(71 citation statements)

References 54 publications

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“…• small, but finite-amplitude vortex Rossby waves that propagate azimuthally, radially and vertically on the mean potential vorticity gradient of the system scale vortex (Shapiro and Montgomery 1993, Guinn and Schubert 1993, Montgomery and Kallenbach 1997, Möller and Montgomery 2000, Chen and Yau 2001, Wang 2002a, b, Chen et al 2003, McWilliams et al 2003, Martinez 2008, Martinez et al 201125 • barotropic-baroclinic shear instabilities (Schubert et al 1999, Nolan and; • eyewall mesovortices (Schubert et al 1999, Montgomery et al 2002, Braun et al 2006; and • trochoidal 'wobbling' motion of the inner-core region Montgomery 2000, Nolan et al 2001). Of course, these processes are not adiabatic and inviscid as they are coupled to the boundary layer and convection (Schecter andMontgomery 2007, Nguyen et al 2011).…”

Section: Brakes On Wishementioning

confidence: 99%

Paradigms for tropical cyclone intensification

Montgomery¹,

Smith²

2014

AMOJ

193

137

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We review the four main paradigms of tropical cyclone intensification that have emerged over the past five decades, discussing the relationship between them and highlighting their strengths and weaknesses. A major focus is on a new paradigm articulated in a series of recent papers using observations and highresolution, three-dimensional, numerical model simulations. Unlike the three previous paradigms, all of which assumed axial symmetry, the new one recognises the presence of localised, buoyant, rotating deep convection that grows in the rotation-rich environment of the incipient storm, thereby greatly amplifying the local vorticity. It exhibits also a degree of randomness that has implications for the predictability of local asymmetric features of the developing vortex. While surface moisture fluxes are required for intensification, the postulated 'evaporation-wind' feedback process that forms the basis of an earlier paradigm is not. Differences between spin up in three-dimensional and axisymmetric numerical models are discussed also.In all paradigms, the tangential winds above the boundary layer are amplified by the convectively-induced inflow in the lower troposphere in conjunction with the approximate material conservation of absolute angular momentum. This process acts also to broaden the outer circulation. Azimuthally-averaged fields from high-resolution model simulations have highlighted a second mechanism for amplifying the mean tangential winds. This mechanism, which is coupled to the first via boundary-layer dynamics, involves the convergence of absolute angular momentum within the boundary layer, where this quantity is not materially conserved, but where air parcels are displaced much further radially inwards than air parcels above the boundary layer. It explains why the maximum tangential winds occur in the boundary layer and accounts for the generation of supergradient wind speeds there. The boundary layer spin-up mechanism is not unique to tropical cyclones. It appears to be a feature of other rapidly-rotating atmospheric vortices such as tornadoes, waterspouts and dust devils and is manifest as a type of axisymmetric vortex breakdown. The mechanism for spin up above the boundary layer can be captured approximately by balance dynamics, while the boundary layer spin-up mechanism cannot. The spin-up process, as well as the structure of the mature vortex, are sensitive to the boundary-layer parameterisation used in the model.

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Section: Brakes On Wishementioning

confidence: 99%

Paradigms for tropical cyclone intensification

Montgomery¹,

Smith²

2014

AMOJ

193

137

View full text Add to dashboard Cite

show abstract

“…It recognizes also the potential role of vortex Rossby waves (VRWs 2 ) and their wave-mean and wave-wave interaction as well as their coupling to the boundary layer and convection (Chen and Yau, 2001;Wang, 2002a, b;Chen et al, 2003;Martinez, 2008;Martinez et al, 2010Martinez et al, , 2011. In other words, the tropical cyclone intensification process generally comprises a turbulent system of rotating, deep moist convection and vortex Rossby waves.…”

Section: Role Of Vortical Deep Convection In Tropical Cyclonesmentioning

confidence: 99%

Asymmetric and axisymmetric dynamics of tropical cyclones

et al. 2013

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Abstract. We present the results of idealized numerical experiments to examine the difference between tropical cyclone evolution in three-dimensional (3-D) and axisymmetric (AX) model configurations. We focus on the prototype problem for intensification, which considers the evolution of an initially unsaturated AX vortex in gradient-wind balance on an f plane. Consistent with findings of previous work, the mature intensity in the 3-D model is reduced relative to that in the AX model. In contrast with previous interpretations invoking barotropic instability and related horizontal mixing processes as a mechanism detrimental to the spin-up process, the results indicate that 3-D eddy processes associated with vortical plume structures can assist the intensification process by contributing to a radial contraction of the maximum tangential velocity and to a vertical extension of tangential winds through the depth of the troposphere. These plumes contribute significantly also to the azimuthally averaged heating rate and the corresponding azimuthal-mean overturning circulation.The comparisons show that the resolved 3-D eddy momentum fluxes above the boundary layer exhibit counter-gradient characteristics during a key spin-up period, and more generally are not solely diffusive. The effects of these eddies are thus not properly represented by the subgrid-scale parameterizations in the AX configuration. The resolved eddy fluxes act to support the contraction and intensification of the maximum tangential winds. The comparisons indicate fundamental differences between convective organization in the 3-D and AX configurations for meteorologically relevant forecast timescales. While the radial and vertical gradients of the system-scale angular rotation provide a hostile environment for deep convection in the 3-D model, with a corresponding tendency to strain the convective elements in the tangential direction, deep convection in the AX model does not suffer this tendency. Also, since during the 3-D intensification process the convection has not yet organized into annular rings, the azimuthally averaged heating rate and radial gradient thereof is considerably less than that in the AX model. This lack of organization results broadly in a slower intensification rate in the 3-D model and leads ultimately to a weaker mature vortex after 12 days of model integration. While azimuthal mean heating rates in the 3-D model are weaker than those in the AX model, local heating rates in the 3-D model exceed those in the AX model and at times the vortex in the 3-D model intensifies more rapidly than AX. Analyses of the 3-D model output do not support a recent hypothesis concerning the key role of small-scale vertical mixing processes in the upper-tropospheric outflow in controlling the intensification process.In the 3-D model, surface drag plays a particularly important role in the intensification process for the prototype intensification problem on meteorologically relevant timescales by helping foster the organization of convection in azimu...

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“…Additionally, environmental conditions may also influence the TC structure, which has been suggested in a number of studies (e.g., Hill and Lackmann 2009). Further, some theoretical and modeling studies have indicated that vortex Rossby waves (VRW) are critical to SEF (e.g., Montgomery and Kallenbach 1997;Chen and Yau 2001;Wang 2002a,b;Martinez et al 2011;Menelaou et al 2012). The key point of vortex Rossby wave theory is that the vortex Rossby waves emitted from the primary eyewall and propagated along the radial direction can accelerate the mean tangential winds at a distance from the storm center through eddy momentum flux convergence.…”

Section: Introductionmentioning

confidence: 99%

The Governing Dynamics of the Secondary Eyewall Formation of Typhoon Sinlaku (2008)

Sun

Jiang

Tan

et al. 2013

Journal of the Atmospheric Sciences

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Through successful convection-permitting simulations of Typhoon Sinlaku (2008) using a high-resolution nonhydrostatic model, this study examines the role of peripheral convection in the storm's secondary eyewall formation (SEF) and its eyewall replacement cycle (ERC). The study demonstrates that before SEF the simulated storm intensifies via an expansion of the tangential winds and an increase in the boundary layer inflow, which are accompanied by peripheral convective cells outside the primary eyewall. These convective cells, which initially formed in the outer rainbands under favorable environmental conditions and move in an inward spiral, play a crucial role in the formation of the secondary eyewall. It is hypothesized that SEF and ERC ultimately arise from the convective heating released from the inward-moving rainbands, the balanced response in the transverse circulation, and the unbalanced dynamics in the atmospheric boundary layer, along with the positive feedback between these processes.

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On the Dynamics of Concentric Eyewall Genesis: Space–Time Empirical Normal Modes Diagnosis

Cited by 45 publications

References 54 publications

Paradigms for tropical cyclone intensification

Paradigms for tropical cyclone intensification

Asymmetric and axisymmetric dynamics of tropical cyclones

The Governing Dynamics of the Secondary Eyewall Formation of Typhoon Sinlaku (2008)

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