On the distribution of subsidence in the hurricane eye

Schubert, Wayne H.; Rozoff, Christopher M.; Vigh, Jonathan L.; McNoldy, Brian D.; Kossin, James P.

doi:10.1002/qj.49

Cited by 76 publications

(101 citation statements)

References 28 publications

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“…While not a central theme of this paper, it is interesting to examine the last item above in the light of a recent study by Schubert et al (2007), who showed that the narrow region of subsidence in the eye occurs when the average Rossby length in the eye is less than 0.6 times the eye radius, which they took to be the radius of maximum tangential wind speed, R max . Schubert et al (2007) defined the local Rossby length, L R , in terms of that at large radii, say L RR , which they took to be 1000 km.…”

Section: Azimuthally Averaged Aspectsmentioning

confidence: 99%

Tropical cyclone spin‐up revisited

Smith¹,

Montgomery

Sáng³

2009

Quart J Royal Meteoro Soc

289

262

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ABSTRACT:We present numerical experiments to investigate axisymmetric interpretations of tropical cyclone spin-up in a three-dimensional model. Two mechanisms are identified for the spin-up of the mean tangential circulation. The first involves the convergence of absolute angular momentum above the boundary layer and is a mechanism to spin up the outer circulation, i.e. to increase the vortex size. The second involves the convergence of absolute angular momentum within the boundary layer and is a mechanism to spin up the inner core. It is associated with the development of supergradient wind speeds in the boundary layer. The existence of these two mechanisms provides a plausible physical explanation for certain long-standing observations of typhoons by Weatherford and Gray, which indicate that inner-core changes in the azimuthal-mean tangential wind speed often occur independently from those in the outer core. The unbalanced dynamics in the inner-core region are important in determining the maximum radial and tangential flow speeds that can be attained, and therefore important in determining the azimuthal-mean intensity of the vortex. We illustrate the importance of unbalanced flow in the boundary layer with a simple thought experiment. The analyses and interpretations presented are novel and support a recent hypothesis of the boundary layer in the inner-core region.

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Section: Azimuthally Averaged Aspectsmentioning

confidence: 99%

Tropical cyclone spin‐up revisited

Smith¹,

Montgomery

Sáng³

2009

Quart J Royal Meteoro Soc

289

262

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“…There are several derivations of the Sawyer-Eliassen equation in the literature (e.g., Shapiro and Willoughby 1982;Schubert et al 2007). In this study we integrate the version derived by Bui et al (2009):…”

Section: B the Sawyer-eliassen Modelmentioning

confidence: 99%

“…These include two-dimensional vortex interactions (Kuo et al 2004(Kuo et al , 2008, anisotropic upscale energy cascades (Terwey and Montgomery 2008), and changes in axisymmetric efficiency [as defined by Schubert and Hack (1982) and Hack and Schubert (1986)] related to the radial expansion of the azimuthally averaged tangential wind field and sustained latent heating outside of the primary eyewall ). Other models propose wave-mean flow interaction associated primarily with vortex Rossby waves and their modification to the storm inner-core region (Montgomery and Kallenbach 1997;Martinez et al 2010a,b;Menelaou et al 2012;Qiu et al 2010;Abarca and Corbosiero 2011) or the generation and accumulation of convectively induced potential vorticity anomalies and the absence of vortex Rossby wave activity (Judt and Chen 2010).…”

Section: Introductionmentioning

confidence: 99%

Departures from Axisymmetric Balance Dynamics during Secondary Eyewall Formation

Abarca

Montgomery

2014

Journal of the Atmospheric Sciences

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Departures from axisymmetric balance dynamics are quantified during a case of secondary eyewall formation. The case occurred in a three-dimensional mesoscale convection-permitting numerical simulation of a tropical cyclone, integrated from an initial weak mesoscale vortex in an idealized quiescent environment. The simulation exhibits a canonical eyewall replacement cycle. Departures from balance dynamics are quantified by comparing the azimuthally averaged secondary circulation and corresponding tangential wind tendencies of the mesoscale integration with those diagnosed as the axisymmetric balanced response of a vortex subject to diabatic and tangential momentum forcing. Balance dynamics is defined here, following the tropical cyclone literature, as those processes that maintain a vortex in axisymmetric thermal wind balance.The dynamical and thermodynamical fields needed to characterize the background vortex for the SawyerEliassen inversion are obtained by azimuthally averaging the relevant quantities in the mesoscale integration and by computing their corresponding balanced fields. Substantial differences between azimuthal averages and their homologous balance-derived fields are found in the boundary layer. These differences illustrate the inappropriateness of the balance assumption in this region of the vortex (where the secondary eyewall tangential wind maximum emerges). Although the balance model does broadly capture the sense of the forced transverse (overturning) circulation, the balance model is shown to significantly underestimate the inflow in the boundary layer. This difference translates to unexpected qualitative differences in the tangential wind tendency. The main finding is that balance dynamics does not capture the tangential wind spinup during the simulated secondary eyewall formation event.

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“…The eye is a region of subsidence and the circulation in it is 'indirect' i.e. warm air is sinking (Smith 1980, Shapiro and Willoughby 1982, Schubert et al 2007). …”

Section: Introductionmentioning

confidence: 99%

Paradigms for tropical cyclone intensification

Montgomery¹,

Smith²

2014

AMOJ

189

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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On the distribution of subsidence in the hurricane eye

Cited by 76 publications

References 28 publications

Tropical cyclone spin‐up revisited

Tropical cyclone spin‐up revisited

Departures from Axisymmetric Balance Dynamics during Secondary Eyewall Formation

Paradigms for tropical cyclone intensification

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