Lagrangian mixing in an axisymmetric hurricane model

Rutherford, Blake; Dangelmayr, Gerhard; Persing, John; Kirby, Michael; Montgomery, Michael T.

doi:10.5194/acp-10-6777-2010

Cited by 13 publications

(3 citation statements)

References 33 publications

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“…Applications to atmospheric flows include Pierrehumbert (1991); Pierrehumbert and Yang (1993); Ngan and Sheperd (1999);von Hardenberg (2000); Joseph and Legras (2002); Scott et al (2003); Cohen and Schultz (2005); d 'Ovidio (2009); Tang et al (2010). In Sapsis and Haller (2009), Rutherford et al (2010b), andRutherford et al (2010a), FTLE's have been applied to tropical cyclones. Though FTLE's easily locate LCSs in time-dependent flows, they do not differentiate between hyperbolicity and shear effectively, and therefore would appear to have limited usefulness in flows with strong shear (d 'Ovidio, 2009), such as the inner core region of an intensifying tropical cyclone.…”

Section: Lcs Definitionmentioning

confidence: 99%

Lagrangian coherent structures in tropical cyclone intensification

Rutherford¹,

Dangelmayr²,

Montgomery³

2011

Preprint

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Recent work has suggested that tropical cyclones intensify via a pathway of rotating deep moist convection in the presence of enhanced fluxes of moisture from the ocean. The rotating deep convective structures possessing enhanced cyclonic vorticity within their cores have been dubbed Vortical Hot Towers (VHTs). In general, the interaction between VHTs and the system-scale vortex, as well as the corresponding evolution of equivalent potential temperature θe that modulates the VHT activity, is a complex problem in moist helical turbulence. To better understand the structural aspects of the three-dimensional intensification process, a Lagrangian perspective is explored that focuses on the localized stirring around VHTs and their vortical remnants, as well as the evolution and stirring of θe. Recently developed finite-time Lagrangian methods are limited in the three-dimensional turbulence and shear associated with the VHTs. In this paper, new Lagrangian techniques developed for three-dimensional velocity fields are summarized and we apply these techniques to study VHT and θe phenomenology. Our primary findings are that VHTs are coherent Lagrangian vortices that create a turbulent mixing environment. Associated with the VHTs are hyperbolic structures that modulate the aggregation of VHTs and their vortical remnants. Although the azimuthally-averaged inflow is responsible for the inward advection of boundary layer θe, the Lagrangian coherent structures are found to modulate the convection emanating from the boundary layer by stirring θe along organized attracting boundaries. Extensions of boundary layer coherent structures grow above the boundary layer during episodes of convection are responsible for organizing the remnants of the convective vortices. These hyperbolic structures form initially as boundaries between VHTs, but persist above the boundary layer and outlive the VHTs to eventually form the primary eyewall as the vortex attains maturity

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Section: Lcs Definitionmentioning

confidence: 99%

Lagrangian coherent structures in tropical cyclone intensification

Rutherford¹,

Dangelmayr²,

Montgomery³

2011

Preprint

Self Cite

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“…FTLE and similar versions of the Lyapunov exponent have been used to estimate LCSs in different models of at-mospheric flows, such as a zonal stratospheric jet (Beron-Vera et al, 2010), a jet-stream (Tang et al, 2010), a hurricane (Rutherford et al, 2010), transient baroclinic eddies (von Hardenberg and Lunkeit, 2002) and the polar vortex (Koh and Legras, 2002).…”

Section: Introductionmentioning

confidence: 99%

Atmospheric rivers as Lagrangian coherent structures

Garaboa,

Eiras-Barca,

Huhn

et al. 2015

Preprint

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We show that filamentous Atmospheric Rivers (ARs) over the Northern Atlantic Ocean are closely linked to attracting Lagrangian Coherent Structures (LCSs) in the large scale wind field. LCSs represent lines of attraction in the evolving flow with a significant impact on all passive tracers. Using Finite-Time Lyapunov Exponents (FTLE), we extract LCSs from a two-dimensional flow derived from water vapor flux of atmospheric reanalysis data and compare them to the three-dimensional LCS obtained from the wind flow. We correlate the typical filamentous water vapor patterns of ARs with LCSs and find that LCSs bound the filaments on the back side. Passive advective transport of water vapor from tropical latitudes is potentially possible.

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“…Rutherford et al: Advective mixing in a nondivergent barotropic hurricane model eye-eyewall mixing occurs during polygonal eyewall transitions. Lagrangian mixing in the axisymmetric model introduced in Rotunno and Emanuel (1987) is investigated in Rutherford et al (2009). For another discussion of axisymmetric mixing, see Wirth and Dunkerton (2006).…”

Section: Introductionmentioning

confidence: 99%

Advective mixing in a nondivergent barotropic hurricane model

Rutherford¹,

Dangelmayr²,

Persing³

et al. 2009

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Abstract. This paper studies Lagrangian mixing in a two-dimensional barotropic model for hurricane-like vortices. Since such flows show high shearing in the radial direction, particle separation across shear-lines is diagnosed through a Lagrangian field, referred to as R-field, that measures trajectory separation orthogonal to the Lagrangian velocity. The shear-lines are identified with the level-contours of another Lagrangian field, referred to as S-field, that measures the average shear-strength along a trajectory. Other fields used for model diagnostics are the Lagrangian field of finite-time Lyapunov exponents (FTLE-field), the Eulerian Q-field, and the angular velocity field. Because of the high shearing, the FTLE-field is not a suitable indicator for advective mixing, and in particular does not exhibit clear ridges marking the location of finite-time stable and unstable manifolds. The FTLE-field is similar in structure to the radial derivative of the angular velocity. In contrast, distinct and persisting ridges and valleys can be clearly recognized in the R-field, and their propagation speed indicates that transport across shear-lines is caused by Rossby waves. A radial mixing rate derived from the R-field gives a time-dependent measure of flux across the shear-lines. On the other hand, a measured mixing rate across the shear-lines, which counts trajectory crossings, confirms the results from the R-field mixing rate, and shows high mixing in the eyewall region after the formation of a polygonal eyewall, which continues until the vortex breaks down.

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Lagrangian mixing in an axisymmetric hurricane model

Cited by 13 publications

References 33 publications

Lagrangian coherent structures in tropical cyclone intensification

Lagrangian coherent structures in tropical cyclone intensification

Atmospheric rivers as Lagrangian coherent structures

Advective mixing in a nondivergent barotropic hurricane model

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