Filamentation Time Diagnosis of Thinning Troughs and Cutoff Lows

Tsai, Yu-Ming; Kuo, Hung‐Chi; Schubert, Wayne H.

doi:10.1175/2010mwr3102.1

Cited by 7 publications

(8 citation statements)

References 21 publications

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“…These rapid changes occur in such processes as breakdown of a quasilinear PV strip and separation of the TC and wave. In a recent study, Tsai et al (2010) derived a version of the Okubo-Weiss filamentation time for three-dimensional divergent flow constrained by material conservation of isentropic PV. Adapting their formulation and neglecting the effect of Earth's curvature (given the proximity to the equator), the filamentation time is written as…”

Section: Datamentioning

confidence: 99%

“…where d, S, and z refer to divergence, total deformation, and relative vorticity on an isentropic surface respectively. As noted in Tsai et al (2010), the formulation is defined only for strain-dominated regions, and small values of this diagnostic indicate rapid increase in PV gradient and potential for cutoff low formation. Tsai et al (2010) examined three cases of PV filamentation of upper-level troughs, including one in the tropics.…”

Section: Datamentioning

confidence: 99%

“…As noted in Tsai et al (2010), the formulation is defined only for strain-dominated regions, and small values of this diagnostic indicate rapid increase in PV gradient and potential for cutoff low formation. Tsai et al (2010) examined three cases of PV filamentation of upper-level troughs, including one in the tropics. While the applicability of the filamentation time defined above is questionable when nonconservative processes are present, some insight in AEW evolution can be gained in areas away from active convection.…”

Section: Datamentioning

confidence: 99%

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Evolution of African Easterly Waves in Potential Vorticity Fields

Tyner

Aiyyer

2012

Monthly Weather Review

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The evolution of African easterly waves (AEWs) leading to tropical cyclones (TCs) in the Atlantic during 2000–08 is examined from isentropic potential vorticity (PV) and Lagrangian streamline perspectives. Tropical cyclone formation is commonly preceded by axisymmetrization of PV, scale contraction of the wave, and formation of a closed circulation within the wave. In these cases, PV associated with the synoptic-scale wave is irreversibly deformed and subsumed within the developing vortex. Less commonly, filamentation of the PV leads to separation and independent propagation of the wave and the TC vortex. In an example presented here, the remnant wave with a closed circulation persisted for several days after separation from the TC. A second TC did not result, consistent with several past studies that show that a midtropospheric closed gyre is not sufficient for TC genesis. Sometimes, an AEW and a weak TC remain coupled for a few days, followed by the dissipation of the TC and the continued propagation of the wave. Merger of tropical and extratropical PV anomalies is also often observed and likely helps maintain some waves. The results of this study are broadly consistent with recent Lagrangian analyses of AEW evolution during TC genesis.

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Section: Datamentioning

confidence: 99%

Section: Datamentioning

confidence: 99%

Section: Datamentioning

confidence: 99%

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Evolution of African Easterly Waves in Potential Vorticity Fields

Tyner

Aiyyer

2012

Monthly Weather Review

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“…Finally, the piecewise PV inversion reveals further that the barotropic flow exerted a strong deformation on the upstream flank of the trough beginning on 8 October (quantified by a filamentation time‐scale as in Tsai et al , ; Riemer and Jones, 2013, not shown). It is thus plausible to assume that the high‐amplitude ridge upstream of the trough was instrumental for the trough's evolution into an elongated feature.…”

Section: Large‐scale Dynamics and Predictabilitymentioning

confidence: 67%

Dynamics of a local Alpine flooding event in October 2011: moisture source and large‐scale circulation

Piaget

Froidevaux

Giannakaki

et al. 2014

Quart J Royal Meteoro Soc

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Alpine heavy precipitation events often affect small catchments, although the circulation pattern leading to the event extends over the entire North Atlantic. The various For the first time, this study documents an important pathway for Northern Alpine flooding, in which the interaction of synoptic-scale to large-scale weather systems and of long-range moisture transport from the Tropics are dominant. Moreover, the trapping of moisture in a subtropical cut-off near the West African coast is found to be a crucial precursor to the observed European high impact weather.

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“…Conversely, in the "vorticity-dominated regions", the vorticity exceeds the deformation ( E 2 < 2 ), and the fluid is in an elliptical mode of motion that advects the vorticity smoothly. The Okubo-Weiss criterion has been used to explain some phenomena in atmosphere such as the trough thinning and filamentation in tropical cyclones (Rozoff et al 2006;Wang 2008;Tsai et al 2010). It indicates that different values of deformation and vorticity could construct different flow patterns (deformation dominated or vorticity dominated) which then endure different weather developments.…”

Section: Physical Meanings Of the Interactions Of Sv/sd And Sementioning

confidence: 99%

On the interactions of vorticity, divergence and deformation in a meso-α-scale vortex

Ran

Gao

2019

Meteorol Atmos Phys

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Vorticity, divergence and deformation are three differentiation properties of the air flow. In this paper, by deriving the tendency equations of squared vorticity (SV), squared divergence (SD) and squared deformation (SE), it is found that the three properties can interact with each other through the terms with opposite signs in the equations. These opposite-sign terms permit a quantitative discussion on the interactions between vorticity, divergence and deformation, and the role of these interactions on weather developments. The corresponding framework is first applied to investigate the development of an extratropical meso-α-scale cyclonic vortex in China. Through diagnosing the SV equation and the interactive terms in the vortex event, it is found that the interaction between SV and SD was the controlling factor for the evolution of the vortex. The transition of SD-SV can intensify the vortex, while the transition of SV-SD causes the vortex to die out. This is consistent with the relation between vorticity and divergence that has been obtained from the vertical vorticity equation. Apart from this, a new finding is that deformation also plays a role in influencing the vortex development. On one hand, deformation can interact with vorticity to affect the vortex directly. On the other hand, deformation interacts with divergence and influence the vortex development in an indirect way. These results provide a new insight on the vortex development which is worth further investigating in the future. D G J J D J J D G J J Land SeaPublisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Filamentation Time Diagnosis of Thinning Troughs and Cutoff Lows

Cited by 7 publications

References 21 publications

Evolution of African Easterly Waves in Potential Vorticity Fields

Evolution of African Easterly Waves in Potential Vorticity Fields

Dynamics of a local Alpine flooding event in October 2011: moisture source and large‐scale circulation

On the interactions of vorticity, divergence and deformation in a meso-α-scale vortex

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