Mesoscale Horizontal Kinetic Energy Spectra of a Tropical Cyclone

Wang, Yuan; Zhang, Lifeng; Peng, Jun; Liu, Saisai

doi:10.1175/jas-d-17-0391.1

Cited by 10 publications

(29 citation statements)

References 37 publications

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“…The traditional way to study the role of eddies in vortex formation or intensification is to diagnose the radial transport of vorticity by eddies (Hendricks et al 2004;Montgomery et al 2006), or check the energy cascade direction (e.g. Vallis et al 1997;Wang et al 2018). We propose a way to partly circumvent the turbulent process.…”

Section: ) the Evolution Of Eddiesmentioning

confidence: 99%

The role of random vorticity stretching in tropical depression genesis

Hao¹,

O’Neill²

2021

Preprint

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Tropical deep convection plays a key role at the tropical depression stage of tropical cyclogenesis by aggregating vorticity, but no existing theory can depict such a stochastic vorticity aggregation process. Vorticity probability distribution function (PDF) is proposed as a tool to predict the horizontal structure and wind speed of the tropical depression, a tropical cyclone in its early stage. The reason lies in the tendency for a vortex to adjust to an axisymmetric and monotonic vorticity structure. Assuming deep convection as independent and uniformly distributed vortex tube stretching events in the lower troposphere, repetitive vortex tube stretching will make the air column area shrink many times and significantly increase vorticity. A theory of vorticity PDF is established by modelling the random stretching process as a Markov chain. The PDF turns out to be a weighted Poisson distribution, in good agreement with a randomly-forced divergent barotropic model (weak temperature gradient model), and in rough agreement with a cloud-permitting simulation. The result shows that a strong and sparse deep convective mode tends to produce more high vorticity air columns, which favors tropical cyclogenesis.

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Section: ) the Evolution Of Eddiesmentioning

confidence: 99%

The role of random vorticity stretching in tropical depression genesis

Hao¹,

O’Neill²

2021

Preprint

View full text Add to dashboard Cite

show abstract

“…The traditional way to study the role of eddies in vortex formation or intensification is to diagnose the radial transport of vorticity by eddies (Hendricks et al 2004;Montgomery et al 2006), or check the energy cascade direction (e.g. Vallis et al 1997;Wang et al 2018). We propose a 18 Accepted for publication in Journal of the Atmospheric Sciences.…”

Section: ) the Evolution Of Eddiesmentioning

confidence: 99%

The Role of Random Vorticity Stretching in Tropical Depression Genesis

O’Neill

2021

Journal of the Atmospheric Sciences

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Tropical deep convection plays a key role in the tropical depression stage of tropical cyclogenesis by aggregating vorticity, but no existing theory can depict such a stochastic vorticity aggregation process. A vorticity probability distribution function (PDF) is proposed as a tool to predict the horizontal structure and wind speed of the tropical depression. The reason lies in the tendency for a vortex to adjust to an axisymmetric and monotonic vorticity structure. Assuming deep convection as independent and uniformly distributed vortex tube stretching events in the low-mid troposphere, repetitive vortex tube stretching will make the air column area shrink many times and significantly increase vorticity. A theory of the vorticity PDF is established by modelling the random stretching process as a Markov chain. The PDF turns out to be a weighted Poisson distribution, in good agreement with a randomly-forced divergent barotropic model (weak temperature gradient model), and in rough agreement with a cloud-permitting simulation. The result shows that a stronger and sparser deep convective mode tends to produce more high vorticity air columns, which leads to a more compact major vortex with a higher maximum wind. Based on the vorticity PDF theory, a parameterization of the eddy acceleration effect on the tangential flow is proposed.

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“…In fact, in a f − plane study, Waite and Snyder (2013) noted that injection of energy due to latent heating enhanced the role of divergent components in moist baroclinic waves. On the other hand, numerical simulations of tropical cyclones showed a forward energy transfer and −5/3 KE power-law dominated by rotational modes, at scales below 500 km in the upper troposphere (Wang et al, 2018). But, in situ aircraft data taken from flights through hurricanes paint a more diverse picture with mesoscale slopes going from −5/3 to −3 depending on the strength of systems (Vonich and Hakim, 2018).…”

Section: Introductionmentioning

confidence: 99%

Turbulence and equatorial waves in moist and dry shallow water systems

Schröttle¹,

Suhas²,

Harnik³

et al. 2021

Preprint

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Turbulence and large-scale waves in the tropical region are studied using the spherical shallow water equations. With mesoscale vorticity forcing, both moist and dry systems show kinetic energy scaling that is dominated by rotational modes, has a −5/3 exponent.At larger planetary scales, the divergent component of the energy increases and we see a footprint of tropical waves. The dry system shows a signature of the entire family of equatorial waves, while the moist simulations only show low frequency Rossby, Kelvin and mixed Rossby gravity waves with an equivalent depth that matches rapid condensation estimates. Further, runs with interactive moisture exhibit spontaneous aggregation with the equilibrium moist energy spectrum obeying a −2 power-law. Synoptic scale moisture anomalies form in heterogeneous background saturation, and are sustained by advection and convergence, within rotational gyres that dominate the tropical region. In that case, along with equatorial waves and turbulence, a large-scale eastward moving moisture wave appears in the midlatitudes. In all simulations with upscale energy transfer, a systematic equatorial zonal mean zonal flow develops which is easterly and westerly for the dry and moist ensembles, respectively. The interaction of this zonal mean flow with a spatially heterogeneous saturation field results in the formation of a moist stationary tropical wave. The super-rotating flow is driven by rotational eddy momentum fluxes due to enhanced equatorial Rossby wave activity in the moist runs. Interestingly, even though Kelvin waves are more energetic in the dry simulations, the easterly momentum flux is also due to rotational eddy fluxes. The nature of eddies is such that the tropical circulation in the dry and moist cases tends to homogenize and exaggerate potential vorticity gradients, respectively. These experiments demonstrate the co-existence of tropical waves and turbulence, and highlight the fact that the vortical and divergent wind are inextricably linked with the evolving moisture field.

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Mesoscale Horizontal Kinetic Energy Spectra of a Tropical Cyclone

Cited by 10 publications

References 37 publications

The role of random vorticity stretching in tropical depression genesis

The role of random vorticity stretching in tropical depression genesis

The Role of Random Vorticity Stretching in Tropical Depression Genesis

Turbulence and equatorial waves in moist and dry shallow water systems

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