# Cyclone-anticyclone asymmetry in gravity wave radiation from a co-rotating vortex pair in rotating shallow water

Research output: Contribution to journalArticle

4 Citations (Scopus)

### Abstract

Cyclone-anticyclone asymmetry in spontaneous gravity wave radiation from a co-rotating vortex pair is investigated in an $f$-plane shallow water system. The far field of gravity waves is derived analytically by analogy with the theory of aeroacoustic sound wave radiation (Lighthill theory). In the derived form, the Earth's rotation affects not only the propagation of gravity waves but also their source. While the results correspond to the theory of vortex sound in the limit of $f\rightarrow 0$, there is an asymmetry in gravity wave radiation between cyclone pairs and anticyclone pairs for finite values of $f$. Anticyclone pairs radiate gravity waves more intensely than cyclone pairs due to the effect of the Earth's rotation. In addition, there is a local maximum of intensity of gravity waves from anticyclone pairs at an intermediate $f$. To verify the analytical solution, a numerical simulation is also performed with a newly developed spectral method in an unbounded domain. The novelty of this method is the absence of wave reflection at the boundary due to a conformal mapping and a pseudo-hyperviscosity that acts like a sponge layer in the far field of waves. The numerical results are in excellent agreement with the analytical results even for finite values of $f$ for both cyclone pairs and anticyclone pairs.

Original language English 80-106 27 Journal of Fluid Mechanics 772 https://doi.org/10.1017/jfm.2015.209 Published - 2015 Jun 1

### Fingerprint

anticyclones
cyclones
Gravity waves
shallow water
gravity waves
Vortex flow
asymmetry
vortices
Water
Earth rotation
far fields
Earth (planet)
Acoustic waves
Aeroacoustics
aeroacoustics
Conformal mapping
wave reflection
conformal mapping

### Keywords

• rotating flows
• shallow water flows
• waves in rotating fluids

### ASJC Scopus subject areas

• Mechanical Engineering
• Mechanics of Materials
• Condensed Matter Physics

### Cite this

In: Journal of Fluid Mechanics, Vol. 772, 01.06.2015, p. 80-106.

Research output: Contribution to journalArticle

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abstract = "Cyclone-anticyclone asymmetry in spontaneous gravity wave radiation from a co-rotating vortex pair is investigated in an $f$-plane shallow water system. The far field of gravity waves is derived analytically by analogy with the theory of aeroacoustic sound wave radiation (Lighthill theory). In the derived form, the Earth's rotation affects not only the propagation of gravity waves but also their source. While the results correspond to the theory of vortex sound in the limit of $f\rightarrow 0$, there is an asymmetry in gravity wave radiation between cyclone pairs and anticyclone pairs for finite values of $f$. Anticyclone pairs radiate gravity waves more intensely than cyclone pairs due to the effect of the Earth's rotation. In addition, there is a local maximum of intensity of gravity waves from anticyclone pairs at an intermediate $f$. To verify the analytical solution, a numerical simulation is also performed with a newly developed spectral method in an unbounded domain. The novelty of this method is the absence of wave reflection at the boundary due to a conformal mapping and a pseudo-hyperviscosity that acts like a sponge layer in the far field of waves. The numerical results are in excellent agreement with the analytical results even for finite values of $f$ for both cyclone pairs and anticyclone pairs.",
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AU - Ishioka, K.

AU - Kobayashi, Hiromichi

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