### Abstract

Inertia-gravity wave (IGW) radiation from the elliptical vortex is investigated in the f-plane shallow water system. The far field of IGW is analytically derived for the case of an almost circular Kirchhoff vortex with a small aspect ratio. Cyclone-anticyclone asymmetry appears at finite values of the Rossby number (Ro) caused by the source originating in the Coriolis acceleration. While the intensity of IGWs from the cyclone monotonically decreases as f increases, that from the anticyclone increases as f increases for relatively smaller f and has a local maximum at intermediate f. A numerical experiment is conducted on a model using a spectral method in an unbounded domain. The numerical results agree quite well with the analytical ones for elliptical vortices with small aspect ratios, implying that the derived analytical forms are useful for the verification of the numerical model. For elliptical vortices with larger aspect ratios, however, significant deviation from the analytical estimates appears. The intensity of IGWs radiated in the numerical simulation is larger than that estimated analytically. The reason is that the source of IGWs is amplified during the time evolution because the shape of the vortex changes from ideal ellipse to elongated with filaments. Nevertheless, cyclone-anticyclone asymmetry similar to the analytical estimate appears in all the range of aspect ratios, suggesting that this asymmetry is a robust feature.

Original language | English |
---|---|

Article number | 025508 |

Journal | Fluid Dynamics Research |

Volume | 49 |

Issue number | 2 |

DOIs | |

Publication status | Published - 2017 Feb 6 |

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### Keywords

- cyclone-anticyclone asymmetry
- Kirchhoff vortex
- Lighthill theory
- shallow water flows
- spontaneous gravity wave radiation

### ASJC Scopus subject areas

- Mechanical Engineering
- Physics and Astronomy(all)
- Fluid Flow and Transfer Processes

### Cite this

**Inertia-gravity wave radiation from the elliptical vortex in the f-plane shallow water system.** / Sugimoto, Norihiko.

Research output: Contribution to journal › Article

}

TY - JOUR

T1 - Inertia-gravity wave radiation from the elliptical vortex in the f-plane shallow water system

AU - Sugimoto, Norihiko

PY - 2017/2/6

Y1 - 2017/2/6

N2 - Inertia-gravity wave (IGW) radiation from the elliptical vortex is investigated in the f-plane shallow water system. The far field of IGW is analytically derived for the case of an almost circular Kirchhoff vortex with a small aspect ratio. Cyclone-anticyclone asymmetry appears at finite values of the Rossby number (Ro) caused by the source originating in the Coriolis acceleration. While the intensity of IGWs from the cyclone monotonically decreases as f increases, that from the anticyclone increases as f increases for relatively smaller f and has a local maximum at intermediate f. A numerical experiment is conducted on a model using a spectral method in an unbounded domain. The numerical results agree quite well with the analytical ones for elliptical vortices with small aspect ratios, implying that the derived analytical forms are useful for the verification of the numerical model. For elliptical vortices with larger aspect ratios, however, significant deviation from the analytical estimates appears. The intensity of IGWs radiated in the numerical simulation is larger than that estimated analytically. The reason is that the source of IGWs is amplified during the time evolution because the shape of the vortex changes from ideal ellipse to elongated with filaments. Nevertheless, cyclone-anticyclone asymmetry similar to the analytical estimate appears in all the range of aspect ratios, suggesting that this asymmetry is a robust feature.

AB - Inertia-gravity wave (IGW) radiation from the elliptical vortex is investigated in the f-plane shallow water system. The far field of IGW is analytically derived for the case of an almost circular Kirchhoff vortex with a small aspect ratio. Cyclone-anticyclone asymmetry appears at finite values of the Rossby number (Ro) caused by the source originating in the Coriolis acceleration. While the intensity of IGWs from the cyclone monotonically decreases as f increases, that from the anticyclone increases as f increases for relatively smaller f and has a local maximum at intermediate f. A numerical experiment is conducted on a model using a spectral method in an unbounded domain. The numerical results agree quite well with the analytical ones for elliptical vortices with small aspect ratios, implying that the derived analytical forms are useful for the verification of the numerical model. For elliptical vortices with larger aspect ratios, however, significant deviation from the analytical estimates appears. The intensity of IGWs radiated in the numerical simulation is larger than that estimated analytically. The reason is that the source of IGWs is amplified during the time evolution because the shape of the vortex changes from ideal ellipse to elongated with filaments. Nevertheless, cyclone-anticyclone asymmetry similar to the analytical estimate appears in all the range of aspect ratios, suggesting that this asymmetry is a robust feature.

KW - cyclone-anticyclone asymmetry

KW - Kirchhoff vortex

KW - Lighthill theory

KW - shallow water flows

KW - spontaneous gravity wave radiation

UR - http://www.scopus.com/inward/record.url?scp=85015744930&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85015744930&partnerID=8YFLogxK

U2 - 10.1088/1873-7005/aa529e

DO - 10.1088/1873-7005/aa529e

M3 - Article

AN - SCOPUS:85015744930

VL - 49

JO - Fluid Dynamics Research

JF - Fluid Dynamics Research

SN - 0169-5983

IS - 2

M1 - 025508

ER -