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タイトル: | Angular distribution of energy spectrum in two-dimensional β-plane turbulence in the long-wave limit |
著者: | Saito, Izumi Ishioka, Keiichi |
著者名の別形: | 齋藤, 泉 |
キーワード: | Coriolis force numerical analysis ocean waves Rossby waves turbulence, vortices |
発行日: | 18-Jul-2013 |
出版者: | AIP Publishing LLC |
誌名: | Physics of Fluids |
巻: | 25 |
号: | 7 |
論文番号: | 076602 |
抄録: | The time-evolution of two-dimensional decaying turbulence governed by the long-wave limit, in which L_{D}IL → 0, of the quasi-geostrophic equation is investigated numerically. Here, LD is the Rossby radius of deformation, and L is the characteristic length scale of the flow. In this system, the ratio of the linear term that originates from the β-term to the nonlinear terms is estimated by a dimensionless number, γ = βL_{D}^{2}IU, where β is the latitudinal gradient of the Coriolis parameter, and U is the characteristic velocity scale. As the value of γ increases, the inverse energy cascade becomes more anisotropic. When γ ⩾ 1, the anisotropy becomes significant and energy accumulates in a wedge-shaped region where |I|>{√3}|k| in the two-dimensional wavenumber space. Here, k and I are the longitudinal and latitudinal wavenumbers, respectively. When γ is increased further, the energy concentration on the lines of I = ±{√3}K is clearly observed. These results are interpreted based on the conservation of zonostrophy, which is an extra invariant other than energy and enstrophy and was determined in a previous study. Considerations concerning the appropriate form of zonostrophy for the long-wave limit and a discussion of the possible relevance to Rossby waves in the ocean are also presented. |
著作権等: | © 2013 AIP Publishing LLC |
URI: | http://hdl.handle.net/2433/178670 |
DOI(出版社版): | 10.1063/1.4813808 |
出現コレクション: | 学術雑誌掲載論文等 |
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