On a Quasi-Invariant Associated with the Emergence of Anisotropy in Two-Dimensional Turbulence on a Rotating Sphere

Journal of the Meteorological Society of Japan. Ser. II

Izumi SAITO¹  Keiichi ISHIOKA² 

[1] Department of Scientific and Engineering Simulation, Graduate School of Engineering, Nagoya Institute of Technology, Nagoya, Japan;Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Kyoto, Japan

关键词: large-scale planetary flow;    two-dimensional turbulence on a rotating sphere;    zonal flow;    zonostrophy;    quasi-invariant;   

DOI  :  10.2151/jmsj.2016-002

学科分类：大气科学

来源: Meteorological Society of Japan

【 摘 要 】

 To provide a theoretical explanation for the emergence of zonally elongated structures from two-dimensional turbulence on a rotating sphere, a quasi-invariant of the system is obtained by a minimization process, which is a straightforward extension of a similar process proposed by a previous study on β-plane turbulence to the spherical geometry. The quasi-invariant is defined as a weighted sum of the energy density in the wavenumber space. The distribution of the weighting coefficient has airfoil-shaped contours, with which the anisotropic energy transfer that favors zonally elongated structures can be explained. Large number of numerical time-integrations of decaying two-dimensional turbulence on a rotating sphere are conducted to examine the conservation of the quasi-invariant. It is shown that the quasi-invariant is conserved well when the nonlinearity of the system is sufficiently weak; furthermore, energy is transferred in the wavenumber space apparently along the airfoil-shaped contours of the weighting coefficient for the quasi-invariant.

【 授权许可】

Unknown