Energetics Analysis of a Multilevel Global Spectral Model. Part II: Zonal and Meridional Gravitational Energy

Shun Der Ko National Center for Atmospheric Research, Boulder, Colorado

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Joseph J. Tribbia National Center for Atmospheric Research, Boulder, Colorado

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John P. Boyd Department of Atmospheric, Oceanic, and Space Science. The University of Michigan, Ann Arbor, Michigan

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Abstract

A new approach to energetics is introduced and applied to the NCAR Community Climate Model. All the energy components are separated into gravitational and rotational parts. The new feature of our scheme is that the gravitational divergent kinetic energy is further decoupled into zonal and meridional components, which measure the strength of the cut-west and meridional circulations, respectively. The zonal and meridional nondivergent kinetic energies represent the vorticities related to the nondivergent zonal and meridional winds, respectively. The distributions of energy among meridional indices, vertical modes, and zonal waves are analyzed.

We suggest a new, easy, and reasonable criterion to adjust the gravity waves in the initialization based on the vertical modes, meridional indices, and zonal wavenumbers. To retain the strength of large-scale circulations and to preserve the intensity of synoptic scale pressure systems, we recommend that the gravity waves corresponding to the internal modes 2–6, meridional indices 1–6, and zonal wavenumbers 1–10 not be adjusted significantly during the initialization. However, all the other gravity waves can be adjusted initially, particularly those associated with the external and the first internal modes.

Abstract

A new approach to energetics is introduced and applied to the NCAR Community Climate Model. All the energy components are separated into gravitational and rotational parts. The new feature of our scheme is that the gravitational divergent kinetic energy is further decoupled into zonal and meridional components, which measure the strength of the cut-west and meridional circulations, respectively. The zonal and meridional nondivergent kinetic energies represent the vorticities related to the nondivergent zonal and meridional winds, respectively. The distributions of energy among meridional indices, vertical modes, and zonal waves are analyzed.

We suggest a new, easy, and reasonable criterion to adjust the gravity waves in the initialization based on the vertical modes, meridional indices, and zonal wavenumbers. To retain the strength of large-scale circulations and to preserve the intensity of synoptic scale pressure systems, we recommend that the gravity waves corresponding to the internal modes 2–6, meridional indices 1–6, and zonal wavenumbers 1–10 not be adjusted significantly during the initialization. However, all the other gravity waves can be adjusted initially, particularly those associated with the external and the first internal modes.

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