Dynamics of Closed Systems of Resonantly Interacting Equatorial Waves

Arthur Z. Loesch National Center for Atmospheric Research, Boulder, CO 80307

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Richard C. Deininger National Center for Atmospheric Research, Boulder, CO 80307

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Abstract

Nonlinear dynamics of equatorial waves, interacting resonantly in coupled triad configurations which form closed systems, are investigated in the context of the divergents β-plane model. Closure is attained by demanding that spatial structures of the modes obey the atmospheric constraints. At larger fluid depths the wave systems are relatively small and concentrated at the smaller wavenumbers; at small depths the systems are larger and spread more widely in the wavenumber domain. Strong energy transfers in a system are consistently associated with modes characterized by the maximum frequency in individual triads. The lower frequency modes are energetically less active, especially when their frequencies are much less than and amplitudes greater than those of the maximum frequency modes in the same triads.

Abstract

Nonlinear dynamics of equatorial waves, interacting resonantly in coupled triad configurations which form closed systems, are investigated in the context of the divergents β-plane model. Closure is attained by demanding that spatial structures of the modes obey the atmospheric constraints. At larger fluid depths the wave systems are relatively small and concentrated at the smaller wavenumbers; at small depths the systems are larger and spread more widely in the wavenumber domain. Strong energy transfers in a system are consistently associated with modes characterized by the maximum frequency in individual triads. The lower frequency modes are energetically less active, especially when their frequencies are much less than and amplitudes greater than those of the maximum frequency modes in the same triads.

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