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Geophysical Research Letters

Spontaneous QBO-like oscillations in an atmospheric model dynamical core

Authors

  • Weiye Yao,

    Corresponding author
    1. Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA
    • Corresponding author: W. Yao, Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, 2455 Hayward St, Ann Arbor, MI 48109, USA. (weiyeyao@umich.edu)

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  • Christiane Jablonowski

    1. Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA
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Abstract

[1] The ability of general circulation models (GCMs) to simulate the quasi-biennial oscillation (QBO) is an important model characteristic. Typically, the moist convective parameterization is believed to be the key GCM component that triggers tropical waves, thereby forcing wave-mean flow interactions. We show that QBO-like oscillations can also be simulated in a dry dynamical core driven by the Held-Suarez forcing. No gravity wave drag parameterization is applied. The simulations utilize the semi-Lagrangian spectral transform dynamical core of National Center for Atmospheric Research's Community Atmosphere Model. The QBO-like signal has a long period between 42–45 months and occurs in the upper stratosphere; different from observations. However, the amplitudes, asymmetries, and meridional extent closely resemble the observed QBO. Wave-number frequency analysis shows that resolved equatorially trapped waves are abundant despite the absence of cumulus convection. A Transformed Eulerian-Mean analysis suggests that the divergence of the Eliassen-Palm flux and vertical advection provide most of the forcing counteracted by diffusion.

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