EGU2020-5635, updated on 28 May 2020
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

An evaluation of tropical waves and wave forcing of the QBO in the QBOi models

Laura Holt1, Francois Lott2, and the QBOi Contributors*
Laura Holt and Francois Lott and the QBOi Contributors
  • 1NorthWest Research Associates, Boulder, CO, United States of America (
  • 2PSL research Institute, Ecole Normale Supérieure, Paris
  • *A full list of authors appears at the end of the abstract

We analyze the stratospheric waves in models participating in phase 1 of the Stratosphere–troposphere Processes And their Role in Climate (SPARC) Quasi-Biennial Oscillation initiative (QBOi). All models have robust Kelvin and mixed Rossby-gravity wave modes in winds and temperatures at and represent them better than most of the Coupled Model Intercomparison Project Phase 5 (CMIP5) models. There is still some spread among the models, especially concerning the mixed Rossby-gravity waves. We attribute the variability in equatorial waves among the QBOi models in part to the varying horizontal and vertical resolutions, to systematic biases in zonal winds, and to the considerable variability in convectively coupled waves in the troposphere among the models: only roughly half of the QBOi models have realistic convectively coupled Kelvin waves and only a few models have convectively coupled mixed Rossby-gravity waves. The models with stronger convectively coupled waves produce larger zonal mean forcing due to resolved waves in the QBO region. Finally we evaluate the Eliassen-Palm (EP) flux and EP flux divergence of the resolved waves in the QBOi models. We find that there is a large spread in the forcing from resolved waves in the QBO region, and the resolved wave forcing has a robust correlation with model vertical resolution

QBOi Contributors:

L. A. Holt, F. Lott, R. R. Garcia, G. N. Kiladis, J. A. Anstey, P. Braesicke, A. C. Bushell, N. Butchart, C. Cagnazzo, C.-C. Chen, H.-Y. Chun, Y. Kawatani, T. Kerzenmacher, Y.-H. Kim, C. McLandress, H. Nao, S. Osprey, J. H. Richter, A. A. Scaife, J. Scinocca, F. Serva, S. Versick, S. Watanabe, K. Yoshida, S. Yukimoto

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Presentation version 1 – uploaded on 28 Apr 2020
  • CC1: Comment on EGU2020-5635, Seok-Woo Son, 02 May 2020

    MIROC-AGCM-LL does have realistic QBO without gravity wave prameterization. Does it imply GW drag is not necessary in simulaiting QBO?

  • CC2: Comment on EGU2020-5635, Paul Pukite, 05 May 2020

    "MIROC-AGCM-LL does have realistic QBO without gravity wave prameterization. Does it imply GW drag is not necessary in simulaiting QBO?"

    How can QBO not require gravity wave parameterization?  The QBO cycle of 28 months is clearly an exact alignment with the lunar nodal gravitational cycle.  This is such a strong synchronizing force that even the QBO anomaly of 2015-2016 couldn't permanently disrupt the alignment, as it is now has synched back to the prior cycle.