Journal of Geophysical Research: Atmospheres

Influence of the quasi-biennial oscillation and El Niño–Southern Oscillation on the frequency of sudden stratospheric warmings


  • Jadwiga H. Richter,

    1. Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, Colorado, USA
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  • Katja Matthes,

    1. Section 1.3: Earth System Modeling, Helmholtz Centre Potsdam, German Centre for Geosciences, Potsdam, Germany
    2. Institut für Meteorologie, Freie Universität Berlin, Berlin, Germany
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  • Natalia Calvo,

    1. Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA
    2. Dipartamento de Fisica de la Tierra II, Universidad Complutense de Madrid, Madrid, Spain
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  • Lesley J. Gray

    1. National Centre for Atmospheric Science, Oxford, UK
    2. Department of Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UK
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[1] Stratospheric sudden warmings (SSWs) are a major source of variability during Northern Hemisphere winter. The frequency of occurrence of SSWs is influenced by El Niño–Southern Oscillation (ENSO), the quasi-biennial oscillation (QBO), the 11 year solar cycle, and volcanic eruptions. This study investigates the role of ENSO and the QBO on the frequency of SSWs using the National Center for Atmospheric Research's Whole Atmosphere Community Climate Model, version 3.5 (WACCM3.5). In addition to a control simulation, WACCM3.5 simulations with different combinations of natural variability factors such as the QBO and variable sea surface temperatures (SSTs) are performed to investigate the role of QBO and ENSO. Removing only one forcing, variable SSTs or QBO, yields a SSW frequency similar to that in the control experiment; however, removing both forcings results in a significantly decreased SSW frequency. These results imply nonlinear interactions between ENSO and QBO signals in the polar stratosphere during Northern Hemisphere winter. This study also suggests that ENSO and QBO force SSWs differently. The QBO forces SSW events that are very intense and whose impact on the stratospheric temperature can be seen between December and June, whereas ENSO forces less intense SSWs whose response is primarily confined to the months of January, February, and March. The effects of SSWs on the stratospheric background climate is also addressed here.