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A QBO cookbook: Sensitivity of the Quasi-Biennial Oscillation to resolution, resolved waves, and parameterized gravity waves
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  • Chaim I Garfinkel,
  • Edwin P Gerber,
  • Ofer Shamir,
  • Jian Rao,
  • Martin Jucker,
  • Ian Philip White,
  • Nathan Paldor
Chaim I Garfinkel
Hebrew University of Jerusalem

Corresponding Author:[email protected]

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Edwin P Gerber
New York University
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Ofer Shamir
Hebrew University of Jerusalem
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Jian Rao
Nanjing University of Information Science and Technology
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Martin Jucker
University of New South Wales
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Ian Philip White
Hebrew University of Jerusalem
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Nathan Paldor
Hebrew University of Jerusalem
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Abstract

An intermediate complexity moist General Circulation Model is used to investigate the sensitivity of the Quasi-Biennial Oscillation (QBO) to resolution, diffusion, tropical tropospheric waves, and parameterized gravity waves. Finer horizontal resolution is shown to lead to a shorter period, while finer vertical resolution is shown to lead to a slower period and to an accelerated amplitude in the lowermost stratosphere. More scale-selective diffusion leads to a faster and stronger QBO, while enhancing the sources of tropospheric stationary wave activity leads to a weaker QBO. In terms of parameterized gravity waves, broadening the spectral width of the source function leads to a longer period and a stronger amplitude although the amplitude effect saturates when the half-width exceeds $\sim25$m/s. A stronger gravity wave source stress leads to a faster and stronger QBO, and a higher gravity wave launch level leads to a stronger QBO. All of these sensitivities are shown to result from their impact on the resultant wave-driven momentum torque in the tropical stratosphere. Atmospheric models have struggled to accurately represent the QBO, particularly at moderate resolutions ideal for long climate integrations. In particular, capturing the amplitude and penetration of QBO anomalies into the lower stratosphere (which has been shown to be critical for the tropospheric impacts) has proven a challenge. The results provide a recipe to generate and/or improve the simulation of the QBO in an atmospheric model.
Mar 2022Published in Journal of Advances in Modeling Earth Systems volume 14 issue 3. 10.1029/2021MS002568