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Seasonality of the QBO Impact on Equatorial Clouds
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  • Aodhan John Sweeney,
  • Qiang Fu,
  • Hamid A. Pahlavan,
  • Peter Haynes
Aodhan John Sweeney
University of Washington

Corresponding Author:[email protected]

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Qiang Fu
University of Washington
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Hamid A. Pahlavan
University of Washington
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Peter Haynes
University of Cambridge
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Abstract

The Quasi-Biennial Oscillation (QBO) dominates the interannual variability in the tropical lower stratosphere and is characterized by the descent of alternating easterly and westerly zonal winds. The QBO impact on tropical clouds and convection has received great attention in recent years due to its implications for weather and climate. In this study, a 15-year record of high vertical resolution observations from CALIPSO are used to document the QBO impact on equatorial (10°S-10°N) clouds. Observations from radio occultations, the CERES instrument, and the ERA5 reanalysis are also used to document the QBO impact on temperature, radiative energy budget, and zonal wind. It is shown that the QBO impact on zonal mean equatorial cloud fraction has a strong seasonality. The strongest cloud fraction response to the QBO occurs in boreal spring and early summer extending down to ~12 km and results in a significant longwave cloud radiative effect anomaly. The seasonality of the cloud fraction changes is synchronized with those of temperature and zonal wind in the tropical upper troposphere.