Modulation and dynamics of the Quasi-Biennial Oscillation associated with El Nino/Southern Oscillation

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Using atmospheric reanalysis and CMIP5 datasets, this study investigated modulation and dynamics of the Quasi-Biennial Oscillation (QBO) in the equatorial stratosphere. In particular, we found that in the reanalysis data, the QBO modulation associated with the mean seasonal cycle and El Nino/Southern Oscillation (ENSO) is not explained by large-scale fields. It was also found that QBO-like oscillations, simulated in a few CMIP5 models, have notable differences in structure and behavior from the real world. These suggest that small-scale waves (gravity waves) are important in the modulation.We further revealed nonlinear changes in frequency of major stratospheric sudden warmings with QBO and ENSO using a long reanalysis dataset.