Influence of Different Phases of Quasi-Biennial Oscillation on the Evolution of Polar Stratospheric Zonal Winds

Stratospheric zonal winds are disturbed by tropospheric forced planetary waves which modulate the quasi-biennial oscillation (QBO) in the northern hemisphere during winter. QBO is the quasi periodic oscillation of zonal winds in the lower stratosphere with an average recurrence of 28 months. QBO is mainly characterized by zonal mean circulation in the equatorial and low latitudes of middle atmosphere. Investigations indicate that although QBO is an equatorial oscillation there is a strong correlation between QBO and stratospheric polar wind patterns. Additionally, westerly and easterly phases of QBO alter the strength of these winds differently. During the westerly phase of QBO, northern stratospheric zonal winds are stronger whereas the easterly phase coincides with the weaker stratospheric zonal winds.

In this study, easterly and westerly zonal winds at 30hPa for the latitudes between 5°S and 5°N which characterize the westerly (QBO-W) and easterly (QBO-E) phases of the QBO is examined using CMIP5 MPI-ESM-MR RCP4.5 scenario for the years between 2006 and 2099 for winter. It is found that climatic changes in the zonally asymmetric zonal wind characteristics in both phases of QBO modulates the polar stratospheric zonal winds differently. A prominent wave-1 structure in QBO-E phase and a wave-2 structure in QBO-W phase are apparent and effect the strength of the polar stratospheric zonal winds.

This study is a supported by TUBİTAK (The Scientific and Technology Research Council of Turkey), The Scientific and Technological Research Projects Funding Program, 1001.The project number is 117Y327.