[A-AS09] Stratosphere-troposphere Processes And their Role in Climate

[AAS09-P13] Analyses of interannual variation of middle atmopsheric ozone and other minor substances using the digital filter model.

*Tianliang Yang^1,2, Tomoo Nagahama², Tac Nakajima² (1.Graduate School of Science, Nagoya University, 2.Institute for Space-Earth Environmental Research, Nagoya University)

Keywords:QBO effects, stratospheric minor substances , Interannual variation, Digital filter

The Quasi-Biennial Oscillation (QBO) is a periodic fluctuation in the stratosphere's equatorial winds, typically occurring over 26 to 29 months. The QBO has a significant effect on stratospheric ozone. Although the QBO-induced effects are mainly restricted within the tropics, The QBO also impacts the ozone in the polar regions. During the positive phase of the QBO, the easterly winds at the equator can push ozone-poor air to higher latitudes, decreasing ozone concentration in the polar regions. Conversely, during the negative phase, the westerly winds at the equator can transport ozone-rich air from lower latitudes to the poles, increasing ozone concentration in the polar regions. In this study, we utilized the digital filter (DF) to analyze the period characteristic of global stratospheric ozone in 2-to-5-year components. Apart from the QBO ozone with amplitudes of about 0.6 ppm, consistent with the previous study, the QBO-like amplitudes in the polar regions are also detected with amplitudes of 0.4~0.5 ppm. As for the possible mechanisms in the polar regions, the monthly-mean interannual polar indices (Arctic Oscillation (AO) or North Atlantic Oscillation (NAO) in the northern polar region and Antarctic Oscillation (AAO) in the southern polar region) are exhibited. Limited as the data available, the correlation between the QBO-like amplitudes in the north polar and the negative phase of the indices, which denotes the anomalous pressure condition of the polar, can be seen. Besides, the QBO-like signals detected by the DF model can also be seen from the HCl and N₂O that are anti-phase with each other near the equator. This is because of the different dynamics between them. N₂O is relatively inert and does not contribute directly to stratospheric ozone depletion, but it can act as a precursor for the production of active nitrogen compounds that can lead to the destruction of ozone in the stratosphere, while HCl serves as the Chlorine reservoir in the stratosphere. Besides, the HCl and N₂O QBO-like signals in polar regions are also asymmetry. In the lower stratosphere over the north polar, QBO amplitudes remain relatively constant and exhibit a synchronized phase during QBO-like ozone periods, while the correlation cannot be seen in the south polar. Furthermore, when comparing the DF outputs of different measurements from the satellite data, for example, the temperature and the ozone, the interannual variation of the DF outputs can be attributed to the thermodynamics model. Considering that the DF model has yet to be applied to the stratospheric analyses, and unprecedented results are found via the method, this can offer a new perspective on the stratospheric ozone interannual variation