Vertical structure of MJO-related subtropical ozone variations from MLS, TES, and SHADOZ data

Tian et al. (2007) found that the MJO-related total column ozone (O3 ) anomalies of 10 DU (peak-to-trough) are mainly evident over the subtropics and dynamically driven by the vertical movement of the subtropical tropopause layer. It was then hypothesized that the subtropical total column O3 anomalies are primarily associated with the O3 variability in the stratosphere rather the troposphere. In this paper, we investigate the vertical structure of MJO-related subtropical O3 variations using the vertical O3 profiles from the Aura Microwave Limb Sounder (MLS) and Tropospheric Emission Spectrometer (TES), as well as in-situ measurements by the Southern Hemisphere Additional Ozonesondes (SHADOZ) project. Our analysis indicates that the subtropical O3 anomalies maximize approximately in the lower stratosphere (60–100 hPa). Furthermore, the spatialtemporal patterns of the subtropical O3 anomalies in the lower stratosphere are very similar to that of the total column. In particular, they are both dynamically driven by the vertical movement of subtropical tropopause. The subtropical partial O3 column anomalies between 30–200 hPa accounts for more than 50 % of the total O3 column anomalies. TES measurements show that at most 27 % of the total O3 column anomalies are contributed by the tropospheric components. This indicates that the subtropical total column O3 anomalies are mostly from the O3 anomalies in the lower stratosphere, which supports the hypothesis of Tian et al. (2007). The strong connection between the intraseasonal subtropical stratospheric O3 variations and the MJO implies that the stratospheric O3 variations may be predictable with similar lead times over the subtropics. Future work could involve a similar study or an O3 budget analysis using a sophisticated chemical transport model in the near-equatorial regions where the observed MJO signals of total column O3 are weak.