ENSO Modoki Impacts on the Interannual Variations of Spring Antarctic Stratospheric Ozone

Using observation and reanalysis data, we investigated the effect of the sea surface temperature anomalies associated with ENSO Modoki from September to October on interannual variations in Antarctic stratospheric ozone from October to November. It was found that the planetary wave anomalies generated by ENSO Modoki in the tropical troposphere propagate to the southern mid-and then high-latitude stratosphere. The planetary wave anomalies have a pro-found impact on the polar vortex, subsequently affecting the interannual variations in Antarctic stratospheric ozone. Fur-ther analysis revealed that the responses of the polar vortex and ozone to ENSO Modoki are mainly modulated by the wave-1 and wave-3 components, and the effect of wave 2 is opposite and offset by those of wave 1 and wave 3. The contri-bution of the residual waves (after removing waves 1, 2, 3, and the remaining waves) are relatively small. Furthermore, we evaluated the performance of CMIP6 models in simulating the impacts of ENSO Modoki on the southern stratospheric po-lar vortex and ozone. We selected seven models that include stratospheric processes and stratospheric chemical ozone. We found that all are capable of distinguishing between eastern Pacific ENSO and ENSO Modoki events. However, only GISS-E2-1-G and MPI-ESM-1-2-HAM can simulate the patterns of ozone, circulation, and temperature in the Southern Hemisphere in a manner that closely resembles the reanalysis results. Further analysis indicated that these two models can better simulate the propagation of planetary wave activities in the troposphere forced by ENSO Modoki, whereas the other models produce significantly different results to those obtained from observations.SIGNIFICANCE STATEMENT: This study found a significant connection between ENSO Modoki and the interannual variability of Antarctic stratospheric ozone in austral spring and investigated the underlying physical mechanisms in detail. In addition, the performances of CMIP6 models in simulating the impact of ENSO Modoki on the southern stratospheric polar vortex and ozone were evaluated. This study not only helps to further understand the characteristics of past Antarctic ozone changes but also helps developers improve the performance of models in simulating Antarctic stratospheric changes.

Automated summary

This study investigated the impact of ENSO Modoki on Antarctic stratospheric ozone variability in austral spring using observation and reanalysis data. It found that ENSO Modoki generates planetary wave anomalies in the troposphere, which subsequently affect the polar vortex and interannual variations in Antarctic stratospheric ozone. Analysis also revealed that wave-1 and wave-3 components play a significant role, while wave-2 effects are opposite and offset by waves 1 and 3. Furthermore, the study evaluated the performance of CMIP6 models in simulating the impacts of ENSO Modoki on the southern stratospheric polar vortex and ozone, finding that only two models closely resemble the reanalysis results.