Arctic stratospheric ozone as a precursor of ENSO events since 2000s

Recent depletion of the Arctic Stratospheric Ozone (ASO) has raised significant concerns about its impact on surface climate and weather. By analyzing observational reanalysis dataset and the Ozone Monitoring Instrument, here we found that the relevant variations in springtime ASO can be a potential precursor of El Niño–Southern Oscillation in the subsequent winter since 2000s. During this period, springtime ASO variability become pronounced, particularly over the Eurasian continent, due to the asymmetrical structure of the Arctic stratospheric polar vortex. With the return of solar radiation to the Arctic in spring, increased ASO leads to more absorption of solar radiation over Eurasia, contributing to localized anomalous heating. This stratospheric heating induces upper-tropospheric cyclonic circulation over Siberia, resulting in the propagation of atmospheric stationary waves toward the tropical Pacific. As a result, upper-level easterly and low-level westerly wind anomalies emerge over the equatorial Pacific. This baroclinic atmospheric anomaly over the equatorial Pacific promotes El Niño development by modulating the Walker circulation (c.f., La Niña for the opposite case). These results highlight the critical role of chemical-radiative-dynamical processes in the Arctic stratosphere for understanding surface climate phenomena.