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

Variability in Arctic stratospheric ozone (ASO) has significant implications for surface climate. Using observational reanalysis datasets and Ozone Monitoring Instrument data, we found that the springtime ASO variations since the 2000s can serve as a precursor to El Niño–Southern Oscillation in the subsequent winter. Springtime ASO variability has become pronounced, particularly over Eurasia, due to the asymmetric structure of the Arctic stratospheric polar vortex. With the return of solar radiation to the Arctic in spring, elevated ASO increases solar absorption over Eurasia, contributing to localized stratospheric heating. This heating induces an upper-tropospheric cyclonic circulation over Siberia, facilitating wave energy propagation toward the tropical Pacific. Consequently, upper-level easterly and low-level westerly wind anomalies emerge over the equatorial Pacific, favoring El Niño development (cf. La Niña for decreased ASO). These results highlight the importance of chemical–radiative–dynamical processes in the Arctic stratosphere for understanding tropospheric climate variability.