Observational evidence of energetic particle precipitation NO<sub><i>x</i></sub> (EPP-NO<sub><i>x</i></sub>) interaction with chlorine curbing Antarctic ozone loss

Abstract. We investigate the impact of so-called energetic particle precipitation (EPP) indirect effect on lower stratospheric ozone, ClO, and ClONO2 in Antarctic springtime. use observations from Microwave Limb Sounder (MLS) Ozone Monitoring Instrument (OMI) Aura, Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS) SCISAT, Michelson Interferometer for Passive Sounding (MIPAS) Envisat, covering period 2005 to 2017. Using geomagnetic activity index Ap as a proxy EPP, we find consistent ozone increases with elevated EPP during years an easterly phase quasi-biennial oscillation (QBO) both OMI MLS observations. While these are opposite what has previously been reported at higher altitudes, pattern O3 follows typical descent patterns EPP-NOx. The enhancements also present total column Analogous found O3, decreases springtime ClO following winters EPP. To verify if this is due proposed mechanism involving conversion reservoir species reaction NO2, used ACE-FTS MIPAS. As NO2 catalysts destruction, would result increase. positive correlation between upper stratosphere early spring late spring, providing first observational evidence supporting relating EPP-NOx modulating Clx-driven loss. Our findings suggest that played important role depletion last 15 years. chlorine loading polar continues decrease future, buffering will become less effective, catalytic destruction by likely major contributor