Evidence for energetic particle precipitation and quasi-biennial oscillation modulations of the Antarctic NO 2 springtime stratospheric column from OMI observations

Gordon, Emily M.; Seppälä, Annika; Tamminen, Johanna

Observations from the Ozone Monitoring Instrument (OMI) on the Aura satellite are used to study the effect of energetic particle precipitation (EPP, as proxied by the geomagnetic activity index, inline-formulaAp) on the Antarctic stratospheric inline-formulaNO2 column in late winter–spring (August–December) during the period from 2005 to 2017. We show that the polar (60–90inline-formula S) stratospheric inline-formulaNO2 column is significantly correlated with EPP throughout the Antarctic spring, until the breakdown of the polar vortex in November. The strongest correlation takes place during years with the easterly phase of the quasi-biennial oscillation (QBO). The QBO modulation may be a combination of different effects: the QBO is known to influence the amount of the primary inline-formulaNOx source (inline-formulaN2O) via transport from the Equator to the polar region; and the QBO phase also affects polar temperatures, which may provide a link to the amount of denitrification occurring in the polar vortex. We find some support for the latter in an analysis of temperature and inline-formulaHNO3 observations from the Microwave Limb Sounder (MLS, on Aura). Our results suggest that once the background effect of the QBO is accounted for, the inline-formulaNOx produced by EPP significantly contributes to the stratospheric inline-formulaNO2 column at the time and altitudes when the ozone hole is present in the Antarctic stratosphere. Based on our findings, and the known role of inline-formulaNOx as a catalyst for ozone loss, we propose that as chlorine activation continues to decrease in the Antarctic stratosphere, the total EPP-inline-formulaNOx needs be accounted for in predictions of Antarctic ozone recovery.

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Gordon, Emily M. / Seppälä, Annika / Tamminen, Johanna: Evidence for energetic particle precipitation and quasi-biennial oscillation modulations of the Antarctic NO2 springtime stratospheric column from OMI observations. 2020. Copernicus Publications.

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