EPP-NOx in Antarctic springtime stratospheric column: Evidence from observations and influence of the QBO

• Main Authors: Gordon, Emily, Seppälä, Annika, Tamminen, Johanna
• Format: Text
• Language: English
• Published: 2019
• Subjects: Antarctic; The Antarctic; Antarc*
• Online Access: https://doi.org/10.5194/acp-2019-1035; https://www.atmos-chem-phys-discuss.net/acp-2019-1035/

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 A p ) on the Antarctic stratospheric NO 2 column in late winter-spring (Aug-Dec) during the years 2005–2017. We show that the polar (60° S–90° S) stratospheric NO 2 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 easterly phase of the quasi-biennial oscillation (QBO). We propose that the QBO affects the polar springtime EPP-NO x in two ways: firstly by modulating the amount of the primary NO x source, N 2 O, transported to the polar region. Secondly, the QBO affects the temperature of the polar vortex and thus the amount of denitrification occurring in the polar vortex, also verified from HNO 3 observations from the Microwave Limb Sounder (MLS/Aura). Our results suggest that NO x produced by EPP significantly contributes to the stratospheric NO 2 column at the time when the ozone hole is present in the Antarctic stratosphere. Based on our findings, we recommend that as chlorine activation continues to decrease in the Antarctic stratosphere, the total EPP-NO x should be accounted for in predictions of Antarctic ozone recovery.