Reactive nitrogen (NO<sub><i>y</i></sub>) and ozone responses to energetic electron precipitation during Southern Hemisphere winter

Abstract

<p><strong>Abstract.</strong> Energetic particle precipitation (EPP) affects the chemistry of the polar middle atmosphere by producing reactive nitrogen (NO<sub><i>y</i></sub>) and hydrogen (HO<sub><i>x</i></sub>) species, which then catalytically destroy ozone. Recently, there have been major advances in constraining these particle impacts through a parametrization based on high quality observations. Here we investigate the effects of low (auroral) and middle (radiation belt) energy range electrons, separately and in combination, on reactive nitrogen and hydrogen species as well as on ozone during Southern Hemisphere winters from 2002 to 2010 using the chemistry-climate model SOCOL3-MPIOM. Our results show that, in absence of solar proton events, low energy electrons produce the majority of NO<sub><i>y</i></sub> in the polar mesosphere and stratosphere. In the polar vortex, NO<sub><i>y</i></sub> subsides and affects ozone at lower altitudes, down to 10 hPa. Comparing a year with high electron precipitation with a quiescent period, we found large ozone depletion in the mesosphere; as the anomaly propagates downward, 15 % less ozone is found in the stratosphere during winter, which is confirmed by satellite observations. Only with both low and middle energy electrons, our model reproduces the observed stratospheric ozone anomaly.</p>

Role Of the Sun and the Middle atmosphere/thermosphere/ionosphere In Climate (ROSMIC): a retrospective and prospective view

“…This is slightly more than found by Fytterer et al (2015), who estimated Antarctic ozone depletion of 5-10% using observations from a different set of satellite instruments. Using two independent chemistry-climate models (CCMs), Arsenovic et al (2019) and Pettit et al (2019) showed that only by including EEP were models able to reproduce stratospheric ozone anomalies found in satellite observations. A number of further studies (e.g., Zawedde et al (2016) Together, these suggest that there is need to improve the EEP forcing (the current EEP proxies are known to underestimate precipitating levels, see Nesse Tyssøy et al (2019)) to ensure better representation of ozone variability in the middle atmosphere.…”