Publication

Journal	ATMOSPHERIC CHEMISTRY AND PHYSICS
Volume (Issue)	15(20)
Page(s)	11461 - 11476
Title of proceedings	ATMOSPHERIC CHEMISTRY AND PHYSICS
DOI	10.5194/acp-15-11461-2015

URL	http://www.atmos-chem-phys.net/15/11461/2015/
Type of Open Access	Website

After major volcanic eruptions the enhanced aerosol causes ozone changes due to greater heterogeneous chemistry on the particle surfaces (HET-AER) and from dy- namical effects related to the radiative heating of the lower stratosphere (RAD-DYN). We carry out a series of experi- ments with an atmosphere–ocean–chemistry–climate model to assess how these two processes change stratospheric ozone and Northern Hemispheric (NH) polar vortex dynamics. En- semble simulations are performed under present day and preindustrial conditions, and with aerosol forcings represen- tative of different eruption strength, to investigate changes in the response behaviour. We show that the halogen com- ponent of the HET-AER effect dominates under present-day conditions with a global reduction of ozone (−21DU for the strongest eruption) particularly at high latitudes, whereas the HET-AER effect increases stratospheric ozone due to N2O5 hydrolysis in a preindustrial atmosphere (maximum anomalies +4 DU). The halogen-induced ozone changes in the present-day atmosphere offset part of the strengthening of the NH polar vortex during mid-winter (reduction of up to −16 m s−1 in January) and slightly amplify the dynamical changes in the polar stratosphere in late winter (+11ms−1 in March). The RAD-DYN mechanism leads to positive col- umn ozone anomalies which are reduced in a present-day atmosphere by amplified polar ozone depletion (maximum anomalies +12 and +18 DU for present day and preindustrial, respectively). For preindustrial conditions, the ozone re- sponse is consequently dominated by RAD-DYN processes, while under present-day conditions, HET-AER effects dom- inate. The dynamical response of the stratosphere is domi- nated by the RAD-DYN mechanism showing an intensifica- tion of the NH polar vortex in winter (up to +10ms−1 in January). Ozone changes due to the RAD-DYN mechanism slightly reduce the response of the polar vortex after the erup- tion under present-day conditions.