What Do We Need To Do To Improve Our Understanding of How Volcanoes Affect Stratospheric Ozone?

Abstract:

This talk will briefly survey what is known and what is not known about stratospheric ozone depletion and volcanic events, and will describe some ways to improve our understanding. Observations of total ozone following the eruption of El Chichon in the 1980s provided some of the earliest and clearest indications of the importance of volcanic aerosol on ozone depletion. In subsequent decades, improved laboratory information, modeling studies, and observations showed how heterogeneous chemical processing on and in volcanic aerosols could enhance chlorine-catalyzed ozone loss in the lower stratosphere, while decreasing nitrogen-catalyzed ozone loss in the upper stratosphere. Recent satellite observations shed important light on this chemistry but major gaps in understanding remain, including for example a lack of knowledge of whether hydrochloric acid can be efficiently taken up in stratospheric particles under cold conditions, interactions and competition between volcanic aerosols and ice clouds, and the effects of volcanic aerosols on chemistry in the tropopause region. Effects of volcanic aerosols on Arctic and Antarctic ozone depletion are also subject to many certainties, owing in large part to observational deficiencies. Implications for gaining an improved understanding through both laboratory studies and new observations will be briefly described.