Stratospheric and Tropospheric Ozone over Alps and Europe

Ozone in the atmosphere is a strong absorber of solar ultraviolet radiation, thereby acting as a shield to protect humans and Earth`s biosphere from this harmful radiation. Manmade chemicals containing halogen compounds released into the atmosphere since the middle of the last century are responsible for the observed depletion of ozone in the stratosphere, the atmospheric layer where most of the ozone is located. The Montreal Protocol and its amendments have led to decreases in the atmospheric abundance of those controlled ozone- depleting substances, however, no significant trend in total column ozone (TOC) has been detected at mid-latitudes so far. The absence of a significant recovery signal is also due to differences in ozone drivers across atmospheric layers. This project will quantify trends in TOC and in atmospheric ozone layers ranging from the troposphere to the upper stratosphere since the 1990s using a comprehensive dataset of ozone measurements from different ozone measuring platforms across Europe, including the Worlds longest continuous TOC dataset from Arosa/Davos and the TOC dataset from Hoher Sonnblick. As observation based approaches alone do not suffice to cleanly seperate trends across atmospheric layers, chemistry-climate and chemistry-transport model simulations will complement the observational analyses and allow to quantify the atmospheric dynamics and chemistry contributions to the observed ozone changes. Thereby the project will provide a deep understanding of the past and expected future ozone evolution over the Alps and Europe and its underlying drivers. The project will also provide a quantification of the contributions of changes in the troposphere and stratosphere to net total column changes, as well as an indepth evaluation of the uncertainties in the existing observational timeseries and measurement techniques.