ThE causes and consequences of exceptioNally strong stRatospherIc ArCtic polar vortices and the associated ozone Holes: from seasonal to long-term impacts (ENRICH)

• Applicants: Professor Dr. Peter Braesicke; Professor Dr. Christoph Jacobi, since 7/2024
• Subject Area: Atmospheric Science
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 516378721

While the ozone hole is a frequently-observed event in the Antarctic, the Northern Hemisphere counterpart has, until recently, never been observed. Two notable exceptions have been the severe Arctic chemical ozone depletion events in the years 2011 and 2020 where regional ozone losses over the Arctic were comparable to those in the Antarctic ozone hole. During both events, the Arctic stratospheric polar vortex was exceptionally strong, cold and long-lasting during winter and spring. As a consequence, the total ozone column over the polar cap was substantially lower in both years. For example, the average total ozone column over the northern polar cap in early spring (February-April 2020) was 340 DU, which is about 30% below the long-term mean from 1979 to 2019. These events are unprecedented for the satellite era (1979/1980 to present); thus, the years 2011 and 2020 had the greatest Arctic ozone losses on record. As events like these have never been observed previously, they deserve particular attention. The ENRICH proposal focuses on causes and consequences of such cold and persistent polar vortices and the associated ozone deficits on the thermodynamics, dynamics, chemistry and transport in the middle atmosphere and the troposphere. ENRICH is a jpint project of Leipzig Institute for Meteorology of Leipzig University and the Institute of Meteorology and Climate Research - Atmospheric Trace Gases and Remote Sensing of the Karlsruhe Institute of Technology. The project is intended for two doctoral students and in particular involves model experiments with the ICON-ART model system. We will employ two configurations of the model: One for ensemble seasonal forecasting and another one for long-term climate simulations. The model simulations will be complemented with analyses of CMIP6 model simulations, ERA5 and MERRA reanalysis data and GPS measurements. The project will enable us to investigate:(1) What is the role of climate change in the formation of the exceptionally strong polar vortex and the associated ozone hole in winter/spring 2011 and 2020 and how can this be analysed by using a global spectrally nudged storyline method? What is the fate of such extreme events under climate change? (2) What would have happened to ENRICH-like events under future climate projections, in the coming decades, if the negotiation and ratification of the Montreal Protocol had not been implemented (World Avoided scenario)? (3) What are the relative contributions of dynamical (balanced (Rossby) mode versus inertia-gravity mode) forcing versus chemical/thermodynamic changes in the formation of the extreme polar vortices in present and future climate? (4) What are the consequences of such extreme stratospheric situations (strong polar vortex and low/depleted ozone in the NH) for tropospheric weather?

• DFG Programme: Research Grants
• Co-Investigator: Dr. Miriam Sinnhuber
• Ehemaliger Antragsteller: Dr. Khalil Karami, until 6/2024