3D Chemical Lifetimes in the Middle Atmosphere (CLiMAte3D)

• Applicant: Professorin Dr. Claudia Christine Stephan
• Subject Area: Atmospheric Science
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 547675919

The chemical characteristic time (CCT) is the time during which the concentration of a given constituent changes by a factor e. The concept of characteristic times is widely used: • to understand which factors – advection, turbulence or chemistry – are important for changes in a given chemical compound in a given region at a given time • to identify which sources of atmospheric variability, e.g. planetary waves (PWs), gravity waves (GWs), tides, result in variations of a given chemical compound • to assess the degree to which chemical constituents are in their equilibrium, which is often an important assumption • to construct climate change scenarios. Despite all these applications of the characteristic time concept, there are a number of unsolved problems: • the reciprocal loss term is widely used to assess CCT, but it does not include production, which is rather important for atmospheric chemistry • until now the CCT has only been investigated for 1D and 2D cases • studies focused on midnight and noon, but CCTs of a large number of chemical constituents have a diurnal cycle • similarly, studies focused on equinox and solstice, but CCTs have an annual cycle • the effects of GWs and PWs are unknown • there is no information about CCT dependence on the 11-year solar cycle. We propose a comprehensive global investigation of CCT based on 3D time-dependent modelling. The comparison with characteristic advective and diffusive transport times renders the results directly applicable to analyses of satellite, rocket-born, and ground-based observations. We intend to study both traditional and so-called effective CCT, which includes production, specifically:• 3D annual distributions and diurnal variations of CCT • impacts of PWs • nonlinear effects of dynamics on chemistry • influence of the 11-year Lyman-α solar cycle. This research is critical for a reliable interpretation of measurements, numerical simulations and construction of climate change scenarios.

• DFG Programme: Research Grants
• International Connection: Canada
• Co-Investigator: Dr. Mykhaylo Grygalashvyly
• Cooperation Partner: Professor Dr. William E. Ward