Trace gas transport on global and regional scales in the light of a new model system: mixing and mixing lines at the polar front

• Applicant: Professor Dr. Peter Hoor
• Subject Area: Atmospheric Science
• Term: from 2012 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 227719076

The goal of this project is to improve our detailed understanding of mixing and transport at the extratropical tropopause in the region of extratropical cyclones and the polar jet. For this purpose we will use a newly developed model system, which consistently combines the resolution of a regional model with the dynamical and chemical setup only available in a global model. Transport and mixing in the extratropical tropopause region play a key role for the understanding of ozone and water vapour, which affect the radiation budget of the atmosphere. Global Chemistry Climate Models (CCM's) allow to simulate the overall structure of the tropopause region, but are not able to simulate the detailed processes. Satellite and in-situ observations indicate that mixing at the extratropical tropopause lead to the formation of a mixing layer. This layer can be characterized by so-called mixing lines, which indicate irreversible cross tropopause exchange. The spatial and temporal scales of the underlying dynamical processes, which lead to the formation of mixing lines are only poorly understood. For the composition of the extratropical tropopause region and therefore the formation of mixing lines the polar jet as well as extratropical cyclones play a crucial role. The latter allow a rapid vertical transport of substances into the upper troposphere and long range transport. In the eroding stage of their development complex dynamical processes determine mixing and the fate of the transported substances within the troposphere as well as in the tropopause region. The newly developed model system MECO(n) couples a mesoscale atmospheric chemistry model with a global atmospheric chemistry model. The system allows in particular the consistent simulation of the dynamical and chemical processes in different resolutions within MECO(n). Therefore it is possible to investigate temporal and spatial scales of the dynamical and chemical processes with high resolution and quantify the differences to the lower resolution global model.

• DFG Programme: Research Grants
• Participating Person: Dr. Astrid Kerkweg