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

这个项目的目标是提高我们对对流层顶外气旋和极地急流区域的混合和输送的详细了解。为此，我们将使用一个新开发的模型系统，该系统始终结合了区域模型的分辨率与全球模型中仅提供的动力学和化学设置。对流层顶外区域的输送和混合对于理解臭氧和水蒸气起着关键作用，臭氧和水蒸气影响着大气的辐射收支。全球化学气候模式（CCM）允许模拟对流层顶区域的整体结构，但不能模拟详细的过程。卫星和现场观测表明，在对流层顶的混合导致混合层的形成。这一层可以用所谓的混合线来表征，这表明不可逆的对流层顶交换。导致混合线形成的基本动力学过程的空间和时间尺度知之甚少。对于对流层顶外区域的组成和混合线的形成，极急流和对流层外气旋起着至关重要的作用。后者允许物质快速垂直输送到对流层上部和远距离输送。在其发展的侵蚀阶段，复杂的动力学过程决定了对流层和对流层顶区域内被输送物质的混合和命运。新开发的模式系统MECO（n）耦合了中尺度大气化学模式和全球大气化学模式。该系统特别允许在MECO（n）内以不同分辨率对动力学和化学过程进行一致的模拟。因此，它是可能的调查时间和空间尺度的动力学和化学过程的高分辨率和量化的差异，以较低的分辨率全球模式。

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.