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

该项目的目标是增进我们对温带气旋和极地急流区域温带对流层顶混合和输送的详细了解。为此，我们将使用一个新开发的模式系统，该系统将区域模式的分辨率与仅在全球模式中提供的动力和化学设置一致地结合在一起。温带对流层顶区的输送和混合对于理解臭氧和水蒸气起着关键作用，而臭氧和水蒸气影响大气的辐射收支。全球化学气候模式(CCM)可以模拟对流层顶区的整体结构，但不能模拟详细的过程。卫星和现场观测表明，在温带对流层顶的混合导致了混合层的形成。这一层可以用所谓的混合线来表征，这表明不可逆的跨对流层顶交换。对于导致混合线形成的潜在动力过程的空间和时间尺度，人们知之甚少。极地急流和温带气旋对温带对流层顶区的组成以及混合线的形成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层和远距离输送。在其发展的侵蚀阶段，复杂的动力过程决定了对流层和对流层顶区域内输送物质的混合和命运。新开发的模式系统MECO(N)将中尺度大气化学模式与全球大气化学模式相结合。该系统特别允许在MECO(N)内以不同分辨率一致地模拟动力和化学过程。因此，有可能以高分辨率研究动力和化学过程的时间和空间尺度，并量化与低分辨率全球模式的差异。

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.