Towards a quantification of vortex impact on the arctic lowermost stratosphere

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The lowermost stratosphere of the polar regions is charecterized by diabatic downwelling from the vortex, downward transport in mid latitude stratosphere and mixing from low latitudes as part of the lower branch of the Brewer-Dobson circulation. In lower altitude mixing across the extratropical tropopause additionally contributes leading to the formation of the extratropical transition layer (ExTL). In the northern hemisphere a considerable variability due to the intraannual variability of the dynamical conditions leads to a high interannual variability of the arctic LMS composition. In this proposal we want to quantify the contribution of the main reservoirs. We will do this on the basis of fast (1-3Hz) airborne measurements of different tracers. We will use the newly added species ethane (C2H6) as an indicator for aged vortex air. Combined with N2O, CO we set up a budget to infer the relative contributions from the relevant source regions of air to qunatify the impact of vortex air on the lowermost stratosphere. We will further determine the impact of the tropospheric fraction constituting the ExTL and compare the vertical extent of the ExTL for different years (winter 2015/2016) and the southern hemisphere (SOUTHTRAC) to infer information about the variability of the ExTL depths under different dynamical conditions. Finally we will study the interaction of former vortex filaments with the lowermost stratospheric background. We will specifically focus on filaments subject to strong shear or passing regions of gravity wave activity, which both my lead to dynamical instability and turbulence. We will study mixing between these filaments and the surrounding air and infer tracer fluxes for such events.