Gravity Waves and Trace Gas Mixing in the Arctic Winter Tropopause Region
Final Report Abstract
Within this project the effect of orographic waves and jet induced shear on the generation of turbulence and tracer mixing was studied. Based on the measured distribution of highly resolved N2O and CO as well as the vertical wind and potential temperatures strong perturbations of isentropic layers over a mountain ridge over New Zealand could be identified. Tracer correlation reveals a strong impact of mixing in the region of the mountains pertaining into the leeward side, leading to different vertical slopes compared to the upwind side of the mountain ridge. Detailed slope analysis of the N2O gradient relative to potential temperature showed changes above the mountain therefore indicating cross isentropic exchange of N 2O across the tropopause. Fluxes where on the order of 0.5 ppbv m/s for the case induced by horizontal wave lengths of 6-16 km. In a similar case on the northern hemisphere turbulence and mixing induced by vertical shear of the horizontal wind could be identified and directly linked to perturbations and tracer-tracer correlations indicative for mixing and irreversible tracer exchange at the tropopause. This is the first time, that the tracer-tracer correlation diagnostics could be directly linked to physical local process, generating turbulence. In the first case orographic waves generated the turbulence regime, whereas for the second case shear induced instability could be identified to drive the turbulent mixing.
Publications
- Observed versus simulated mountain waves over Scandinavia – improvement of vertical winds, energy and momentum fluxes by enhanced model resolution?, Atmos. Chem. Phys., 17, 4031–4052, 2017
Wagner, J., Dörnbrack, A., Rapp, M., Gisinger, S., Ehard, B., Bramberger, M., Witschas, B., Chouza, F., Rahm, S., Mallaun, C., Baumgarten, G., and Hoor, P.
(See online at https://doi.org/10.5194/acp-17-4031-2017) - Mixing and ageing in the polar lower stratosphere in winter 2015–2016, Atmos. Chem. Phys., 18, 6057–6073, , 2018
Krause, J., Hoor, P., Engel, A., Plöger, F., Grooß, J.-U., Bönisch, H., Keber, T., Sinnhuber, B.-M., Woiwode, W., and Oelhaf, H.
(See online at https://doi.org/10.5194/acp-18-6057-2018)
