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Research Area C - TPChange TRR 301 - Wolken
TPChange 5 Projects 5 Research Area C 5 Project C02

Project C02:
Deriving transport timescales in the UTLS from age tracers and the propagation of the seasonal cycle of CO2

Brief Summary

In this project we propose to perform regular observations of CO2, CH4 and CO using the AirCore technique which has been established in recent years at University Frankfurt and further developed especially with respect to the altitude attribution. The CO2, CH4 and CO profiles derived from the Air-Core observations will be used to investigate how the seasonality of CO2 in the troposphere propagates into the lowermost stratosphere. For this we will combine these observations, which can reach altitudes up to about 27 km, with more extensive measurements available further down in the UTLS, e.g. from research aircraft andfrom regular airborne sampling programmes. It is expected that the propagation of this signal is largely modulated by the strength of the subtropical jet, which is weakest during summer, which should result in stronger exchange. While fluxes across the extratropical tropopause cannot be measured directly, the shift in the seasonal cycle is expected to be a good indicator of when the exchange is strong and also of how far into the lowermost stratosphere this occurs during which season.
The first central research question is how the strength of the coupling between the tropics and extratropics in the UTLS is modulated by the strength of the sub-tropical jet. This investigation is based on the propagation of the seasonal cycle of CO2. Here we suggest to use our observations in combination with models to see how well this process is represented in models. This investigation will use special tracers in the model, in particular a CO2-like tracer which has a similar seasonal cycle but no ling term trend. The second central research question is the strength of the overturning stratospheric circulation, the so-called Brewer-Dobson circulation, and its variation different geographical and temporal scales. For this analyses we will focus on the seasonality and latitudinal (using equivalent latitude) variability of mean age values in the lower and middle stratosphere. This informationcan be used to allow a better constraint on variabilities of mean age derived from the observations dating back to 1976.


Prof. Dr. Andreas Engel - TPChange

Prof. Dr. Andreas Engel

Principal Investigator

Goethe-Universität Frankfurt, Institut für Atmosphäre und Umwelt


Prof. Dr. Peter Hoor - Speaker of TRR 301 TPChange

Prof. Dr. Peter Hoor

Principal Investigator

Johannes Gutenberg-Universität Mainz, Institut für Physik der Atmosphäre



Timo Keber


Goethe-Universität Frankfurt, Institut für Atmosphäre und Umwelt


Johannes Degen

Johannes Degen

Associated Doctoral Candidate

Goethe-Universität Frankfurt, Institut für Atmosphäre und Umwelt



Wagenhäuser, T., M. Jesswein, T. Keber, T. Schuck, and A. Engel (2023): Mean age from observations in the lowermost stratosphere: an improved method and interhemispheric differences. Atmospheric Chemistry and Physics 23 (7), 3887–3903. doi: