Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2017-104
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
08 Feb 2017
Review status
This discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Mean age of stratospheric air derived from AirCore observations
Andreas Engel1, Harald Bönisch1,a, Markus Ullrich1, Robert Sitals1, Olivier Membrive2, Francois Danis2, and Cyril Crevoisier2 1Institute for Atmospheric and Environmental Science, Goethe University Frankfurt, Frankfurt, Germany
2Laboratoire de Météorologie Dynamique (LMD/IPSL), CNRS, Ecole polytechnique, Université Paris-Saclay, Palaiseau, France
anow at: Karlsruhe Institute of Technology, KIT, Karlsruhe, Germany
Abstract. Mean age of stratospheric air can be derived from observations of sufficiently long lived trace gases with approximately linear trends in the troposphere. Mean age can serve as a tracer to investigate stratospheric transport and long term changes in the strength of the overturning Brewer-Dobson circulation of the stratosphere. For this purpose, a low-cost method is required in order to allow for regular observations up to altitudes of about 30 km. Despite the desired low costs, high precision and accuracy are required in order to allow determination of mean age. We present balloon borne AirCore observations from two mid latitude sites: Timmins in Ontario/Canada and Lindenberg in Germany. During the Timmins campaign five AirCores sampled air in parallel from a large stratospheric balloon and were analysed for CO2, CH4 and partly CO. We show that there is good agreement between the different AirCores (better than 0.1 %) especially when vertical gradients are small. The measurements from Lindenberg were performed using small low-cost balloons and yielded very comparable results. We have used the observations to extend our long term data set of mean age observations at Northern Hemi-sphere mid latitudes. The time series now covers more than 40 years and shows a small, statis-tically not significant positive trend of 0.15 ± 0.18 years/decade. This trend is slightly smaller than the previous estimate of 0.24 ± 0.22 years/decade which was based on observations up to the year 2006. These observations are still in contrast to strong negative trends of mean age as derived from some model calculations.

Citation: Engel, A., Bönisch, H., Ullrich, M., Sitals, R., Membrive, O., Danis, F., and Crevoisier, C.: Mean age of stratospheric air derived from AirCore observations, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-104, in review, 2017.
Andreas Engel et al.
Andreas Engel et al.
Andreas Engel et al.

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Short summary
AirCore is new technique to sample stratospheric air. We present new observations of CO2 and CH4 using AirCore, which are used to derive stratospheric transport time, so called mean age of air. The purpose of using AirCore is to provide a cost-effective tool for deriving mean age. Mean age may serve as proxy to investigate changes in stratospheric circulation. We show that these is no statistically significant trend in our 40 year time series of mean age, which is now extended using AirCore.
AirCore is new technique to sample stratospheric air. We present new observations of CO2 and CH4...
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