Articles | Volume 20, issue 21
Atmos. Chem. Phys., 20, 12391–12408, 2020
Atmos. Chem. Phys., 20, 12391–12408, 2020

Research article 30 Oct 2020

Research article | 30 Oct 2020

Gravitational separation of Ar∕N2 and age of air in the lowermost stratosphere in airborne observations and a chemical transport model

Benjamin Birner et al.

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Cited articles

Andrews, A. E., Boering, K. A., Daube, B. C., Wofsy, S. C., Hintsa, E. J., Weinstock, E. M., and Bui, T. P.: Empirical age spectra for the lower tropical stratosphere from in situ observations of CO2: Implications for stratospheric transport, J. Geophys. Res., 104, 26581–26595,, 1999. 
Andrews, A. E., Boering, K. A., Wofsy, S. C., Daube, B. C., Jones, D. B., Alex, S., Loewenstein, M., Podolske, J. R., and Strahan, S. E.: Empirical age spectra for the midlatitude lower stratosphere from in situ observations of CO2: Quantitative evidence for a subtropical “barrier” to horizontal transport, J. Geophys. Res., 106, 10257–10274,, 2001. 
Baggenstos, D., Häberli, M., Schmitt, J., Shackleton, S. A., Birner, B., Severinghaus, J. P., Kellerhals, T., and Fischer, H.: Earth's radiative imbalance from the Last Glacial Maximum to the present, P. Natl. Acad. Sci. USA, 116, 14881–14886,, 2019. 
Banks, P. M. and Kockarts, G.: Aeronomy, Part B, 1st edn., Academic Press, New York, USA and London, UK, 1973. 
Short summary
With new high-precision observations from nine aircraft campaigns and 3-D chemical transport modeling, we show that the argon-to-nitrogen ratio (Ar / N2) in the lowermost stratosphere provides a useful constraint on the “age of air” (the time elapsed since entry of an air parcel into the stratosphere). Therefore, Ar / N2 in combination with traditional age-of-air indicators, such as CO2 and N2O, could provide new insights into atmospheric mixing and transport.
Final-revised paper