06 Sep 2022
06 Sep 2022
Status: this preprint is currently under review for the journal ACP.

Long–term upper–troposphere climatology of potential contrail occurrence over the Paris area derived from radiosonde observations

Kevin Wolf1, Nicolas Bellouin1,2, and Olivier Boucher1 Kevin Wolf et al.
  • 1Institut Pierre–Simon Laplace, Sorbonne Université / CNRS, Paris, France
  • 2Department of Meteorology, University of Reading, Reading, United Kingdom

Abstract. Condensations trails (or contrails) that form behind aircraft have been of climatic interest for many years. Yet their radiative forcing is still uncertain. A number of studies estimate the radiative impact of contrails to be similar or even larger than that of CO2 emitted by aviation. Hence, contrail mitigation may represent a significant opportunity to reduce the overall climate effect of aviation. Here we analyze an 8 year dataset of radiosonde observations from Trappes, France, in terms of the potential for contrail and induced cirrus formation. We focus on the contrail vertical and temporal distribution and test mitigation opportunities by changing flight altitudes and fuel type. Potential contrail formation is identified with the Schmidt–Appleman criterion (SAc). The uncertainty of the SAc, due to variations in aircraft type and age, is estimated by a sensitivity study and is found to be larger than the radiosonde measurement uncertainties. Linkages between potential contrail formation layers and the thermal tropopause as well as with the altitude of the jet stream maximum are determined. While non-persistent contrails form at the tropopause level and around 1.5 km above the jet stream, persistent contrails are located approximately 1.5 km below the thermal tropopause and at the altitude of the jet stream. The correlation between contrail formation layers and the thermal tropopause and jet stream maximum allows to use these quantities as proxies to identify potential contrail formation in numerical weather prediction models. The contrail mitigation potential is tested by varying today's flight altitude distribution. It is found that flying 0.8 km higher during winter and lowering flight altitude in summer reduces the probability for contrail formation. Furthermore, the effect of prospective jet engine developments and their influence on contrail formation are tested. An increase in propulsion efficiency leads to a general increase in the potential occurrence of non-persistent and persistent contrails. Finally, the impact of alternative fuels (ethanol, methane, and hydrogen) is estimated and found to generally increase the likelihood of non-persistent contrails and to a more limited extent persistent contrails.

Kevin Wolf et al.

Status: open (until 18 Oct 2022)

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Kevin Wolf et al.


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Short summary
Recent studies estimate the radiative impact of contrails to be similar or larger than that of emitted CO2. Hence, contrail mitigation might be an opportunity to reduce the climate effect of aviation. A radiosonde data-set is analyzed in terms of the vertical distribution of potential contrails, contrail mitigation by flight altitude changes, and linkages with the tropopause and the jet stream. The effect of prospective jet engine developments and alternative fuels is estimated.