Articles | Volume 24, issue 13
https://doi.org/10.5194/acp-24-7911-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-24-7911-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
11 Jul 2024
Research article |
| 11 Jul 2024
| 11 Jul 2024
How well can persistent contrails be predicted? An update
Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen, Germany
Klaus Gierens
Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen, Germany
Susanne Rohs
Forschungszentrum Jülich, IEK-8, Jülich, Germany
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The climate effect of contrails depends on the contrail lifetime. Thus, it is important to know what constrains the lifetime. In this paper, we characterise the two most important contrail dissolution processes via their respective timescales. Both timescales are in the order of a couple of hours, depending on the synoptic situation and the size of the contrail ice crystals. The combined timescale, which combines both processes, is the harmonic mean of the two single timescales.
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Ice supersaturation is an immaterial feature that does not generally move with the wind that carries contrails and cirrus clouds. Here we analyse the different motions and show that ice supersaturated regions (ISSRs) on average move slower than the wind, the direction of movement is usually quite similar, and the distributions of both velocities follow Weibull distributions. The almost identical direction of the movements is beneficial for contrail lifetimes.
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ERA5 atmospheric reanalysis and airborne in situ observations from IAGOS are compared in terms of the representation of the contrail formation potential and the presence of supersaturation. Differences are traced back to biases in ERA5 relative humidity fields. Those biases are addressed by applying a quantile mapping technique that significantly improved contrail estimation based on post-processed ERA5 data.
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The radiative effect of aviation-induced cirrus is closely related to ambient conditions and its microphysical properties. Our study investigated the occurrence of contrail and natural cirrus measured above central Europe in spring 2014. It finds that contrail cirrus appears frequently in the pressure range 200 to 245 hPa and occurs more often in slightly ice-subsaturated environments than expected. Avoiding slightly ice-subsaturated regions by aviation might help mitigate contrail cirrus.
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We are interested in the prediction of condensation trails, in particular strong ones. For this we need a good forecast of temperature and humidity in the levels where aircraft cruise. Unfortunately, the humidity forecast is quite difficult for these levels, in particular the ice supersaturation, which is needed for long-lasting contrails. We are thus seeking proxy variables that help distinguish situations where strong contrails can form, for instance the lapse rate.
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The African intertropical troposphere is one of the world areas where the increase in ozone mixing ratio has been most pronounced since 1980 and where high carbon monoxide mixing ratios are found in altitude. In this article, IAGOS aircraft measurements, IASI satellite instrument observations, and SOFT-IO model products are used to explore the seasonal distribution variations and the origin of ozone and carbon monoxide over the African upper troposphere.
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Short summary
We try to improve the forecast of ice supersaturation (ISS) and potential persistent contrails using data on dynamical quantities in addition to temperature and relative humidity in a modern kind of regression model. Although the results are improved, they are not good enough for flight routing. The origin of the problem is the strong overlap of probability densities conditioned on cases with and without ice-supersaturated regions (ISSRs) in the important range of 70–100 %.
We try to improve the forecast of ice supersaturation (ISS) and potential persistent contrails...
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