Articles | Volume 26, issue 4
https://doi.org/10.5194/acp-26-3145-2026
© Author(s) 2026. 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-26-3145-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
03 Mar 2026
Research article |
| 03 Mar 2026
| 03 Mar 2026
Contrail formation for aircraft with hydrogen combustion – Part 2: Engine-related aspects
Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
Simon Unterstrasser
Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
Related authors
Josef Zink, Simon Unterstrasser, and Ulrike Burkhardt
Atmos. Chem. Phys., 26, 3125–3143, https://doi.org/10.5194/acp-26-3125-2026, https://doi.org/10.5194/acp-26-3125-2026, 2026
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The climate impact of aviation-induced contrail cirrus is strongly influenced by the number of ice crystals that form in an aircraft's exhaust plume. In this study, we systematically investigate the key microphysical processes of contrail formation for hydrogen combustion. A large simulation data set provides the basis for a data-driven parameterization of ice crystal number that can be integrated into large-scale models.
Andreas Bier, Simon Unterstrasser, Josef Zink, Dennis Hillenbrand, Tina Jurkat-Witschas, and Annemarie Lottermoser
Atmos. Chem. Phys., 24, 2319–2344, https://doi.org/10.5194/acp-24-2319-2024, https://doi.org/10.5194/acp-24-2319-2024, 2024
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Using hydrogen as aviation fuel affects contrails' climate impact. We study contrail formation behind aircraft with H2 combustion. Due to the absence of soot emissions, contrail ice crystals are assumed to form only on ambient particles mixed into the plume. The ice crystal number, which strongly varies with temperature and aerosol number density, is decreased by more than 80 %–90 % compared to kerosene contrails. However H2 contrails can form at lower altitudes due to higher H2O emissions.
Josef Zink, Simon Unterstrasser, and Ulrike Burkhardt
Atmos. Chem. Phys., 26, 3125–3143, https://doi.org/10.5194/acp-26-3125-2026, https://doi.org/10.5194/acp-26-3125-2026, 2026
Short summary
Short summary
The climate impact of aviation-induced contrail cirrus is strongly influenced by the number of ice crystals that form in an aircraft's exhaust plume. In this study, we systematically investigate the key microphysical processes of contrail formation for hydrogen combustion. A large simulation data set provides the basis for a data-driven parameterization of ice crystal number that can be integrated into large-scale models.
Vanessa Santos Gabriel, Luca Bugliaro, Mara Montag, Sabrina Ries, Ziming Wang, Kai Widmaier, Matteo Arico, Simon Unterstrasser, Johanna Mayer, Deniz Menekay, Andreas Marsing, Elena de la Torre Castro, Liam Megill, Monika Scheibe, and Christiane Voigt
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2025-740, https://doi.org/10.5194/essd-2025-740, 2026
Preprint under review for ESSD
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We provide observations of the geostationary Meteosat satellite with contrails labeled by three people complemented with detailed cloud information. Contrails influence climate but are hard to identify in satellite imagery. With this study, we support contrail detection development and evaluation, stress the subjectivity of human labeling and reveal which meteorological conditions highlight or hide contrails. This dataset contributes to a better understanding of aviation’s climate impact.
Gregor Neumann, Andreas Marsing, Theresa Harlass, Daniel Sauer, Simon Braun, Magdalena Pühl, Christopher Heckl, Paul Stock, Elena De La Torre Castro, Valerian Hahn, Anke Roiger, Christiane Voigt, Simon Unterstraßer, Jean Cammas, Charles Renard, Roberta Vasenden, Arnold Vasenden, and Tina Jurkat-Witschas
Atmos. Meas. Tech., 18, 6795–6816, https://doi.org/10.5194/amt-18-6795-2025, https://doi.org/10.5194/amt-18-6795-2025, 2025
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This study presents the first successful in-flight emission characterization of a turboprop engine using a fully autonomous airborne measurement platform, offering new insights into the atmospheric impacts of regional aviation. By equipping the high-altitude Grob G 520 Egrett with a suite of custom and modified commercial instruments, we demonstrate precise, high-resolution measurements of aerosol particles, trace gases, and contrail ice in the engine exhaust plume at cruise altitudes.
Hannes Bruder, Robin Niclas Thor, Malte Niklaß, Katrin Dahlmann, Roland Eichinger, Florian Linke, Volker Grewe, Simon Unterstrasser, and Sigrun Matthes
EGUsphere, https://doi.org/10.5194/egusphere-2025-4700, https://doi.org/10.5194/egusphere-2025-4700, 2025
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We develop an easy-to-use tool to estimate the per-flight climate effect of CO2 and non-CO2 emissions, based only on aircraft size as well as origin and destination airports. The implemented model results from a comparison of Multiple and Symbolic Regression approaches and exhibits a mean relative error of 21 % with respect to climate response model results. The simplified method is designed for climate footprint assessment and covers jet-powered passenger aircraft with over 20 seats.
Annemarie Lottermoser and Simon Unterstrasser
Atmos. Chem. Phys., 25, 7903–7924, https://doi.org/10.5194/acp-25-7903-2025, https://doi.org/10.5194/acp-25-7903-2025, 2025
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Contrail cirrus significantly contributes to aviation's overall climate impact. As hydrogen combustion and fuel cell use are emerging technologies for aircraft propulsion, we simulated individual contrails from hydrogen propulsion during the first 6 min after exhaust emission, termed the vortex phase. The ice crystal loss during that stage is crucial, as the number of ice crystals has a large impact on the further evolution of contrails into contrail cirrus and their radiative forcing.
Andreas Bier, Simon Unterstrasser, Josef Zink, Dennis Hillenbrand, Tina Jurkat-Witschas, and Annemarie Lottermoser
Atmos. Chem. Phys., 24, 2319–2344, https://doi.org/10.5194/acp-24-2319-2024, https://doi.org/10.5194/acp-24-2319-2024, 2024
Short summary
Short summary
Using hydrogen as aviation fuel affects contrails' climate impact. We study contrail formation behind aircraft with H2 combustion. Due to the absence of soot emissions, contrail ice crystals are assumed to form only on ambient particles mixed into the plume. The ice crystal number, which strongly varies with temperature and aerosol number density, is decreased by more than 80 %–90 % compared to kerosene contrails. However H2 contrails can form at lower altitudes due to higher H2O emissions.
Michael A. Olesik, Jakub Banaśkiewicz, Piotr Bartman, Manuel Baumgartner, Simon Unterstrasser, and Sylwester Arabas
Geosci. Model Dev., 15, 3879–3899, https://doi.org/10.5194/gmd-15-3879-2022, https://doi.org/10.5194/gmd-15-3879-2022, 2022
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In systems such as atmospheric clouds, droplets undergo growth through condensation of vapor. The broadness of the resultant size spectrum of droplets influences precipitation likelihood and the radiative properties of clouds. One of the inherent limitations of simulations of the problem is the so-called numerical diffusion causing overestimation of the spectrum width, hence the term numerical broadening. In the paper, we take a closer look at one of the algorithms used in this context: MPDATA.
Andreas Bier, Simon Unterstrasser, and Xavier Vancassel
Atmos. Chem. Phys., 22, 823–845, https://doi.org/10.5194/acp-22-823-2022, https://doi.org/10.5194/acp-22-823-2022, 2022
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We investigate contrail formation in an aircraft plume with a particle-based multi-trajectory 0D model. Due to the high plume heterogeneity, contrail ice crystals form first near the plume edge and then in the plume centre. The number of ice crystals varies strongly with ambient conditions and soot properties near the contrail formation threshold. Our results imply that the multi-trajectory approach does not necessarily lead to improved scientific results compared to a single mean trajectory.
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Short summary
The climate impact of aviation-induced contrail cirrus clouds is strongly influenced by the number of ice crystals that form in the wake of an aircraft under certain conditions. In this study, we investigate how engine-related aspects influence the number of ice crystals formed for hydrogen combustion. We derive suitable (scaling) relations that can be integrated into large-scale models used to estimate the climate impact of contrail cirrus clouds.
The climate impact of aviation-induced contrail cirrus clouds is strongly influenced by the...
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