Articles | Volume 25, issue 20
https://doi.org/10.5194/acp-25-13563-2025
© Author(s) 2025. 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-25-13563-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
23 Oct 2025
Research article |
| 23 Oct 2025
| 23 Oct 2025
A microphysics guide to cirrus – Part 3: Occurrence patterns of cloud particles
Institute of Climate and Energy Systems (ICE-4), Research Center Jülich, Jülich, Germany
Institute for Physics of the Atmosphere (IPA), Johannes Gutenberg University, Mainz, Germany
Nicole Spelten
Institute of Climate and Energy Systems (ICE-4), Research Center Jülich, Jülich, Germany
Christian Rolf
Institute of Climate and Energy Systems (ICE-4), Research Center Jülich, Jülich, Germany
Reinhold Spang
Institute of Climate and Energy Systems (ICE-4), Research Center Jülich, Jülich, Germany
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Nicolas Emig, Annette Miltenberger, Heiko Bozem, Martina Krämer, Armin Afchine, Daniel Kunkel, Hans-Christoph Lachnitt, Yun Li, Philipp Reutter, Christian Rolf, Nicole Spelten, Holger Tost, and Peter Hoor
EGUsphere, https://doi.org/10.5194/egusphere-2026-4614, https://doi.org/10.5194/egusphere-2026-4614, 2026
This preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).
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In this study we show mixing of ice particles across the extratropical tropopause via turbulence in the jet shear zone based on in situ measurements from the TPEx campaign over the North Sea, combined with Lagrangian model analysis. Trace gas correlations and subsaturated ice particles constrain the timing and mechanism, while backward trajectories indicate suitable turbulent conditions beforehand. This process possibly impacts the water vapour budget of the extratropical lowermost stratosphere.
Georgios Dekoutsidis, Silke Groß, Florian Ewald, Martina Krämer, Christian Rolf, Andreas Schäfler, and Martin Wirth
EGUsphere, https://doi.org/10.5194/egusphere-2026-3788, https://doi.org/10.5194/egusphere-2026-3788, 2026
This preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).
Short summary
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Cirrus clouds interact with radiation, but their exact effects are not well-defined and depend on their properties, formation process and the ambient conditions. We used airborne lidar and radar measurements and models in order to compare cirrus that formed in undisturbed conditions and during Warm Air intrusions (WAI). We found that WAIs cause a change in the formation and their properties. Our findings can improve the representation of cirrus in models and the estimation of their impact.
Kasper Juurikkala, Tomi Raatikainen, Martina Krämer, Christina J. Williamson, and Ari Laaksonen
EGUsphere, https://doi.org/10.5194/egusphere-2026-2427, https://doi.org/10.5194/egusphere-2026-2427, 2026
Short summary
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We use large-eddy simulations constrained by observations to study how mineral dust controls the evolution of cirrus clouds during dust outbreaks. Results show that sustained dusty cirrus forms only under strongly elevated dust concentrations, where ice forms mainly on dust particles. This identifies mineral dust as the key control on cirrus persistence and highlights the need to improve representation of dust-driven ice formation in weather and climate models.
Athulya Saiprakash, Martina Krämer, Christian Rolf, Jérôme Riedi, and Odran Sourdeval
EGUsphere, https://doi.org/10.5194/egusphere-2026-2423, https://doi.org/10.5194/egusphere-2026-2423, 2026
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This second part of the study tested the new method by comparing its results with satellite and aircraft observations and by examining how sensitive it is to key assumptions. The method agreed well with observations in most cases, although clouds formed over mountains remained harder to capture. It also showed which conditions and processes matter most for reconstructing how cirrus form and evolve.
Athulya Saiprakash, Martina Krämer, Christian Rolf, Patrick Konjari, Jérôme Riedi, and Odran Sourdeval
EGUsphere, https://doi.org/10.5194/egusphere-2026-2416, https://doi.org/10.5194/egusphere-2026-2416, 2026
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To better understand how observed high ice clouds, known as cirrus, form and change, satellite images were combined with calculations that reconstruct how the air moved before the clouds formed. Case studies showed that cloud history differs with height, age, and surrounding conditions, and that small temperature changes strongly shape cloud growth. This helps reveal and characterize the mechanisms behind observed cirrus.
Rolf Müller, Bärbel Vogel, Martina Krämer, Christian Rolf, Nicole Spelten, and Fabrizio Ravegnani
Atmos. Chem. Phys., 26, 4359–4376, https://doi.org/10.5194/acp-26-4359-2026, https://doi.org/10.5194/acp-26-4359-2026, 2026
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In the Asian summer monsoon anticyclone the lapse rate tropopause, and not the cold point, constitutes a good estimate of the upper boundary of the well mixed tropospheric air mass. For strong convection there is substantial dehydration at the cold point tropopause (in summer 2017). Above the cold point tropopause, under such conditions, neither ice particle occurrence, nor enhanced molar mixing ratios of water vapour (above ≲ 6 ppm) are observed.
Sylvia C. Sullivan, Aiko Voigt, Edgardo Sepúlveda Araya, Silvia Bucci, Annette Miltenberger, Meredith K. Kupinski, Christian Rolf, and Martina Krämer
Atmos. Chem. Phys., 26, 1685–1698, https://doi.org/10.5194/acp-26-1685-2026, https://doi.org/10.5194/acp-26-1685-2026, 2026
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We assess the temperature, moisture, and dynamics in the upper troposphere-lower stratosphere simulated over South Asia in a high-resolution model relative to aircraft data. The lower stratosphere tends to be too warm, too dry, and too quiescent in the model, and as a result, too few ice clouds are predicted to form there. These biases could affect radiative balance and circulation in other areas also, as significant upward transport of moisture and pollutants occurs during the Asian monsoon.
Patrick Konjari, Christian Rolf, Martina Krämer, Armin Afchine, Nicole Spelten, Irene Bartolome Garcia, Annette Miltenberger, Nicolas Emig, Philipp Joppe, Johannes Schneider, Yun Li, Andreas Petzold, Heiko Bozem, and Peter Hoor
Atmos. Chem. Phys., 25, 18031–18050, https://doi.org/10.5194/acp-25-18031-2025, https://doi.org/10.5194/acp-25-18031-2025, 2025
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We investigated how a powerful storm over southern Sweden in June 2024 transported ice particles and moist air into the normally dry stratosphere. We observed unusually high water vapor and ice levels up to 1.5 kilometers above the tropopause. Although the extra water vapor lasted only a few days to weeks, it shows how such storms can temporarily alter the upper atmosphere’s composition.
Blaž Gasparini, Rachel Atlas, Aiko Voigt, Martina Krämer, and Peter N. Blossey
Atmos. Chem. Phys., 25, 9957–9979, https://doi.org/10.5194/acp-25-9957-2025, https://doi.org/10.5194/acp-25-9957-2025, 2025
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The evolution of tropical cirrus clouds is poorly understood, which contributes to large uncertainties in climate projections. To address this issue, we use novel tracers in a cloud-resolving model to track the life cycle of cirrus clouds. This approach provides insights into cloud formation, ice crystal evolution, and radiative effects of cirrus clouds. Additionally, we improve the model's cloud microphysics using a simple, computationally efficient approach that can be applied to other models.
Patrick Peter, Sigrun Matthes, Christine Frömming, Patrick Jöckel, Luca Bugliaro, Andreas Giez, Martina Krämer, and Volker Grewe
Atmos. Chem. Phys., 25, 5911–5934, https://doi.org/10.5194/acp-25-5911-2025, https://doi.org/10.5194/acp-25-5911-2025, 2025
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Our study examines how well the global climate model EMAC (ECHAM/MESSy Atmospheric Chemistry) predicts contrail formation by analysing temperature and humidity – two key factors for contrail development and persistence. The model underestimates temperature, leading to an overprediction of contrail formation and larger ice-supersaturated regions. Adjusting the model improves temperature accuracy but adds uncertainties. Better predictions of contrail formation areas can help optimise flight tracks to reduce aviation's climate effect.
Sreehari Kizhuveettil, Jordi Vila-Guerau de Arellano, Martina Krämer, Armin Afchine, Luiz A. T. Machado, Martin Zöger, and Wiebke Frey
EGUsphere, https://doi.org/10.5194/egusphere-2025-1637, https://doi.org/10.5194/egusphere-2025-1637, 2025
Preprint archived
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Aircraft measurements are used to investigate high-altitude downdrafts in tropical deep convective clouds. The cloud water present in the downdrafts and its intensity do not show any correlation. Surprisingly, downdrafts occurred in supersaturated regions, contradicting the classical view of subsaturated downdrafts. Up- and downdrafts of similar strength show similar particle size distributions. These findings shed new light on the interplay between deep convection dynamics and microphysics.
Patrick Konjari, Christian Rolf, Michaela I. Hegglin, Susanne Rohs, Yun Li, Andreas Zahn, Harald Bönisch, Philippe Nedelec, Martina Krämer, and Andreas Petzold
Atmos. Chem. Phys., 25, 4269–4289, https://doi.org/10.5194/acp-25-4269-2025, https://doi.org/10.5194/acp-25-4269-2025, 2025
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This study introduces a new method to derive adjusted water vapor (H2O) climatologies for the upper tropopshere and lower statosphere (UT/LS) using data from 60 000 flights under the IAGOS program. Biases in the IAGOS water vapour dataset are adjusted, based on the more accurate IAGOS-CARIBIC data. The resulting highly resolved H2O climatologies will contribute to a better understanding of the H2O variability in the UT/LS and its connection to various transport and mixing processes.
Ella Gilbert, Jhaswantsing Purseed, Yun Li, Martina Krämer, Beatrice Altamura, and Nicolas Bellouin
EGUsphere, https://doi.org/10.5194/egusphere-2024-821, https://doi.org/10.5194/egusphere-2024-821, 2024
Preprint withdrawn
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We use a simple experiment to explore the non-CO2 impacts of aviation on climate, which are considerably larger than the impact of the sector’s carbon emissions alone. We show that the main effect of our experiments – which intend to mimic the effect of aircraft soot emissions reaching existing high-altitude cirrus clouds – is to extend cloud lifetime, thereby enhancing their effect on climate.
Irene Bartolomé García, Odran Sourdeval, Reinhold Spang, and Martina Krämer
Atmos. Chem. Phys., 24, 1699–1716, https://doi.org/10.5194/acp-24-1699-2024, https://doi.org/10.5194/acp-24-1699-2024, 2024
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How many ice crystals of each size are in a cloud is a key parameter for the retrieval of cloud properties. The distribution of ice crystals is obtained from in situ measurements and used to create parameterizations that can be used when analyzing the remote-sensing data. Current parameterizations are based on data sets that do not include reliable measurements of small crystals, but in our study we use a data set that includes very small ice crystals to improve these parameterizations.
Francesco Cairo, Martina Krämer, Armin Afchine, Guido Di Donfrancesco, Luca Di Liberto, Sergey Khaykin, Lorenza Lucaferri, Valentin Mitev, Max Port, Christian Rolf, Marcel Snels, Nicole Spelten, Ralf Weigel, and Stephan Borrmann
Atmos. Meas. Tech., 16, 4899–4925, https://doi.org/10.5194/amt-16-4899-2023, https://doi.org/10.5194/amt-16-4899-2023, 2023
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Cirrus clouds have been observed over the Himalayan region between 10 km and the tropopause at 17–18 km. Data from backscattersonde, hygrometers, and particle cloud spectrometers have been compared to assess their consistency. Empirical relationships between optical parameters accessible with remote sensing lidars and cloud microphysical parameters (such as ice water content, particle number and surface area density, and particle aspherical fraction) have been established.
Elena De La Torre Castro, Tina Jurkat-Witschas, Armin Afchine, Volker Grewe, Valerian Hahn, Simon Kirschler, Martina Krämer, Johannes Lucke, Nicole Spelten, Heini Wernli, Martin Zöger, and Christiane Voigt
Atmos. Chem. Phys., 23, 13167–13189, https://doi.org/10.5194/acp-23-13167-2023, https://doi.org/10.5194/acp-23-13167-2023, 2023
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In this study, we show the differences in the microphysical properties between high-latitude (HL) cirrus and mid-latitude (ML) cirrus over the Arctic, North Atlantic, and central Europe during summer. The in situ measurements are combined with backward trajectories to investigate the influence of the region on cloud formation. We show that HL cirrus are characterized by a lower concentration of larger ice crystals when compared to ML cirrus.
Paul Konopka, Christian Rolf, Marc von Hobe, Sergey M. Khaykin, Benjamin Clouser, Elisabeth Moyer, Fabrizio Ravegnani, Francesco D'Amato, Silvia Viciani, Nicole Spelten, Armin Afchine, Martina Krämer, Fred Stroh, and Felix Ploeger
Atmos. Chem. Phys., 23, 12935–12947, https://doi.org/10.5194/acp-23-12935-2023, https://doi.org/10.5194/acp-23-12935-2023, 2023
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We studied water vapor in a critical region of the atmosphere, the Asian summer monsoon anticyclone, using rare in situ observations. Our study shows that extremely high water vapor values observed in the stratosphere within the Asian monsoon anticyclone still undergo significant freeze-drying and that water vapor concentrations set by the Lagrangian dry point are a better proxy for the stratospheric water vapor budget than rare observations of enhanced water mixing ratios.
Silke Groß, Tina Jurkat-Witschas, Qiang Li, Martin Wirth, Benedikt Urbanek, Martina Krämer, Ralf Weigel, and Christiane Voigt
Atmos. Chem. Phys., 23, 8369–8381, https://doi.org/10.5194/acp-23-8369-2023, https://doi.org/10.5194/acp-23-8369-2023, 2023
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Aviation-emitted aerosol can have an impact on cirrus clouds. We present optical and microphysical properties of mid-latitude cirrus clouds which were formed under the influence of aviation-emitted aerosol or which were formed under rather pristine conditions. We find that cirrus clouds affected by aviation-emitted aerosol show larger values of the particle linear depolarization ratio, larger mean effective ice particle diameters and decreased ice particle number concentrations.
Georgios Dekoutsidis, Silke Groß, Martin Wirth, Martina Krämer, and Christian Rolf
Atmos. Chem. Phys., 23, 3103–3117, https://doi.org/10.5194/acp-23-3103-2023, https://doi.org/10.5194/acp-23-3103-2023, 2023
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Cirrus clouds affect Earth's atmosphere, deeming our study important. Here we use water vapor measurements by lidar and study the relative humidity (RHi) within and around midlatitude cirrus clouds. We find high supersaturations in the cloud-free air and within the clouds, especially near the cloud top. We study two cloud types with different formation processes. Finally, we conclude that the shape of the distribution of RHi can be used as an indicator of different cloud evolutionary stages.
Fayçal Lamraoui, Martina Krämer, Armin Afchine, Adam B. Sokol, Sergey Khaykin, Apoorva Pandey, and Zhiming Kuang
Atmos. Chem. Phys., 23, 2393–2419, https://doi.org/10.5194/acp-23-2393-2023, https://doi.org/10.5194/acp-23-2393-2023, 2023
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Cirrus in the tropical tropopause layer (TTL) can play a key role in vertical transport. We investigate the role of different cloud regimes and the associated ice habits in regulating the properties of the TTL. We use high-resolution numerical experiments at the scales of large-eddy simulations (LESs) and aircraft measurements. We found that LES-scale parameterizations that predict ice shape are crucial for an accurate representation of TTL cirrus and thus the associated (de)hydration process.
Yun Li, Christoph Mahnke, Susanne Rohs, Ulrich Bundke, Nicole Spelten, Georgios Dekoutsidis, Silke Groß, Christiane Voigt, Ulrich Schumann, Andreas Petzold, and Martina Krämer
Atmos. Chem. Phys., 23, 2251–2271, https://doi.org/10.5194/acp-23-2251-2023, https://doi.org/10.5194/acp-23-2251-2023, 2023
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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.
Andreas Marsing, Ralf Meerkötter, Romy Heller, Stefan Kaufmann, Tina Jurkat-Witschas, Martina Krämer, Christian Rolf, and Christiane Voigt
Atmos. Chem. Phys., 23, 587–609, https://doi.org/10.5194/acp-23-587-2023, https://doi.org/10.5194/acp-23-587-2023, 2023
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We employ highly resolved aircraft measurements of profiles of the ice water content (IWC) in Arctic cirrus clouds in winter and spring, when solar irradiation is low. Using radiation transfer calculations, we assess the cloud radiative effect over different surfaces like snow or ocean. The variability in the IWC of the clouds affects their overall radiative effect and drives internal processes. This helps understand the role of cirrus in a rapidly changing Arctic environment.
Clare E. Singer, Benjamin W. Clouser, Sergey M. Khaykin, Martina Krämer, Francesco Cairo, Thomas Peter, Alexey Lykov, Christian Rolf, Nicole Spelten, Armin Afchine, Simone Brunamonti, and Elisabeth J. Moyer
Atmos. Meas. Tech., 15, 4767–4783, https://doi.org/10.5194/amt-15-4767-2022, https://doi.org/10.5194/amt-15-4767-2022, 2022
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In situ measurements of water vapor in the upper troposphere are necessary to study cloud formation and hydration of the stratosphere but challenging due to cold–dry conditions. We compare measurements from three water vapor instruments from the StratoClim campaign in 2017. In clear sky (clouds), point-by-point differences were <1.5±8 % (<1±8 %). This excellent agreement allows detection of fine-scale structures required to understand the impact of convection on stratospheric water vapor.
Mireia Papke Chica, Valerian Hahn, Tiziana Braeuer, Elena de la Torre Castro, Florian Ewald, Mathias Gergely, Simon Kirschler, Luca Bugliaro Goggia, Stefanie Knobloch, Martina Kraemer, Johannes Lucke, Johanna Mayer, Raphael Maerkl, Manuel Moser, Laura Tomsche, Tina Jurkat-Witschas, Martin Zoeger, Christian von Savigny, and Christiane Voigt
Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2022-255, https://doi.org/10.5194/acp-2022-255, 2022
Preprint withdrawn
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The mixed-phase temperature regime in convective clouds challenges our understanding of microphysical and radiative cloud properties. We provide a rare and unique dataset of aircraft in situ measurements in a strong mid-latitude convective system. We find that mechanisms initiating ice nucleation and growth strongly depend on temperature, relative humidity, and vertical velocity and variate within the measured system, resulting in altitude dependent changes of the cloud liquid and ice fraction.
Sergey M. Khaykin, Elizabeth Moyer, Martina Krämer, Benjamin Clouser, Silvia Bucci, Bernard Legras, Alexey Lykov, Armin Afchine, Francesco Cairo, Ivan Formanyuk, Valentin Mitev, Renaud Matthey, Christian Rolf, Clare E. Singer, Nicole Spelten, Vasiliy Volkov, Vladimir Yushkov, and Fred Stroh
Atmos. Chem. Phys., 22, 3169–3189, https://doi.org/10.5194/acp-22-3169-2022, https://doi.org/10.5194/acp-22-3169-2022, 2022
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The Asian monsoon anticyclone is the key contributor to the global annual maximum in lower stratospheric water vapour. We investigate the impact of deep convection on the lower stratospheric water using a unique set of observations aboard the high-altitude M55-Geophysica aircraft deployed in Nepal in summer 2017 within the EU StratoClim project. We find that convective plumes of wet air can persist within the Asian anticyclone for weeks, thereby enhancing the occurrence of high-level clouds.
Dina Khordakova, Christian Rolf, Jens-Uwe Grooß, Rolf Müller, Paul Konopka, Andreas Wieser, Martina Krämer, and Martin Riese
Atmos. Chem. Phys., 22, 1059–1079, https://doi.org/10.5194/acp-22-1059-2022, https://doi.org/10.5194/acp-22-1059-2022, 2022
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Extreme storms transport humidity from the troposphere to the stratosphere. Here it has a strong impact on the climate. With ongoing global warming, we expect more storms and, hence, an enhancement of this effect. A case study was performed in order to measure the impact of the direct injection of water vapor into the lower stratosphere. The measurements displayed a significant transport of water vapor into the lower stratosphere, and this was supported by satellite and reanalysis data.
Manuel Baumgartner, Christian Rolf, Jens-Uwe Grooß, Julia Schneider, Tobias Schorr, Ottmar Möhler, Peter Spichtinger, and Martina Krämer
Atmos. Chem. Phys., 22, 65–91, https://doi.org/10.5194/acp-22-65-2022, https://doi.org/10.5194/acp-22-65-2022, 2022
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An important mechanism for the appearance of ice particles in the upper troposphere at low temperatures is homogeneous nucleation. This process is commonly described by the
Koop line, predicting the humidity at freezing. However, laboratory measurements suggest that the freezing humidities are above the Koop line, motivating the present study to investigate the influence of different physical parameterizations on the homogeneous freezing with the help of a detailed numerical model.
Christoph Mahnke, Ralf Weigel, Francesco Cairo, Jean-Paul Vernier, Armin Afchine, Martina Krämer, Valentin Mitev, Renaud Matthey, Silvia Viciani, Francesco D'Amato, Felix Ploeger, Terry Deshler, and Stephan Borrmann
Atmos. Chem. Phys., 21, 15259–15282, https://doi.org/10.5194/acp-21-15259-2021, https://doi.org/10.5194/acp-21-15259-2021, 2021
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In 2017, in situ aerosol measurements were conducted aboard the M55 Geophysica in the Asian monsoon region. The vertical particle mixing ratio profiles show a distinct layer (15–18.5 km), the Asian tropopause aerosol layer (ATAL). The backscatter ratio (BR) was calculated based on the aerosol size distributions and compared with the BRs detected by a backscatter probe and a lidar aboard M55, and by the CALIOP lidar. All four methods show enhanced BRs in the ATAL altitude range (max. at 17.5 km).
Julia Schneider, Kristina Höhler, Robert Wagner, Harald Saathoff, Martin Schnaiter, Tobias Schorr, Isabelle Steinke, Stefan Benz, Manuel Baumgartner, Christian Rolf, Martina Krämer, Thomas Leisner, and Ottmar Möhler
Atmos. Chem. Phys., 21, 14403–14425, https://doi.org/10.5194/acp-21-14403-2021, https://doi.org/10.5194/acp-21-14403-2021, 2021
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Homogeneous freezing is a relevant mechanism for the formation of cirrus clouds in the upper troposphere. Based on an extensive set of homogeneous freezing experiments at the AIDA chamber with aqueous sulfuric acid aerosol, we provide a new fit line for homogeneous freezing onset conditions of sulfuric acid aerosol focusing on cirrus temperatures. In the atmosphere, homogeneous freezing thresholds have important implications on the cirrus cloud occurrence and related cloud radiative effects.
Nicolas Emig, Annette Miltenberger, Heiko Bozem, Martina Krämer, Armin Afchine, Daniel Kunkel, Hans-Christoph Lachnitt, Yun Li, Philipp Reutter, Christian Rolf, Nicole Spelten, Holger Tost, and Peter Hoor
EGUsphere, https://doi.org/10.5194/egusphere-2026-4614, https://doi.org/10.5194/egusphere-2026-4614, 2026
This preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).
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In this study we show mixing of ice particles across the extratropical tropopause via turbulence in the jet shear zone based on in situ measurements from the TPEx campaign over the North Sea, combined with Lagrangian model analysis. Trace gas correlations and subsaturated ice particles constrain the timing and mechanism, while backward trajectories indicate suitable turbulent conditions beforehand. This process possibly impacts the water vapour budget of the extratropical lowermost stratosphere.
Mélanie Ghysels, Luca Palchetti, Silvia Viciani, Claudio Belotti, Marco Barucci, Gwenaël Berthet, Elizabeth Asher, Emrys Hall, Alex Fritz, Armin Afchine, Christian Rolf, Thomas Kuhn, Chris Stopford, Alain Hauchecorne, Nadir Amarouche, Georges Durry, Jean-Christophe Samake, Lars E. Kalnajs, Terry Deshler, Samuele Del Bianco, and Paolo Pettinari
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2026-557, https://doi.org/10.5194/essd-2026-557, 2026
Preprint under review for ESSD
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ATMOSFER, a CNES-supported 2024 balloon campaign in Kiruna, Sweden, prepared ESA’s FORUM mission by measuring far-infrared radiation, water vapor, clouds and aerosols in the UTLS. FIRMOS-B (balloon borne demonstrator of FORUM) showed excellent performance, while hygrometers agreed closely. The campaign observed cirrus clouds, ice crystals and stratospheric aerosol layers linked to wildfire and tropical air masses, improving climate observations and FORUM validation.
Georgios Dekoutsidis, Silke Groß, Florian Ewald, Martina Krämer, Christian Rolf, Andreas Schäfler, and Martin Wirth
EGUsphere, https://doi.org/10.5194/egusphere-2026-3788, https://doi.org/10.5194/egusphere-2026-3788, 2026
This preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).
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Cirrus clouds interact with radiation, but their exact effects are not well-defined and depend on their properties, formation process and the ambient conditions. We used airborne lidar and radar measurements and models in order to compare cirrus that formed in undisturbed conditions and during Warm Air intrusions (WAI). We found that WAIs cause a change in the formation and their properties. Our findings can improve the representation of cirrus in models and the estimation of their impact.
Kasper Juurikkala, Tomi Raatikainen, Martina Krämer, Christina J. Williamson, and Ari Laaksonen
EGUsphere, https://doi.org/10.5194/egusphere-2026-2427, https://doi.org/10.5194/egusphere-2026-2427, 2026
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We use large-eddy simulations constrained by observations to study how mineral dust controls the evolution of cirrus clouds during dust outbreaks. Results show that sustained dusty cirrus forms only under strongly elevated dust concentrations, where ice forms mainly on dust particles. This identifies mineral dust as the key control on cirrus persistence and highlights the need to improve representation of dust-driven ice formation in weather and climate models.
Bärbel Vogel, Valentin Lauther, Franziska Köllner, Fatih Ekinci, Christian Rolf, Johannes Strobel, Ronja van Luijt, C. Michael Volk, Stephan Borrmann, Antonis Dragoneas, Oliver Eppers, Sergej Molleker, Peter Hoor, Linda Ort, Franziska Weyland, Andreas Zahn, Jan Clemens, Gebhard Günther, Oleh Kachula, Rolf Müller, Felix Ploeger, and Martin Riese
Atmos. Chem. Phys., 26, 6283–6319, https://doi.org/10.5194/acp-26-6283-2026, https://doi.org/10.5194/acp-26-6283-2026, 2026
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This work highlights the impact of the Asian summer monsoon on the chemical composition of the upper troposphere and lower stratosphere. Measurements of trace gases and aerosol particles uplifted by the Asian summer monsoon to higher altitudes are sparse. Here, we had the opportunity to use a whole suite of different measured trace gases and the chemical composition of aerosols, in combination with simulations, to better understand the complex transport and mixing processes in this region.
Athulya Saiprakash, Martina Krämer, Christian Rolf, Jérôme Riedi, and Odran Sourdeval
EGUsphere, https://doi.org/10.5194/egusphere-2026-2423, https://doi.org/10.5194/egusphere-2026-2423, 2026
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This second part of the study tested the new method by comparing its results with satellite and aircraft observations and by examining how sensitive it is to key assumptions. The method agreed well with observations in most cases, although clouds formed over mountains remained harder to capture. It also showed which conditions and processes matter most for reconstructing how cirrus form and evolve.
Athulya Saiprakash, Martina Krämer, Christian Rolf, Patrick Konjari, Jérôme Riedi, and Odran Sourdeval
EGUsphere, https://doi.org/10.5194/egusphere-2026-2416, https://doi.org/10.5194/egusphere-2026-2416, 2026
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To better understand how observed high ice clouds, known as cirrus, form and change, satellite images were combined with calculations that reconstruct how the air moved before the clouds formed. Case studies showed that cloud history differs with height, age, and surrounding conditions, and that small temperature changes strongly shape cloud growth. This helps reveal and characterize the mechanisms behind observed cirrus.
Rolf Müller, Bärbel Vogel, Martina Krämer, Christian Rolf, Nicole Spelten, and Fabrizio Ravegnani
Atmos. Chem. Phys., 26, 4359–4376, https://doi.org/10.5194/acp-26-4359-2026, https://doi.org/10.5194/acp-26-4359-2026, 2026
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In the Asian summer monsoon anticyclone the lapse rate tropopause, and not the cold point, constitutes a good estimate of the upper boundary of the well mixed tropospheric air mass. For strong convection there is substantial dehydration at the cold point tropopause (in summer 2017). Above the cold point tropopause, under such conditions, neither ice particle occurrence, nor enhanced molar mixing ratios of water vapour (above ≲ 6 ppm) are observed.
Sylvia C. Sullivan, Aiko Voigt, Edgardo Sepúlveda Araya, Silvia Bucci, Annette Miltenberger, Meredith K. Kupinski, Christian Rolf, and Martina Krämer
Atmos. Chem. Phys., 26, 1685–1698, https://doi.org/10.5194/acp-26-1685-2026, https://doi.org/10.5194/acp-26-1685-2026, 2026
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We assess the temperature, moisture, and dynamics in the upper troposphere-lower stratosphere simulated over South Asia in a high-resolution model relative to aircraft data. The lower stratosphere tends to be too warm, too dry, and too quiescent in the model, and as a result, too few ice clouds are predicted to form there. These biases could affect radiative balance and circulation in other areas also, as significant upward transport of moisture and pollutants occurs during the Asian monsoon.
Patrick Konjari, Christian Rolf, Martina Krämer, Armin Afchine, Nicole Spelten, Irene Bartolome Garcia, Annette Miltenberger, Nicolas Emig, Philipp Joppe, Johannes Schneider, Yun Li, Andreas Petzold, Heiko Bozem, and Peter Hoor
Atmos. Chem. Phys., 25, 18031–18050, https://doi.org/10.5194/acp-25-18031-2025, https://doi.org/10.5194/acp-25-18031-2025, 2025
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We investigated how a powerful storm over southern Sweden in June 2024 transported ice particles and moist air into the normally dry stratosphere. We observed unusually high water vapor and ice levels up to 1.5 kilometers above the tropopause. Although the extra water vapor lasted only a few days to weeks, it shows how such storms can temporarily alter the upper atmosphere’s composition.
Heiko Bozem, Philipp Joppe, Yun Li, Nicolas Emig, Armin Afchine, Anna Breuninger, Joachim Curtius, Stefan Hofmann, Sadath Ismayil, Konrad Kandler, Daniel Kunkel, Arthur Kutschka, Hans-Christoph Lachnitt, Andreas Petzold, Sarah Richter, Timo Röschenthaler, Christian Rolf, Lisa Schneider, Johannes Schneider, Alexander Vogel, and Peter Hoor
Atmos. Meas. Tech., 18, 6545–6568, https://doi.org/10.5194/amt-18-6545-2025, https://doi.org/10.5194/amt-18-6545-2025, 2025
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Deployed on a Learjet as a tandem measurement platform during the TPEx I (TropoPause composition gradients and mixing Experiment) campaign in June 2024, the new TPC-TOSS (TropoPause Composition Towed Sensor Shuttle) system delivers high-resolution in situ data on ozone, aerosol, and key meteorological parameters. Laboratory and in-flight tests confirmed its precision and stability. Observed gradients near the tropopause reveal active mixing and transport processes in the tropopause region.
Philipp Joppe, Johannes Schneider, Jonas Wilsch, Heiko Bozem, Anna Breuninger, Joachim Curtius, Martin Ebert, Nicolas Emig, Peter Hoor, Sadath Ismayil, Konrad Kandler, Daniel Kunkel, Isabel Kurth, Hans-Christoph Lachnitt, Yun Li, Annette Miltenberger, Sarah Richter, Christian Rolf, Lisa Schneider, Cornelis Schwenk, Nicole Spelten, Alexander L. Vogel, Yafang Cheng, and Stephan Borrmann
Atmos. Chem. Phys., 25, 15077–15103, https://doi.org/10.5194/acp-25-15077-2025, https://doi.org/10.5194/acp-25-15077-2025, 2025
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We show measurements of a filament with biomass burning influence transported by a warm conveyor belt (WCB) into the tropopause region over Europe. The pollution originates from Canadian forest fires and is transported in the lower troposphere towards Europe. The WCB transport is followed by mixing with air masses of stratospheric chemical signatures. We hypothesize that this mixing leads to a change in the vertical gradient of the potential temperature.
Blaž Gasparini, Rachel Atlas, Aiko Voigt, Martina Krämer, and Peter N. Blossey
Atmos. Chem. Phys., 25, 9957–9979, https://doi.org/10.5194/acp-25-9957-2025, https://doi.org/10.5194/acp-25-9957-2025, 2025
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The evolution of tropical cirrus clouds is poorly understood, which contributes to large uncertainties in climate projections. To address this issue, we use novel tracers in a cloud-resolving model to track the life cycle of cirrus clouds. This approach provides insights into cloud formation, ice crystal evolution, and radiative effects of cirrus clouds. Additionally, we improve the model's cloud microphysics using a simple, computationally efficient approach that can be applied to other models.
Patrick Peter, Sigrun Matthes, Christine Frömming, Patrick Jöckel, Luca Bugliaro, Andreas Giez, Martina Krämer, and Volker Grewe
Atmos. Chem. Phys., 25, 5911–5934, https://doi.org/10.5194/acp-25-5911-2025, https://doi.org/10.5194/acp-25-5911-2025, 2025
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Our study examines how well the global climate model EMAC (ECHAM/MESSy Atmospheric Chemistry) predicts contrail formation by analysing temperature and humidity – two key factors for contrail development and persistence. The model underestimates temperature, leading to an overprediction of contrail formation and larger ice-supersaturated regions. Adjusting the model improves temperature accuracy but adds uncertainties. Better predictions of contrail formation areas can help optimise flight tracks to reduce aviation's climate effect.
Sreehari Kizhuveettil, Jordi Vila-Guerau de Arellano, Martina Krämer, Armin Afchine, Luiz A. T. Machado, Martin Zöger, and Wiebke Frey
EGUsphere, https://doi.org/10.5194/egusphere-2025-1637, https://doi.org/10.5194/egusphere-2025-1637, 2025
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Aircraft measurements are used to investigate high-altitude downdrafts in tropical deep convective clouds. The cloud water present in the downdrafts and its intensity do not show any correlation. Surprisingly, downdrafts occurred in supersaturated regions, contradicting the classical view of subsaturated downdrafts. Up- and downdrafts of similar strength show similar particle size distributions. These findings shed new light on the interplay between deep convection dynamics and microphysics.
Patrick Konjari, Christian Rolf, Michaela I. Hegglin, Susanne Rohs, Yun Li, Andreas Zahn, Harald Bönisch, Philippe Nedelec, Martina Krämer, and Andreas Petzold
Atmos. Chem. Phys., 25, 4269–4289, https://doi.org/10.5194/acp-25-4269-2025, https://doi.org/10.5194/acp-25-4269-2025, 2025
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This study introduces a new method to derive adjusted water vapor (H2O) climatologies for the upper tropopshere and lower statosphere (UT/LS) using data from 60 000 flights under the IAGOS program. Biases in the IAGOS water vapour dataset are adjusted, based on the more accurate IAGOS-CARIBIC data. The resulting highly resolved H2O climatologies will contribute to a better understanding of the H2O variability in the UT/LS and its connection to various transport and mixing processes.
Ling Zou, Reinhold Spang, Sabine Griessbach, Lars Hoffmann, Farahnaz Khosrawi, Rolf Müller, and Ines Tritscher
Atmos. Chem. Phys., 24, 11759–11774, https://doi.org/10.5194/acp-24-11759-2024, https://doi.org/10.5194/acp-24-11759-2024, 2024
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This study provided estimates of the occurrence of ice polar stratospheric clouds (PSCs) observed by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and their connection with temperatures above the frost point (Tice) using a Lagrangian model derived from ERA5. We found that ice PSCs above Tice with temperature fluctuations along the backward trajectory are 33 % in the Arctic and 9 % in the Antarctic. This quantitative assessment enhances our understanding of ice PSCs.
Hengheng Zhang, Christian Rolf, Ralf Tillmann, Christian Wesolek, Frank Gunther Wienhold, Thomas Leisner, and Harald Saathoff
Aerosol Research, 2, 135–151, https://doi.org/10.5194/ar-2-135-2024, https://doi.org/10.5194/ar-2-135-2024, 2024
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Our study employs advanced tools, including scanning lidar, balloons, and UAVs, to explore aerosol particles in the atmosphere. The scanning lidar offers distinctive near-ground-level insights, enriching our comprehension of aerosol distribution from ground level to the free troposphere. This research provides valuable data for comparing remote sensing and in situ aerosol measurements, advancing our understanding of aerosol impacts on radiative transfer, clouds, and air quality.
Ella Gilbert, Jhaswantsing Purseed, Yun Li, Martina Krämer, Beatrice Altamura, and Nicolas Bellouin
EGUsphere, https://doi.org/10.5194/egusphere-2024-821, https://doi.org/10.5194/egusphere-2024-821, 2024
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We use a simple experiment to explore the non-CO2 impacts of aviation on climate, which are considerably larger than the impact of the sector’s carbon emissions alone. We show that the main effect of our experiments – which intend to mimic the effect of aircraft soot emissions reaching existing high-altitude cirrus clouds – is to extend cloud lifetime, thereby enhancing their effect on climate.
Irene Bartolomé García, Odran Sourdeval, Reinhold Spang, and Martina Krämer
Atmos. Chem. Phys., 24, 1699–1716, https://doi.org/10.5194/acp-24-1699-2024, https://doi.org/10.5194/acp-24-1699-2024, 2024
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How many ice crystals of each size are in a cloud is a key parameter for the retrieval of cloud properties. The distribution of ice crystals is obtained from in situ measurements and used to create parameterizations that can be used when analyzing the remote-sensing data. Current parameterizations are based on data sets that do not include reliable measurements of small crystals, but in our study we use a data set that includes very small ice crystals to improve these parameterizations.
Reinhold Spang, Rolf Müller, and Alexandru Rap
Atmos. Chem. Phys., 24, 1213–1230, https://doi.org/10.5194/acp-24-1213-2024, https://doi.org/10.5194/acp-24-1213-2024, 2024
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Cirrus clouds play an important role in the radiation budget of the Earth. Despite recent progress in their observation, the radiative impact of ultra-thin cirrus clouds (UTC) in the tropopause region and in the lowermost stratosphere remains poorly constrained. Sensitivity model simulations with different ice parameters provide an uncertainty range for the radiative effect of UTCs. There is a need for better observed UTCs to enable the simulation of their potentially large effect on climate.
Thomas Trickl, Martin Adelwart, Dina Khordakova, Ludwig Ries, Christian Rolf, Michael Sprenger, Wolfgang Steinbrecht, and Hannes Vogelmann
Atmos. Meas. Tech., 16, 5145–5165, https://doi.org/10.5194/amt-16-5145-2023, https://doi.org/10.5194/amt-16-5145-2023, 2023
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Tropospheric ozone have been measured for more than a century. Highly quantitative ozone measurements have been made at monitoring stations. However, deficits have been reported for vertical sounding systems. Here, we report a thorough intercomparison effort between a differential-absorption lidar system and two types of balloon-borne ozone sondes, also using ozone sensors at nearby mountain sites as references. The sondes agree very well with the lidar after offset corrections.
Francesco Cairo, Martina Krämer, Armin Afchine, Guido Di Donfrancesco, Luca Di Liberto, Sergey Khaykin, Lorenza Lucaferri, Valentin Mitev, Max Port, Christian Rolf, Marcel Snels, Nicole Spelten, Ralf Weigel, and Stephan Borrmann
Atmos. Meas. Tech., 16, 4899–4925, https://doi.org/10.5194/amt-16-4899-2023, https://doi.org/10.5194/amt-16-4899-2023, 2023
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Cirrus clouds have been observed over the Himalayan region between 10 km and the tropopause at 17–18 km. Data from backscattersonde, hygrometers, and particle cloud spectrometers have been compared to assess their consistency. Empirical relationships between optical parameters accessible with remote sensing lidars and cloud microphysical parameters (such as ice water content, particle number and surface area density, and particle aspherical fraction) have been established.
Elena De La Torre Castro, Tina Jurkat-Witschas, Armin Afchine, Volker Grewe, Valerian Hahn, Simon Kirschler, Martina Krämer, Johannes Lucke, Nicole Spelten, Heini Wernli, Martin Zöger, and Christiane Voigt
Atmos. Chem. Phys., 23, 13167–13189, https://doi.org/10.5194/acp-23-13167-2023, https://doi.org/10.5194/acp-23-13167-2023, 2023
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In this study, we show the differences in the microphysical properties between high-latitude (HL) cirrus and mid-latitude (ML) cirrus over the Arctic, North Atlantic, and central Europe during summer. The in situ measurements are combined with backward trajectories to investigate the influence of the region on cloud formation. We show that HL cirrus are characterized by a lower concentration of larger ice crystals when compared to ML cirrus.
Paul Konopka, Christian Rolf, Marc von Hobe, Sergey M. Khaykin, Benjamin Clouser, Elisabeth Moyer, Fabrizio Ravegnani, Francesco D'Amato, Silvia Viciani, Nicole Spelten, Armin Afchine, Martina Krämer, Fred Stroh, and Felix Ploeger
Atmos. Chem. Phys., 23, 12935–12947, https://doi.org/10.5194/acp-23-12935-2023, https://doi.org/10.5194/acp-23-12935-2023, 2023
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We studied water vapor in a critical region of the atmosphere, the Asian summer monsoon anticyclone, using rare in situ observations. Our study shows that extremely high water vapor values observed in the stratosphere within the Asian monsoon anticyclone still undergo significant freeze-drying and that water vapor concentrations set by the Lagrangian dry point are a better proxy for the stratospheric water vapor budget than rare observations of enhanced water mixing ratios.
Silke Groß, Tina Jurkat-Witschas, Qiang Li, Martin Wirth, Benedikt Urbanek, Martina Krämer, Ralf Weigel, and Christiane Voigt
Atmos. Chem. Phys., 23, 8369–8381, https://doi.org/10.5194/acp-23-8369-2023, https://doi.org/10.5194/acp-23-8369-2023, 2023
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Aviation-emitted aerosol can have an impact on cirrus clouds. We present optical and microphysical properties of mid-latitude cirrus clouds which were formed under the influence of aviation-emitted aerosol or which were formed under rather pristine conditions. We find that cirrus clouds affected by aviation-emitted aerosol show larger values of the particle linear depolarization ratio, larger mean effective ice particle diameters and decreased ice particle number concentrations.
Claudio Belotti, Flavio Barbara, Marco Barucci, Giovanni Bianchini, Francesco D'Amato, Samuele Del Bianco, Gianluca Di Natale, Marco Gai, Alessio Montori, Filippo Pratesi, Markus Rettinger, Christian Rolf, Ralf Sussmann, Thomas Trickl, Silvia Viciani, Hannes Vogelmann, and Luca Palchetti
Atmos. Meas. Tech., 16, 2511–2529, https://doi.org/10.5194/amt-16-2511-2023, https://doi.org/10.5194/amt-16-2511-2023, 2023
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FIRMOS (Far-Infrared Radiation Mobile Observation System) is a spectroradiometer measuring in the far-infrared, developed to support the preparation of the FORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) satellite mission. In this paper, we describe the instrument, its data products, and the results of the comparison with a suite of observations made from a high-altitude site during a field campaign, in winter 2018–2019.
Georgios Dekoutsidis, Silke Groß, Martin Wirth, Martina Krämer, and Christian Rolf
Atmos. Chem. Phys., 23, 3103–3117, https://doi.org/10.5194/acp-23-3103-2023, https://doi.org/10.5194/acp-23-3103-2023, 2023
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Cirrus clouds affect Earth's atmosphere, deeming our study important. Here we use water vapor measurements by lidar and study the relative humidity (RHi) within and around midlatitude cirrus clouds. We find high supersaturations in the cloud-free air and within the clouds, especially near the cloud top. We study two cloud types with different formation processes. Finally, we conclude that the shape of the distribution of RHi can be used as an indicator of different cloud evolutionary stages.
Fayçal Lamraoui, Martina Krämer, Armin Afchine, Adam B. Sokol, Sergey Khaykin, Apoorva Pandey, and Zhiming Kuang
Atmos. Chem. Phys., 23, 2393–2419, https://doi.org/10.5194/acp-23-2393-2023, https://doi.org/10.5194/acp-23-2393-2023, 2023
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Cirrus in the tropical tropopause layer (TTL) can play a key role in vertical transport. We investigate the role of different cloud regimes and the associated ice habits in regulating the properties of the TTL. We use high-resolution numerical experiments at the scales of large-eddy simulations (LESs) and aircraft measurements. We found that LES-scale parameterizations that predict ice shape are crucial for an accurate representation of TTL cirrus and thus the associated (de)hydration process.
Yun Li, Christoph Mahnke, Susanne Rohs, Ulrich Bundke, Nicole Spelten, Georgios Dekoutsidis, Silke Groß, Christiane Voigt, Ulrich Schumann, Andreas Petzold, and Martina Krämer
Atmos. Chem. Phys., 23, 2251–2271, https://doi.org/10.5194/acp-23-2251-2023, https://doi.org/10.5194/acp-23-2251-2023, 2023
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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.
Andreas Marsing, Ralf Meerkötter, Romy Heller, Stefan Kaufmann, Tina Jurkat-Witschas, Martina Krämer, Christian Rolf, and Christiane Voigt
Atmos. Chem. Phys., 23, 587–609, https://doi.org/10.5194/acp-23-587-2023, https://doi.org/10.5194/acp-23-587-2023, 2023
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We employ highly resolved aircraft measurements of profiles of the ice water content (IWC) in Arctic cirrus clouds in winter and spring, when solar irradiation is low. Using radiation transfer calculations, we assess the cloud radiative effect over different surfaces like snow or ocean. The variability in the IWC of the clouds affects their overall radiative effect and drives internal processes. This helps understand the role of cirrus in a rapidly changing Arctic environment.
Clare E. Singer, Benjamin W. Clouser, Sergey M. Khaykin, Martina Krämer, Francesco Cairo, Thomas Peter, Alexey Lykov, Christian Rolf, Nicole Spelten, Armin Afchine, Simone Brunamonti, and Elisabeth J. Moyer
Atmos. Meas. Tech., 15, 4767–4783, https://doi.org/10.5194/amt-15-4767-2022, https://doi.org/10.5194/amt-15-4767-2022, 2022
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In situ measurements of water vapor in the upper troposphere are necessary to study cloud formation and hydration of the stratosphere but challenging due to cold–dry conditions. We compare measurements from three water vapor instruments from the StratoClim campaign in 2017. In clear sky (clouds), point-by-point differences were <1.5±8 % (<1±8 %). This excellent agreement allows detection of fine-scale structures required to understand the impact of convection on stratospheric water vapor.
Ling Zou, Sabine Griessbach, Lars Hoffmann, and Reinhold Spang
Atmos. Chem. Phys., 22, 6677–6702, https://doi.org/10.5194/acp-22-6677-2022, https://doi.org/10.5194/acp-22-6677-2022, 2022
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Ice clouds in the stratosphere (SICs) greatly affect the water vapor balance and radiation budget in the upper troposphere and lower stratosphere (UTLS). We quantified the global SICs and analyzed their relationships with tropopause temperature, double tropopauses, UTLS clouds, gravity waves, and stratospheric aerosols. The correlations between SICs and all abovementioned processes indicate that the occurrence of and variability in SICs are spatiotemporally dependent on different processes.
Andreas Wieser, Andreas Güntner, Peter Dietrich, Jan Handwerker, Dina Khordakova, Uta Ködel, Martin Kohler, Hannes Mollenhauer, Bernhard Mühr, Erik Nixdorf, Marvin Reich, Christian Rolf, Martin Schrön, Claudia Schütze, and Ute Weber
Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2022-131, https://doi.org/10.5194/hess-2022-131, 2022
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We present an event-triggered observation concept which covers the entire process chain from heavy precipitation to flooding at the catchment scale. It combines flexible and mobile observing systems out of the fields of meteorology, hydrology and geophysics with stationary networks to capture atmospheric transport processes, heterogeneous precipitation patterns, land surface and subsurface storage processes, and runoff dynamics.
Mireia Papke Chica, Valerian Hahn, Tiziana Braeuer, Elena de la Torre Castro, Florian Ewald, Mathias Gergely, Simon Kirschler, Luca Bugliaro Goggia, Stefanie Knobloch, Martina Kraemer, Johannes Lucke, Johanna Mayer, Raphael Maerkl, Manuel Moser, Laura Tomsche, Tina Jurkat-Witschas, Martin Zoeger, Christian von Savigny, and Christiane Voigt
Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2022-255, https://doi.org/10.5194/acp-2022-255, 2022
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The mixed-phase temperature regime in convective clouds challenges our understanding of microphysical and radiative cloud properties. We provide a rare and unique dataset of aircraft in situ measurements in a strong mid-latitude convective system. We find that mechanisms initiating ice nucleation and growth strongly depend on temperature, relative humidity, and vertical velocity and variate within the measured system, resulting in altitude dependent changes of the cloud liquid and ice fraction.
Lars Hoffmann and Reinhold Spang
Atmos. Chem. Phys., 22, 4019–4046, https://doi.org/10.5194/acp-22-4019-2022, https://doi.org/10.5194/acp-22-4019-2022, 2022
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We present an intercomparison of 2009–2018 lapse rate tropopause characteristics as derived from ECMWF's ERA5 and ERA-Interim reanalyses. Large-scale features are similar, but ERA5 shows notably larger variability, which we mainly attribute to UTLS temperature fluctuations due to gravity waves being better resolved by ECMWF's IFS forecast model. Following evaluation with radiosondes and GPS data, we conclude ERA5 will be a more suitable asset for tropopause-related studies in future work.
Helmut Ziereis, Peter Hoor, Jens-Uwe Grooß, Andreas Zahn, Greta Stratmann, Paul Stock, Michael Lichtenstern, Jens Krause, Vera Bense, Armin Afchine, Christian Rolf, Wolfgang Woiwode, Marleen Braun, Jörn Ungermann, Andreas Marsing, Christiane Voigt, Andreas Engel, Björn-Martin Sinnhuber, and Hermann Oelhaf
Atmos. Chem. Phys., 22, 3631–3654, https://doi.org/10.5194/acp-22-3631-2022, https://doi.org/10.5194/acp-22-3631-2022, 2022
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Airborne observations were conducted in the lowermost Arctic stratosphere during the winter of 2015/2016. The observed distribution of reactive nitrogen shows clear indications of nitrification in mid-winter and denitrification in late winter. This was caused by the formation of polar stratospheric cloud particles, which were observed during several flights. The sedimentation and evaporation of these particles and the descent of air masses cause a redistribution of reactive nitrogen.
Sergey M. Khaykin, Elizabeth Moyer, Martina Krämer, Benjamin Clouser, Silvia Bucci, Bernard Legras, Alexey Lykov, Armin Afchine, Francesco Cairo, Ivan Formanyuk, Valentin Mitev, Renaud Matthey, Christian Rolf, Clare E. Singer, Nicole Spelten, Vasiliy Volkov, Vladimir Yushkov, and Fred Stroh
Atmos. Chem. Phys., 22, 3169–3189, https://doi.org/10.5194/acp-22-3169-2022, https://doi.org/10.5194/acp-22-3169-2022, 2022
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The Asian monsoon anticyclone is the key contributor to the global annual maximum in lower stratospheric water vapour. We investigate the impact of deep convection on the lower stratospheric water using a unique set of observations aboard the high-altitude M55-Geophysica aircraft deployed in Nepal in summer 2017 within the EU StratoClim project. We find that convective plumes of wet air can persist within the Asian anticyclone for weeks, thereby enhancing the occurrence of high-level clouds.
Dina Khordakova, Christian Rolf, Jens-Uwe Grooß, Rolf Müller, Paul Konopka, Andreas Wieser, Martina Krämer, and Martin Riese
Atmos. Chem. Phys., 22, 1059–1079, https://doi.org/10.5194/acp-22-1059-2022, https://doi.org/10.5194/acp-22-1059-2022, 2022
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Extreme storms transport humidity from the troposphere to the stratosphere. Here it has a strong impact on the climate. With ongoing global warming, we expect more storms and, hence, an enhancement of this effect. A case study was performed in order to measure the impact of the direct injection of water vapor into the lower stratosphere. The measurements displayed a significant transport of water vapor into the lower stratosphere, and this was supported by satellite and reanalysis data.
Manuel Baumgartner, Christian Rolf, Jens-Uwe Grooß, Julia Schneider, Tobias Schorr, Ottmar Möhler, Peter Spichtinger, and Martina Krämer
Atmos. Chem. Phys., 22, 65–91, https://doi.org/10.5194/acp-22-65-2022, https://doi.org/10.5194/acp-22-65-2022, 2022
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An important mechanism for the appearance of ice particles in the upper troposphere at low temperatures is homogeneous nucleation. This process is commonly described by the
Koop line, predicting the humidity at freezing. However, laboratory measurements suggest that the freezing humidities are above the Koop line, motivating the present study to investigate the influence of different physical parameterizations on the homogeneous freezing with the help of a detailed numerical model.
Christoph Mahnke, Ralf Weigel, Francesco Cairo, Jean-Paul Vernier, Armin Afchine, Martina Krämer, Valentin Mitev, Renaud Matthey, Silvia Viciani, Francesco D'Amato, Felix Ploeger, Terry Deshler, and Stephan Borrmann
Atmos. Chem. Phys., 21, 15259–15282, https://doi.org/10.5194/acp-21-15259-2021, https://doi.org/10.5194/acp-21-15259-2021, 2021
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In 2017, in situ aerosol measurements were conducted aboard the M55 Geophysica in the Asian monsoon region. The vertical particle mixing ratio profiles show a distinct layer (15–18.5 km), the Asian tropopause aerosol layer (ATAL). The backscatter ratio (BR) was calculated based on the aerosol size distributions and compared with the BRs detected by a backscatter probe and a lidar aboard M55, and by the CALIOP lidar. All four methods show enhanced BRs in the ATAL altitude range (max. at 17.5 km).
Julia Schneider, Kristina Höhler, Robert Wagner, Harald Saathoff, Martin Schnaiter, Tobias Schorr, Isabelle Steinke, Stefan Benz, Manuel Baumgartner, Christian Rolf, Martina Krämer, Thomas Leisner, and Ottmar Möhler
Atmos. Chem. Phys., 21, 14403–14425, https://doi.org/10.5194/acp-21-14403-2021, https://doi.org/10.5194/acp-21-14403-2021, 2021
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Homogeneous freezing is a relevant mechanism for the formation of cirrus clouds in the upper troposphere. Based on an extensive set of homogeneous freezing experiments at the AIDA chamber with aqueous sulfuric acid aerosol, we provide a new fit line for homogeneous freezing onset conditions of sulfuric acid aerosol focusing on cirrus temperatures. In the atmosphere, homogeneous freezing thresholds have important implications on the cirrus cloud occurrence and related cloud radiative effects.
Cited articles
Baumgardner, D., Abel, S. J., Axisa, D., Cotton, R., Crosier, J., Field, P., Gurganus, C., Heymsfield, A., Korolev, A., Krämer, M., Lawson, P., McFarquhar, G., Ulanowski, Z., and Um, J.: Cloud Ice Properties: In Situ Measurement Challenges; Chap. 9 of “Ice Formation and Evolution in Clouds and Precipitation: Measurement and Modeling Challenges”, Meteorol. Monographs, https://doi.org/10.1175/AMSMONOGRAPHS-D-16-0011.1, 2017. a
Baumgartner, M., Rolf, C., Grooß, J.-U., Schneider, J., Schorr, T., Möhler, O., Spichtinger, P., and Krämer, M.: New investigations on homogeneous ice nucleation: the effects of water activity and water saturation formulations, Atmos. Chem. Phys., 22, 65–91, https://doi.org/10.5194/acp-22-65-2022, 2022. a
Bunz, H., Benz, S., Gensch, I., and Krämer, M.: MAID: a model to simulate UT/LS aerosols and ice clouds, Envir. Res. Lett., 3, 035001, https://doi.org/10.1088/1748-9326/3/3/035001, 2008. a
Costa, A., Meyer, J., Afchine, A., Luebke, A., Günther, G., Dorsey, J. R., Gallagher, M. W., Ehrlich, A., Wendisch, M., Baumgardner, D., Wex, H., and Krämer, M.: Classification of Arctic, midlatitude and tropical clouds in the mixed-phase temperature regime, Atmos. Chem. Phys., 17, 12219–12238, https://doi.org/10.5194/acp-17-12219-2017, 2017. a, b, c
Dollner, M., Gasteiger, J., Schöberl, M., Gattringer, A., Beres, N., Bui, T., Diskin, G., and Weinzierl, B.: The Cloud Indicator: A novel algorithm for automatic detection and classification of clouds using airborne in situ observations, Atmospheric Research, 308, 107504, https://doi.org/10.1016/j.atmosres.2024.107504, 2024. a
Field, P. R., Hogan, R. J., Brown, P. R. A., Illingworth, A. J., Choularton, T. W., and Cotton, R. J.: Parametrization of ice-particle size distributions for mid-latitude stratiform cloud, Quarterly Journal of the Royal Meteorological Society, 131, 1997–2017, https://doi.org/10.1256/qj.04.134, 2005. a, b, c
Gallagher, M. W., Connolly, P. J., Whiteway, J., Figueras-Nieto, D., Flynn, M., Choularton, T. W., Bower, K. N., Cook, C., Busen, R., and Hacker, J.: An overview of the microphysical structure of cirrus clouds observed during EMERALD-1, Quarterly Journal of the Royal Meteorological Society, 131, 1143–1169, https://doi.org/10.1256/qj.03.138, 2005. a
Heymsfield, A., Schmitt, C., and Bansemer, A.: Ice Cloud Particle Size Distributions and Pressure-Dependent Terminal Velocities from In Situ Observations at Temperatures from 0C to −86C, Journal Atm. Sci., 20, 4123–4154, https://doi.org/10.1175/JAS-D-12-0124.1, 2013. a, b, c
IPCC: Clouds and Aerosols, in: Climate Change 2013 – The Physical Science Basis: Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, 571–658, https://doi.org/10.1017/CBO9781107415324.016, 2014. a
Jackson, R. C., McFarquhar, G., Fridland, A. M., and Atlas, R.: The dependence of cirrus gamma size distributions expressed as volumes in N0-λ-μ phase space and bulk cloud properties on environmental conditions: Results from the Small Ice Particles in Cirrus Experiment (SPARTICUS), J. Geophys. Res. Atmos., 120, 10351–10377, https://doi.org/10.1002/2015JD023492, 2015. a, b, c
Jensen, E. J., Pfister, L., Bui, T.-P., Lawson, P., and Baumgardner, D.: Ice nucleation and cloud microphysical properties in tropical tropopause layer cirrus, Atmos. Chem. Phys., 10, 1369–1384, https://doi.org/10.5194/acp-10-1369-2010, 2010. a
Jensen, E. J., Kärcher, B., Woods, S., Krämer, M., and Ueyama, R.: The Impact of Gravity Waves on the Evolution of Tropical Anvil Cirrus Microphysical Properties, Journal of Geophysical Research: Atmospheres, 129, e2023JD039887, https://doi.org/10.1029/2023JD039887, 2024. a
Jurkat-Witschas, T., Voigt, C., Groß, S., Kaufmann, S., Sauer, D., De la Torre Castro, E., Krämer, M., Schäfler, A., Afchine, A., Attinger, R., Bartolome Garcia, I., Beer, C. G., Bugliaro, L., Clemen, H.-C., Dekoutsidis, G., Ehrlich, A., Grawe, S., Hahn, V., Hendricks, J., Järvinen, E., Klimach, T., Krüger, K., Krüger, O., Lucke, J., Luebke, A. E., Marsing, A., Mayer, B., Mayer, J., Mertes, S., Moser, M., Müller, H., Nenakhov, V., Pöhlker, M., Pöschl, U., Pörtge, V., Rautenhaus, M., Righi, M., Röttenbacher, J., Rubin-Zuzic, M., Schaefer, J., Schnaiter, M., Schneider, J., Schumann, U., Spelten, N., Stratmann, F., Tomsche, L., Wagner, S., Wang, Z., Weber, A., Wendisch, M., Wernli, H., Wetzel, B., Wirth, M., Zahn, A., Ziereis, H., and Zöger, M.: CIRRUS-HL: Picturing the high- and mid-latitude summer cirrus and contrail cirrus above Europe with airborne measurements aboard the research aircraft HALO, B. Am. Meteorol. Soc., online first, https://doi.org/10.1175/BAMS-D-23-0270.1, 2025. a
Kärcher, B., Hendricks, J., and Lohmann, U.: Physically based parameterization of cirrus cloud formation for use in global atmospheric models, J. Geophys. Res., 111, https://doi.org/10.1029/2005JD006219, 2006. a
Krämer, M., Rolf, C., Luebke, A., Afchine, A., Spelten, N., Costa, A., Meyer, J., Zöger, M., Smith, J., Herman, R. L., Buchholz, B., Ebert, V., Baumgardner, D., Borrmann, S., Klingebiel, M., and Avallone, L.: A microphysics guide to cirrus clouds – Part 1: Cirrus types, Atmos. Chem. Phys., 16, 3463–3483, https://doi.org/10.5194/acp-16-3463-2016, 2016. a, b, c, d, e, f, g, h, i, j, k
Krämer, M., Rolf, C., Spelten, N., Afchine, A., Fahey, D., Jensen, E., Khaykin, S., Kuhn, T., Lawson, P., Lykov, A., Pan, L. L., Riese, M., Rollins, A., Stroh, F., Thornberry, T., Wolf, V., Woods, S., Spichtinger, P., Quaas, J., and Sourdeval, O.: A microphysics guide to cirrus – Part 2: Climatologies of clouds and humidity from observations, Atmos. Chem. Phys., 20, 12569–12608, https://doi.org/10.5194/acp-20-12569-2020, 2020. a, b, c, d, e, f, g, h, i, j, k
Krämer, M., Rolf, C., Afchine, A., and Spelten, N.: The Cirrus Guide III Data Set, B2SHARE-EUDAT [data set], https://doi.org/10.34730/9EF25DADB84F4E7D9E0281CCB40 86A3B, 2025. a
Lawson, R. P., Woods, S., Jensen, E., Erfani, E., Gurganus, C., Gallagher, M., Connolly, P., Whiteway, J., Baran, A. J., May, P., Heymsfield, A., Schmitt, C. G., McFarquhar, G., Um, J., Protat, A., Bailey, M., Lance, S., Muehlbauer, A., Stith, J., Korolev, A., Toon, O. B., and Krämer, M.: A Review of Ice Particle Shapes in Cirrus formed In Situ and in Anvils, Journal of Geophysical Research: Atmospheres, 124, 10049–10090, https://doi.org/10.1029/2018JD030122, 2019. a, b
Li, Y., Mahnke, C., Rohs, S., Bundke, U., Spelten, N., Dekoutsidis, G., Groß, S., Voigt, C., Schumann, U., Petzold, A., and Krämer, M.: Upper-tropospheric slightly ice-subsaturated regions: frequency of occurrence and statistical evidence for the appearance of contrail cirrus, Atmos. Chem. Phys., 23, 2251–2271, https://doi.org/10.5194/acp-23-2251-2023, 2023. a, b, c, d
Luebke, A. E., Afchine, A., Costa, A., Grooß, J.-U., Meyer, J., Rolf, C., Spelten, N., Avallone, L. M., Baumgardner, D., and Krämer, M.: The origin of midlatitude ice clouds and the resulting influence on their microphysical properties, Atmos. Chem. Phys., 16, 5793–5809, https://doi.org/10.5194/acp-16-5793-2016, 2016. a
Rolf, C., Krämer, M., Schiller, C., Hildebrandt, M., and Riese, M.: Lidar observation and model simulation of a volcanic-ash-induced cirrus cloud during the Eyjafjallajökull eruption, Atmos. Chem. Phys., 12, 10281–10294, https://doi.org/10.5194/acp-12-10281-2012, 2012. a
Sölch, I. and Kärcher, B.: A large-eddy model for cirrus clouds with explicit aerosol and ice microphysics and Lagrangian ice particle tracking, Quarterly Journal of the Royal Meteorological Society, 136, 2074–2093, https://doi.org/10.1002/qj.689, 2010. a, b
Spichtinger, P. and Gierens, K. M.: Modelling of cirrus clouds – Part 1a: Model description and validation, Atmos. Chem. Phys., 9, 685–706, https://doi.org/10.5194/acp-9-685-2009, 2009. a
Wang, Y., Su, H., Jiang, J. H., Xu, F., and Yung, Y. L.: Impact of Cloud Ice Particle Size Uncertainty in a Climate Model and Implications for Future Satellite Missions, Journal of Geophysical Research: Atmospheres, 125, e2019JD032119, https://doi.org/10.1029/2019JD032119, 2020. a
Wolf, V., Kuhn, T., Milz, M., Voelger, P., Krämer, M., and Rolf, C.: Arctic ice clouds over northern Sweden: microphysical properties studied with the Balloon-borne Ice Cloud particle Imager B-ICI, Atmos. Chem. Phys., 18, 17371–17386, https://doi.org/10.5194/acp-18-17371-2018, 2018. a
Short summary
The size and number of cirrus ice crystals is one parameter influencing the still uncertain effect of cirrus clouds on climate. Here, the occurrence of ice particle sizes and concentrations with varying temperature and cloud microphysical thickness is analyzed as well as whether they formed in-situ or were transported upwards as frozen droplets from further below. The analyses are based on a large database of airborne measurements and extensive simulations.
The size and number of cirrus ice crystals is one parameter influencing the still uncertain...
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