Hypothesis:

The cloud formation in the initial state of CAOs impacts the downstream evolution of cloud morphology, precipitation, and cloud radiative effects.

For testing this hypothesis the work in phase III aims to answer the questions:

• How and when do transitions of cloud regimes occur in CAOs, vary regionally, and change with Arctic warming?
• Do clouds over sea ice precondition the development of clouds in CAOs?
• What are the effects of the air mass transitions on precipitation and cloud radiative forcing?

The project will contribute to the overarching Strategic Questions SQ1 and SQ2 with respect to CAOs. The evolution of boundary layer clouds and their radiative effects in CAOs will be characterized depending on the conditions over the MIZ. Due to Arctic warming (less colder air masses, more variable sea ice edge), this cloud evolution might experience changes. Quantifying the cloud radiative effects for different initial conditions will indicate, whether changes in the characteristics of CAOs will amplify the Arctic warming or not.

Achievements phase II

• A comprehensive data set has been generated through a series of (AC)³ airborne campaigns highlighting the variability of cloud properties through different seasons, weather conditions and over different surfaces (sea ice, open ocean).
• The variability of cloud fractions among the campaigns is mostly driven by the origin of air masses.
• In early summer, liquid-phase clouds have a larger effective radius, optical thickness and liquid water path compared to spring conditions.
• Larger cloud droplets and slightly reduced liquid water contents were observed over the ice-free ocean compared to sea ice, mainly driven by the surface temperature and convection processes.
• Cloud radar measurements reveal the dominance of hydrometeor fraction below 1.5 km. Satellite observations by CloudSat overestimate this occurrence by more than 30 % especially during CAOs.

Achievements phase I

Within B03, Arctic mixed–phase clouds were observed with a set of unique remote sensing (Mech et al., 2019) and in–situ instruments during ACLOUD (Wendisch et al., 2019) and AFLUX. A comprehensive characterisation of the horizontal and vertical variability of cloud properties was performed. Ambient and cloud forming aerosol particles were separated and analysed for their physical and chemical properties. Surprisingly, mixed–phase clouds and precipitating snow were frequently observed in a rather high temperature range between –13 ◦C and 0 ◦C. It was shown, that the vertical distribution of ice particles in clouds differs in cold and warm air masses (Knudsen et al., 2018a). Also, the in–situ observations identified larger cloud particle residuals over open ocean and smaller over sea ice, which indicates different pathways of cloud forming particles into the cloud: below-cloud mixing of large sea salt dominated over the open ocean and cloud top entrainment of smaller tropospheric particles over closed sea ice (Wendisch et al., 2019).

Role within (AC)³

Project Posters

Phase III Evaluation poster 2023	Phase II Evaluation poster 2019	Phase I Evaluation poster 2015

Project Members

Publications

2026

2025

Müller, J. J., Schäfer, M., Rosenburg, S., Ehrlich, A., and Wendisch, M. , September 2025: High-resolution maps of Arctic surface skin temperature and type retrieved from airborne thermal infrared imagery collected during the HALO-(AC)³ campaign. Atmospheric Meas. Tech., 18(18):4695–4708, doi:10.5194/amt-18-4695-2025

Klingebiel, M., Ehrlich, A., Gryschka, M., Risse, N., Maherndl, N., Schirmacher, I., Rosenburg, S., Hörnig, S., Moser, M., Jäkel, E., Schäfer, M., Deneke, H., Mech, M., Voigt, C., and Wendisch, M. , September 2025: Airborne observations of cloud properties during their evolution from organized streets to isotropic cloud structures along an Arctic cold-air outbreak. Atmospheric Chem. Phys., 25(17):9787–9801, doi:10.5194/acp-25-9787-2025

Ebell, K., Buhren, C., Gierens, R., Chellini, G., Lauer, M., Walbröl, A., Dahlke, S., Krobot, P., and Mech, M. , July 2025: Impact of weather systems on observed precipitation at Ny-Ålesund (Svalbard). Atmospheric Chem. Phys., 25(13):7315–7342, doi:10.5194/acp-25-7315-2025

Dorff, H., Ewald, F., Konow, H., Mech, M., Ori, D., Schemann, V., Walbröl, A., Wendisch, M., and Ament, F. , 2025: Moisture budget estimates derived from airborne observations in an Arctic atmospheric river during its dissipation. Atmos. Chem. Phys., 25(14):8329–8354, doi:10.5194/acp-25-8329-2025

Wendisch, M., Kirbus, B., Ori, D., Shupe, M. D., Crewell, S., Sodemann, H., and Schemann, V. , 2025: Observed and modeled Arctic airmass transformations during warm air intrusions and cold air outbreaks. Atmos. Chem. Phys., 25(21):15047–15076, doi:10.5194/acp-25-15047-2025

2024

Walbröl, A., Griesche, H. J., Mech, M., Crewell, S., and Ebell, K. , October 2024: Combining Low- and High-Frequency Microwave Radiometer Measurements from the MOSAiC Expedition for Enhanced Water Vapour Products. Atmospheric Meas. Tech., 17(20):6223–6245, doi:10.5194/amt-17-6223-2024

Risse, N., Mech, M., Prigent, C., Spreen, G., and Crewell, S. , September 2024: Assessing Sea Ice Microwave Emissivity up to Submillimeter Waves from Airborne and Satellite Observations. The Cryosphere, 18(9):4137–4163, doi:10.5194/tc-18-4137-2024

Arteaga, D., Planche, C., Tridon, F., Dupuy, R., Baudoux, A., Banson, S., Baray, J., Mioche, G., Ehrlich, A., Mech, M., Mertes, S., Wendisch, M., Wobrock, W., and Jourdan, O. , September 2024: Arctic Mixed-Phase Clouds Simulated by the WRF Model: Comparisons with ACLOUD Radar and in Situ Airborne Observations and Sensitivity of Microphysics Properties. Atmospheric Res., 307:107471, doi:10.1016/j.atmosres.2024.107471

Wendisch, M., Crewell, S., Ehrlich, A., Herber, A., Kirbus, B., Lüpkes, C., Mech, M., Abel, S. J., Akansu, E. F., Ament, F., Aubry, C., Becker, S., Borrmann, S., Bozem, H., Brückner, M., Clemen, H., Dahlke, S., Dekoutsidis, G., Delanoë, J., De La Torre Castro, E., Dorff, H., Dupuy, R., Eppers, O., Ewald, F., George, G., Gorodetskaya, I. V., Grawe, S., Groß, S., Hartmann, J., Henning, S., Hirsch, L., Jäkel, E., Joppe, P., Jourdan, O., Jurányi, Z., Karalis, M., Kellermann, M., Klingebiel, M., Lonardi, M., Lucke, J., Luebke, A. E., Maahn, M., Maherndl, N., Maturilli, M., Mayer, B., Mayer, J., Mertes, S., Michaelis, J., Michalkov, M., Mioche, G., Moser, M., Müller, H., Neggers, R., Ori, D., Paul, D., Paulus, F. M., Pilz, C., Pithan, F., Pöhlker, M., Pörtge, V., Ringel, M., Risse, N., Roberts, G. C., Rosenburg, S., Röttenbacher, J., Rückert, J., Schäfer, M., Schaefer, J., Schemann, V., Schirmacher, I., Schmidt, J., Schmidt, S., Schneider, J., Schnitt, S., Schwarz, A., Siebert, H., Sodemann, H., Sperzel, T., Spreen, G., Stevens, B., Stratmann, F., Svensson, G., Tatzelt, C., Tuch, T., Vihma, T., Voigt, C., Volkmer, L., Walbröl, A., Weber, A., Wehner, B., Wetzel, B., Wirth, M., and Zinner, T. , August 2024: Overview: Quasi-Lagrangian Observations of Arctic Air Mass Transformations – Introduction and Initial Results of the HALO–(A C)\textsuperscript3 Aircraft Campaign. Atmospheric Chem. Phys., 24(15):8865–8892, doi:10.5194/acp-24-8865-2024

Walbröl, A., Michaelis, J., Becker, S., Dorff, H., Ebell, K., Gorodetskaya, I., Heinold, B., Kirbus, B., Lauer, M., Maherndl, N., Maturilli, M., Mayer, J., Müller, H., Neggers, R. A. J., Paulus, F. M., Röttenbacher, J., Rückert, J. E., Schirmacher, I., Slättberg, N., Ehrlich, A., Wendisch, M., and Crewell, S. , July 2024: Contrasting Extremely Warm and Long-Lasting Cold Air Anomalies in the North Atlantic Sector of the Arctic during the HALO-(A C)\textsuperscript3 Campaign. Atmospheric Chem. Phys., 24(13):8007–8029, doi:10.5194/acp-24-8007-2024

Röttenbacher, J., Ehrlich, A., Müller, H., Ewald, F., Luebke, A. E., Kirbus, B., Hogan, R. J., and Wendisch, M. , July 2024: Evaluating the Representation of Arctic Cirrus Solar Radiative Effects in the Integrated Forecasting System with Airborne Measurements. Atmospheric Chem. Phys., 24(14):8085–8104, doi:10.5194/acp-24-8085-2024

Schirmacher, I., Schnitt, S., Klingebiel, M., Maherndl, N., Kirbus, B., Ehrlich, A., Mech, M., and Crewell, S. Clouds and Precipitation in the Initial Phase of Marine Cold Air Outbreaks as Observed by Airborne Remote Sensing. April 2024. doi:10.5194/egusphere-2024-850.

Müller, H., Ehrlich, A., Jäkel, E., Röttenbacher, J., Kirbus, B., Schäfer, M., Hogan, R. J., and Wendisch, M. , April 2024: Evaluation of Downward and Upward Solar Irradiances Simulated by the Integrated Forecasting System of ECMWF Using Airborne Observations above Arctic Low-Level Clouds. Atmospheric Chem. Phys., 24(7):4157–4175, doi:10.5194/acp-24-4157-2024

Kirbus, B., Schirmacher, I., Klingebiel, M., Schäfer, M., Ehrlich, A., Slättberg, N., Lucke, J., Moser, M., Müller, H., and Wendisch, M. , April 2024: Thermodynamic and Cloud Evolution in a Cold-Air Outbreak during HALO-(AC)\textsuperscript3 : Quasi-Lagrangian Observations Compared to the ERA5 and CARRA Reanalyses. Atmospheric Chem. Phys., 24(6):3883–3904, doi:10.5194/acp-24-3883-2024

2023

Klingebiel, M., Ehrlich, A., Ruiz-Donoso, E., Risse, N., Schirmacher, I., Jäkel, E., Schäfer, M., Wolf, K., Mech, M., Moser, M., Voigt, C., and Wendisch, M. , December 2023: Variability and Properties of Liquid-Dominated Clouds over the Ice-Free and Sea-Ice-Covered Arctic Ocean. Atmospheric Chem. Phys., 23(24):15289–15304, doi:10.5194/acp-23-15289-2023

Schirmacher, I., Kollias, P., Lamer, K., Mech, M., Pfitzenmaier, L., Wendisch, M., and Crewell, S. , September 2023: Assessing Arctic Low-Level Clouds and Precipitation from above – a Radar Perspective. Atmospheric Meas. Tech., 16(17):4081–4100, doi:10.5194/amt-16-4081-2023

Rosenburg, S., Lange, C., Jäkel, E., Schäfer, M., Ehrlich, A., and Wendisch, M. , August 2023: Retrieval of Snow Layer and Melt Pond Properties on Arctic Sea Ice from Airborne Imaging Spectrometer Observations. Atmospheric Meas. Tech., 16(16):3915–3930, doi:10.5194/amt-16-3915-2023

Zanatta, M., Mertes, S., Jourdan, O., Dupuy, R., Järvinen, E., Schnaiter, M., Eppers, O., Schneider, J., Jurányi, Z., and Herber, A. , July 2023: Airborne Investigation of Black Carbon Interaction with Low-Level, Persistent, Mixed-Phase Clouds in the Arctic Summer. Atmospheric Chem. Phys., 23(14):7955–7973, doi:10.5194/acp-23-7955-2023

Moser, M., Voigt, C., Jurkat-Witschas, T., Hahn, V., Mioche, G., Jourdan, O., Dupuy, R., Gourbeyre, C., Schwarzenboeck, A., Lucke, J., Boose, Y., Mech, M., Borrmann, S., Ehrlich, A., Herber, A., Lüpkes, C., and Wendisch, M. , July 2023: Microphysical and Thermodynamic Phase Analyses of Arctic Low-Level Clouds Measured above the Sea Ice and the Open Ocean in Spring and Summer. Atmospheric Chem. Phys., 23(13):7257–7280, doi:10.5194/acp-23-7257-2023

Chylik, J., Chechin, D., Dupuy, R., Kulla, B. S., Lüpkes, C., Mertes, S., Mech, M., and Neggers, R. A. J. , April 2023: Aerosol Impacts on the Entrainment Efficiency of Arctic Mixed-Phase Convection in a Simulated Air Mass over Open Water. Atmospheric Chem. Phys., 23(8):4903–4929, doi:10.5194/acp-23-4903-2023

Ehrlich, A., Zöger, M., Giez, A., Nenakhov, V., Mallaun, C., Maser, R., Röschenthaler, T., Luebke, A. E., Wolf, K., Stevens, B., and Wendisch, M. , March 2023: A New Airborne Broadband Radiometer System and an Efficient Method to Correct Dynamic Thermal Offsets. Atmospheric Meas. Tech., 16(6):1563–1581, doi:10.5194/amt-16-1563-2023

2022

Mech, M., Ehrlich, A., Herber, A., Lüpkes, C., Wendisch, M., Becker, S., Boose, Y., Chechin, D., Crewell, S., Dupuy, R., Gourbeyre, C., Hartmann, J., Jäkel, E., Jourdan, O., Kliesch, L., Klingebiel, M., Kulla, B. S., Mioche, G., Moser, M., Risse, N., Ruiz-Donoso, E., Schäfer, M., Stapf, J., and Voigt, C. , December 2022: MOSAiC-ACA and AFLUX - Arctic Airborne Campaigns Characterizing the Exit Area of MOSAiC. Sci. Data, 9(1):790, doi:10.1038/s41597-022-01900-7

Schäfer, M., Wolf, K., Ehrlich, A., Hallbauer, C., Jäkel, E., Jansen, F., Luebke, A. E., Müller, J., Thoböll, J., Röschenthaler, T., Stevens, B., and Wendisch, M. , March 2022: VELOX – a New Thermal Infrared Imager for Airborne Remote Sensing of Cloud and Surface Properties. Atmospheric Meas. Tech., 15(5):1491–1509, doi:10.5194/amt-15-1491-2022

Shupe, M. D., Rex, M., Blomquist, B., Persson, P. O. G., Schmale, J., Uttal, T., Althausen, D., Angot, H., Archer, S., Bariteau, L., Beck, I., Bilberry, J., Bucci, S., Buck, C., Boyer, M., Brasseur, Z., Brooks, I. M., Calmer, R., Cassano, J., Castro, V., Chu, D., Costa, D., Cox, C. J., Creamean, J., Crewell, S., Dahlke, S., Damm, E., De Boer, G., Deckelmann, H., Dethloff, K., Dütsch, M., Ebell, K., Ehrlich, A., Ellis, J., Engelmann, R., Fong, A. A., Frey, M. M., Gallagher, M. R., Ganzeveld, L., Gradinger, R., Graeser, J., Greenamyer, V., Griesche, H., Griffiths, S., Hamilton, J., Heinemann, G., Helmig, D., Herber, A., Heuzé, C., Hofer, J., Houchens, T., Howard, D., Inoue, J., Jacobi, H., Jaiser, R., Jokinen, T., Jourdan, O., Jozef, G., King, W., Kirchgaessner, A., Klingebiel, M., Krassovski, M., Krumpen, T., Lampert, A., Landing, W., Laurila, T., Lawrence, D., Lonardi, M., Loose, B., Lüpkes, C., Maahn, M., Macke, A., Maslowski, W., Marsay, C., Maturilli, M., Mech, M., Morris, S., Moser, M., Nicolaus, M., Ortega, P., Osborn, J., Pätzold, F., Perovich, D. K., Petäjä, T., Pilz, C., Pirazzini, R., Posman, K., Powers, H., Pratt, K. A., Preußer, A., Quéléver, L., Radenz, M., Rabe, B., Rinke, A., Sachs, T., Schulz, A., Siebert, H., Silva, T., Solomon, A., Sommerfeld, A., Spreen, G., Stephens, M., Stohl, A., Svensson, G., Uin, J., Viegas, J., Voigt, C., Von Der Gathen, P., Wehner, B., Welker, J. M., Wendisch, M., Werner, M., Xie, Z., and Yue, F. , February 2022: Overview of the MOSAiC Expedition: Atmosphere. Elem Sci Anth, 10(1):00060, doi:10.1525/elementa.2021.00060

2021

Kwiezinski, C., Weller, C., Van Pinxteren, D., Brüggemann, M., Mertes, S., Stratmann, F., and Herrmann, H. , June 2021: Determination of Highly Polar Compounds in Atmospheric Aerosol Particles at Ultra-trace Levels Using Ion Chromatography Orbitrap Mass Spectrometry. J. Sep. Sci., 44(12):2343–2357, doi:10.1002/jssc.202001048

2020

Mech, M., Maahn, M., Kneifel, S., Ori, D., Orlandi, E., Kollias, P., Schemann, V., and Crewell, S. , September 2020: PAMTRA 1.0: The Passive and Active Microwave Radiative TRAnsfer Tool for Simulating Radiometer and Radar Measurements of the Cloudy Atmosphere. Geosci. Model Dev., 13(9):4229–4251, doi:10.5194/gmd-13-4229-2020

Ruiz-Donoso, E., Ehrlich, A., Schäfer, M., Jäkel, E., Schemann, V., Crewell, S., Mech, M., Kulla, B. S., Kliesch, L., Neuber, R., and Wendisch, M. , May 2020: Small-Scale Structure of Thermodynamic Phase in Arctic Mixed-Phase Clouds Observed by Airborne Remote Sensing during a Cold Air Outbreak and a Warm Air Advection Event. Atmospheric Chem. Phys., 20(9):5487–5511, doi:10.5194/acp-20-5487-2020

2019

Ehrlich, A., Wendisch, M., Lüpkes, C., Buschmann, M., Bozem, H., Chechin, D., Clemen, H., Dupuy, R., Eppers, O., Hartmann, J., Herber, A., Jäkel, E., Järvinen, E., Jourdan, O., Kästner, U., Kliesch, L., Köllner, F., Mech, M., Mertes, S., Neuber, R., Ruiz-Donoso, E., Schnaiter, M., Schneider, J., Stapf, J., and Zanatta, M. , November 2019: A Comprehensive in Situ and Remote Sensing Data Set from the Arctic CLoud Observations Using Airborne Measurements during Polar Day (ACLOUD) Campaign. Earth Syst. Sci. Data, 11(4):1853–1881, doi:10.5194/essd-11-1853-2019

Mech, M., Kliesch, L., Anhäuser, A., Rose, T., Kollias, P., and Crewell, S. , September 2019: Microwave Radar/Radiometer for Arctic Clouds (MiRAC): First Insights from the ACLOUD Campaign. Atmospheric Meas. Tech., 12(9):5019–5037, doi:10.5194/amt-12-5019-2019

Wendisch, M., Macke, A., Ehrlich, A., Lüpkes, C., Mech, M., Chechin, D., Dethloff, K., Velasco, C. B., Bozem, H., Brückner, M., Clemen, H., Crewell, S., Donth, T., Dupuy, R., Ebell, K., Egerer, U., Engelmann, R., Engler, C., Eppers, O., Gehrmann, M., Gong, X., Gottschalk, M., Gourbeyre, C., Griesche, H., Hartmann, J., Hartmann, M., Heinold, B., Herber, A., Herrmann, H., Heygster, G., Hoor, P., Jafariserajehlou, S., Jäkel, E., Järvinen, E., Jourdan, O., Kästner, U., Kecorius, S., Knudsen, E. M., Köllner, F., Kretzschmar, J., Lelli, L., Leroy, D., Maturilli, M., Mei, L., Mertes, S., Mioche, G., Neuber, R., Nicolaus, M., Nomokonova, T., Notholt, J., Palm, M., Van Pinxteren, M., Quaas, J., Richter, P., Ruiz-Donoso, E., Schäfer, M., Schmieder, K., Schnaiter, M., Schneider, J., Schwarzenböck, A., Seifert, P., Shupe, M. D., Siebert, H., Spreen, G., Stapf, J., Stratmann, F., Vogl, T., Welti, A., Wex, H., Wiedensohler, A., Zanatta, M., and Zeppenfeld, S. , May 2019: The Arctic Cloud Puzzle: Using ACLOUD/PASCAL Multiplatform Observations to Unravel the Role of Clouds and Aerosol Particles in Arctic Amplification. Bull. Am. Meteorol. Soc., 100(5):841–871, doi:10.1175/BAMS-D-18-0072.1

2018

Knudsen, E. M., Heinold, B., Dahlke, S., Bozem, H., Crewell, S., Gorodetskaya, I. V., Heygster, G., Kunkel, D., Maturilli, M., Mech, M., Viceto, C., Rinke, A., Schmithüsen, H., Ehrlich, A., Macke, A., Lüpkes, C., and Wendisch, M. , December 2018: Meteorological Conditions during the ACLOUD/PASCAL Field Campaign near Svalbard in Early Summer 2017. Atmospheric Chem. Phys., 18(24):17995–18022, doi:10.5194/acp-18-17995-2018

Schäfer, M., Loewe, K., Ehrlich, A., Hoose, C., and Wendisch, M. , September 2018: Simulated and Observed Horizontal Inhomogeneities of Optical Thickness of Arctic Stratus. Atmospheric Chem. Phys., 18(17):13115–13133, doi:10.5194/acp-18-13115-2018

2017

Ehrlich, A., Bierwirth, E., Istomina, L., and Wendisch, M. , September 2017: Combined Retrieval of Arctic Liquid Water Cloud and Surface Snow Properties Using Airborne Spectral Solar Remote Sensing. Atmospheric Meas. Tech., 10(9):3215–3230, doi:10.5194/amt-10-3215-2017

Schäfer, M., Bierwirth, E., Ehrlich, A., Jäkel, E., Werner, F., and Wendisch, M. , February 2017: Directional, Horizontal Inhomogeneities of Cloud Optical Thickness Fields Retrieved from Ground-Based and Airbornespectral Imaging. Atmospheric Chem. Phys., 17(3):2359–2372, doi:10.5194/acp-17-2359-2017

Wendisch, M., Brückner, M., Burrows, J., Crewell, S., Dethloff, K., Ebell, K., Lüpkes, C., Macke, A., Notholt, J., Quaas, J., Rinke, A., and Tegen, I. , January 2017: Understanding Causes and Effects of Rapid Warming in the Arctic. Eos, doi:10.1029/2017EO064803

Korolev, A., McFarquhar, G., Field, P. R., Franklin, C., Lawson, P., Wang, Z., Williams, E., Abel, S. J., Axisa, D., Borrmann, S., Crosier, J., Fugal, J., Krämer, M., Lohmann, U., Schlenczek, O., Schnaiter, M., and Wendisch, M. , January 2017: Mixed-Phase Clouds: Progress and Challenges. Meteorol. Monogr., 58:5.1–5.50, doi:10.1175/AMSMONOGRAPHS-D-17-0001.1

Cziczo, D. J., Ladino, L., Boose, Y., Kanji, Z. A., Kupiszewski, P., Lance, S., Mertes, S., and Wex, H. , January 2017: Measurements of Ice Nucleating Particles and Ice Residuals. Meteorol. Monogr., 58:8.1–8.13, doi:10.1175/AMSMONOGRAPHS-D-16-0008.1

Schäfer, M., Bierwirth, E., Ehrlich, A., Jäkel, E., Werner, F., and Wendisch, M. Cloud Optical Thickness Retrieved from Horizontal Fields of Reflected Solar Spectral Radiance Measured with AisaEAGLE during VERDI Campaign 2012. 2017. doi:10.1594/PANGAEA.874798.

Ehrlich, A., Bierwirth, E., Istomina, L., and Wendisch, M. Cloud Optical Thickness, Cloud Particle Effective Radius, and Effective Snow Grain Size Retrieved from Airborne Spectral Reflectivity Measurements during VERDI 2012 over the Beaufort Sea. 2017. doi:10.1594/PANGAEA.882979.

2016