For many years, TROPOS has participated in national and international cloud field measurement campaigns, which are part of research projects to investigate aerosol-cloud interactions in pure ice clouds (cirrus, contrails) or mixed-phase clouds in temperate latitudes or in the Arctic. The objectives of these field experiments are:

  • Determination of the chemical and microphysical properties of ice particle residues (IPR)
  • Comparison of microphysical and chemical properties of ice particle residues with aerosol particles identified as Ice Nuceating Particles (INP) in ice nuclei counters
  • Assessment of the atmospheric relevance of certain aerosol particle types with respect to heterogeneous ice formation in atmospheric clouds, e.g. for processstudies in laboratory experiments
  • Provision of input and validation parameters for cloud microphysical models

The experimental in-situ cloud investigations are carried out both on the ground (i.e. mainly at mountain measurement stations) and aircraft-borne. The ice particles are collected by a counterflow virtual impactor (CVI). After drying of the ice particles in the airborne state within the CVI, their ice residuals are analyzed microphysically (number, size, morphology) and chemically (composition, mixing state) also in cooperation with working groups of other research institutes. Current research projects in which atmospheric mixed-phase and ice clouds are investigated are INUIT and ML-CIRRUS.


  • Ice-CVI inlet (right) at the Jungfraujoch research station in the Swiss Alps, Source: Stephan Mertes/TROPOS

  • project logo

  • Mixed-phase cloud over the Aletsch glacier shortly before reaching the Jungfraujoch research station, Source: Stephan Mertes/TROPOS

INUIT: Jungfraujoch, Switzerland, ground-based (2004-2007, 2013, 2017)

A few years ago, TROPOS developed a unique inlet for ground-based collection of small ice particles in mixed-phase clouds, the so-called Ice-CVI. This inlet is specially designed for the highest European research station Jungfraujoch, where the probability of the occurrence of mixed-phase clouds is highest in the winter months. There, TROPOS participated with the Ice-CVI in the 2017 INUIT (Ice Nuclei research UnIT) cloud field measurement campaign, among others. In the most recent, just accepted publication (Lacher et al., 2021) it could be shown that mixed-phase clouds in which the residual concentration and the proportion of residuals with diameters smaller than 100 nm are significantly increased can be interpreted as clouds with higher secondary ice formation.

This project is funded by the German Research Foundation (DFG Research Group 1525, project number 170852269).



  • The HALO research aircraft with the HALO-CVI inlet installed on the lower fuselage during CIRRUS-HL, Source: Andreas Minikin/DLR-FX

  • HALO logo

  • The HALO-CVI inlet on the lower fuselage of HALO during CIRRUS-HL, Source: Stephan Mertes/TROPOS


CIRRUS-HL: North and Central Europe, airborne (2021)

The scientific objectives of the CIRRUS_HL mission are to study the formation and evolution of natural and aviation influenced cirrus clouds in mid and mainly high latitudes. For this purpose, cirrus clouds were measured in flight corridors but also in clean air masses. The measurements took place from May to July 2021 with the German research aircraft HALO over Western, Central and Northern Europe. The residuals of the cirrus ice particles were analysed chemically and microphysically using the HALO-CVI inlet developed at TROPOS. First evaluations of these measurements showed that the concentration of the collected residuals and the collected ice water content are significantly higher also in Arctic cirrus that form from rising mixed phase clouds (liquid phase origin cirrus) than in those that form directly in the ice phase (in-situ cirrus). These results are consistent with the direct ice particle measurements on HALO.

This project was funded by the German Research Foundation (DFG Priority Programme 1294, project numbers 48902976 and 442648163).




Literature on INUIT:

Mertes, S., B. Verheggen, S. Walter, P. Conolly, M. Ebert, J. Schneider, K. N. Bower, J. Cozic, S. Weinbruch, U. Baltensperger and E. Weingartner (2007), Counterflow virtual impactor based collection of small ice particles in mixed-phase clouds for the physico-chemical characterization of tropospheric ice nuclei: Sampler description and first case study, Aerosol Sci. Technol.41(9): 848-864, DOI: doi:10.1080/02786820701501881

Verheggen, B., J. Cozic, E. Weingartner, K. N. Bower, S. Mertes, P. Connolly, M. Gallagher, M. Flynn, T. W. Choularton and U. Baltensperger (2007), Aerosol partitioning beween the interstitial and the condensed phase in mixed-phase clouds, J. Geophys. Res. - Atmos.112(D23): D23202, DOI: doi:10.1029/2007JD008714

Cozic, J., B. Verheggen, S. Mertes, P. Connolly, K. N. Bower, A. Petzold, U. Baltensperger and E. Weingartner (2007), Scavenging of black carbon in mixed phase clouds at the high alpine site Jungfraujoch, Atmos. Chem. Phys.7: 1797-1807

Cozic, J., S. Mertes, B. Verheggen, D. J. Cziczo, S. J. Gallavardin, S. Walter, U. Baltensperger and E. Weingartner (2008), Black carbon enrichment in atmospheric ice particle residuals observed in lower tropospheric mixed phase clouds, J. Geophys. Res. - Atmos.113(D15): D15209, DOI: doi:10.1029/2007JD009266

Cziczo, D. J., O. Stetzer, A. Worringen, M. Ebert, M. Kamphus, J. Curtius, S. Mertes, O. Möhler and U. Lohmann (2009), Inadvertent climate modification due to anthropogenic lead, Nat. Geosci.2(5): 333-336, DOI: doi:10.1038/ngeo499

Kamphus, M., M. Ettner-Mahl, T. Klimach, F. Drewnick, L. Keller, D. J. Cziczo, S. Mertes, S. Borrmann and J. Curtius (2010), Chemical composition of ambient aerosol, ice residues and cloud droplet residues in mixed-phase clouds: Single particle analysis during the Cloud and Aerosol Characterization Experiment (CLACE 6), Atmos. Chem. Phys.10(16): 8077-8095, DOI: doi:10.5194/acp-10-8077-2010

Ebert, M., A. Worringen, N. Benker, S. Mertes, E. Weingartner and S. Weinbruch (2011), Chemical composition and mixing-state of ice residuals sampled within mixed phase clouds, Atmos. Chem. Phys.11: 1-12, DOI: doi:10.5194/acp-11-2805-2011

Kupiszewski, P., E. Weingartner, P. Vochezer, M. Schnaiter, A. Bigi, M. Gysel, B. Rosati, E. Toprak, S. Mertes and U. Baltensperger (2015), The Ice Selective Inlet: a novel technique for exclusive extraction of pristine ice crystals in mixed-phase clouds, Atmos. Meas. Tech.8: 3087-3106, DOI: doi:10.5194/amt-8-3087-2015

Worringen, A., K. Kandler, N. Benker, T. Dirsch, S. Mertes, L. Schenk, U. Kästner, F. Frank, B. Nillius, U. Bundke, D. Rose, J. Curtius, P. Kupiszewski, E. Weingartner, P. Vochezer, J. Schneider, S. Schmidt, S. Weinbruch and M. Ebert (2015), Single-particle characterization of ice-nucleating particles and ice particle residuals sampled by three different techniques, Atmos. Chem. Phys.15: 4161-4178, DOI: doi:10.5194/acp-15-4161-2015

Kupiszewski, P., M. Zanatta, S. Mertes, P. Vochezer, G. Lloyd, J. Schneider, L. Schenk, M. Schnaiter, U. Baltensperger, E. Weingartner and M. Gysel (2016), Ice residual properties in mixed-phase clouds at the high-alpine Jungfraujoch site, J. Geophys. Res. - Atmos.121(20): 12343-12362, DOI: doi:10.1002/2016JD024894

Schmidt, S., J. Schneider, T. Klimach, S. Mertes, L. P. Schenk, P. Kupiszewski, J. Curtius and S. Borrmann (2017), Online single particle analysis of ice particle residuals from mountain-top mixed-phase clouds using laboratory derived particle type assignment, Atmos. Chem. Phys.17(1): 575-594, DOI: doi:10.5194/acp-17-575-2017

Hammer, S. E., S. Mertes, J. Schneider, M. Ebert, K. Kandler and S. Weinbruch (2018), Composition of ice particle residuals in mixed-phase clouds at Jungfraujoch (Switzerland): Enrichment and depletion of particle groups relative to total aerosol Atmos. Chem. Phys.18(19): 13987-14003, DOI: doi:10.5194/acp-18-13987-2018


Literature on ML-CIRRUS:

Voigt, C., U. Schumann, A. Minikin, A. Abdelmonem, A. Afchine, S. Borrmann, M. Boettcher, B. Buchholz, L. Bugliaro, A. Costa, J. Curtius, M. Dollner, A. Dörnbrack, V. Dreiling, V. Ebert , A. Ehrlich, A. Fix, L. Forster, F. Frank, D. Fütterer, A. Giez, K. Graf, J.-U. Grooß, S. Groß, K. Heimerl, B. Heinold, T. Hüneke, E. Järvinen, T. Jurkat, S. Kaufmann, M. Kenntner, M. Klingebiel, T. Klimach, R. Kohl, M. Krämer, T. C. Krisna, A. Luebke, B. Mayer, S. Mertes, S. Molleker, A. Petzold, K. Pfeilsticker, M. Port, R. Schlage, M. Schnaiter, J. Schneider, N. Spelten, P. Spichtinger, P. Stock, A. Walser, R. Weigel, B. Weinzierl, M. Wendisch, F. Werner, H. Wernli, M. Wirth, A. Zahn, H. Ziereis and M. Zöger (2017), ML-CIRRUS - The airborne experiment on natural cirrus and contrail cirrus with the high-altitude long-range research aircraft HALO, Bull. Amer. Meteor. Soc.98(2): 271-288, DOI: doi:10.1175/BAMS-D-15-00213.1