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.


  • project logo

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

  • 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 international CLACE (Cloud and Aerosol Characterization Experiment) and INUIT (Ice Nuclei research UnIT) cloud field measurement campaigns in order to pursue the above-mentioned scientific goals for heterogeneous ice formation in real clouds and thus for atmospheric ice nucleating particles. In order to consider the IPRs to be analysed as atmospheric ice nucleating particles, the diameter of the collected ice particles is limited by the Ice-CVI (< 20 µm), since up to this size ice particles grow only by water vapour diffusion and hardly scavenge interstitial aerosol. Several inlet components separate larger ice crystals, interstitial aerosol particles and supercooled droplets, whereby the geometries and fluxes are dimensioned in such a way that no ice particle shattering or droplet breakup occurs.

This project is funded by the German Research Foundation (DFG Research Group 1525, grant STR 453/7-2).


  • HALO logo

  • The research aircraft HALO with the HALO-CVI (third inlet from left) during ML-CIRRUS, Source: Stephan Mertes/TROPOS


ML-CIRRUS: Central Europe, Airborne (2014)

The scientific objectives of ML-CIRRUS (project page) are, among other things, the investigation of the formation and development of natural and airborne cirrus cirrus in mid-latitudes. For this purpose, cirrus cirrus in flight corridors and near airports but also in clean air masses were measured. The measurements took place in spring 2014 with the German research aircraft HALO over Western, Southern and Central Europe. The HALO-CVI inlet was used to chemically and microphysically analyse the residues of the cirrus ice particles.

This project was funded by the German Research Foundation (DFG Priority Programme 1294, grant ME 3534/1-2).



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