Sources and nature of ice-nucleating particles in the free troposphere at Jungfraujoch in winter 2017

• Main Authors: Lacher, Larissa, Clemen, Hans-Christian, Shen, Xiaoli, Mertes, Stephan, Gysel-Beer, Martin, Moallemi, Alireza, Steinbacher, Martin, Henne, Stephan, Saathoff, Harald, Möhler, Ottmar, Höhler, Kristina, Schiebel, Thea, Weber, Daniel, Schrod, Jann, Schneider, Johannes, Kanji, Zamin A
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus 2021
• Subjects: Alabama; inuit
• Online Access: https://hdl.handle.net/20.500.11850/518601; https://doi.org/10.3929/ethz-b-000518601

Primary ice formation in mixed-phase clouds is initiated by a minute subset of the ambient aerosol population, called ice-nucleating particles (INPs). The knowledge about their atmospheric concentration, composition, and source in cloud-relevant environments is still limited. During the 2017 joint INUIT/CLACE (Ice Nuclei research UnIT/CLoud-Aerosol Characterization Experiment) field campaign, observations of INPs as well as of aerosol physical and chemical properties were performed, complemented by source region modeling. This aimed at investigating the nature and sources of INPs. The campaign took place at the High-Altitude Research Station Jungfraujoch (JFJ), a location where mixed-phase clouds frequently occur. Due to its altitude of 3580ma.s.l., the station is usually located in the lower free troposphere, but it can also receive air masses from terrestrial and marine sources via long-range transport. INP concentrations were quasi-continuously detected with the Horizontal Ice Nucleation Chamber (HINC) under conditions representing the formation of mixed-phase clouds at 31 degrees C. The INP measurements were performed in parallel to aerosol measurements from two single-particle mass spectrometers, the Aircraft-based Laser ABlation Aerosol MAss Spectrometer (ALABAMA) and the laser ablation aerosol particle time-of-flight mass spectrometer (LAAPTOF). The chemical identity of INPs is inferred by correlating the time series of ion signals measured by the mass spectrometers with the time series of INP measurements. Moreover, our results are complemented by the direct analysis of ice particle residuals (IPRs) by using an ice-selective inlet (IceCVI) coupled with the ALABAMA. Mineral dust particles and aged sea spray particles showed the highest correlations with the INP time series. Their role as INPs is further supported by source emission sensitivity analysis using atmospheric transport modeling, which confirmed that air masses were advected from the Sahara and marine environments during times of elevated INP ...