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

Abstract. 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 cloud-relevant environments still limited. During 2017 joint INUIT/CLACE (Ice Nuclei research UnIT/CLoud–Aerosol Characterization Experiment) field campaign, observations INPs as well physical chemical properties were performed, complemented region modeling. This aimed at investigating nature sources INPs. campaign took place High-Altitude Research Station Jungfraujoch (JFJ), location where frequently occur. Due to its altitude 3580 m a.s.l., station usually located lower free troposphere, but it can also receive air masses from terrestrial marine via long-range transport. INP concentrations quasi-continuously detected with Horizontal Ice Nucleation Chamber (HINC) under conditions representing −31 ∘C. measurements performed parallel two single-particle mass spectrometers, Aircraft-based Laser ABlation Aerosol MAss Spectrometer (ALABAMA) laser ablation particle time-of-flight spectrometer (LAAPTOF). identity inferred correlating time series ion signals measured spectrometers measurements. Moreover, our results are direct analysis residuals (IPRs) using an ice-selective inlet (Ice-CVI) coupled ALABAMA. Mineral dust aged sea spray showed highest correlations series. Their role further supported emission sensitivity transport modeling, which confirmed that advected Sahara during times elevated ice-active surface site densities. Indeed, IPR that, number, mineral dominated composition (∼58 %), biological metallic found smaller extent (∼10 % each). Sea IPRs (17 fraction strongly varied according increased presence small IPRs, likely due impact secondary crystal formation. study shows capability combining concentration characterization spectrometry, environment directly relevant for cloud