Abstract
Abstract. Modelling studies suggest that the climate and the hydrological cycle are sensitive to the concentrations of ice-nucleating particles (INPs). However, the concentrations, composition, and sources of INPs in the atmosphere remain uncertain. Here, we report daily concentrations of INPs in the immersion freezing mode and tracers of mineral dust (Al, Fe, Ti, and Mn), sea spray aerosol (Na+ and Cl−), and anthropogenic aerosol (Zn, Pb, NO3-, NH4+, and non-sea-salt SO42-) at Alert, Canada, during a 3-week campaign in March 2016. In total, 16 daily measurements of INPs are reported. The average INP concentrations measured in the immersion freezing mode were 0.005±0.002, 0.020±0.004, and 0.186±0.040 L−1 at −15, −20, and −25 ∘C, respectively. These concentrations are within the range of concentrations measured previously in the Arctic at ground level or sea level. Mineral dust tracers all correlated with INPs at −25 ∘C (correlation coefficient, R, ranged from 0.70 to 0.76), suggesting that mineral dust was a major contributor to the INP population at −25 ∘C. Particle dispersion modelling suggests that the source of the mineral dust may have been long-range transport from the Gobi Desert. Sea spray tracers were anti-correlated with INPs at −25 ∘C (R=-0.56). In addition, INP concentrations at −25 ∘C divided by mass concentrations of aluminum were anti-correlated with sea spray tracers (R=-0.51 and −0.55 for Na+ and Cl−, respectively), suggesting that the components of sea spray aerosol suppressed the ice-nucleating ability of mineral dust in the immersion freezing mode. Correlations between INPs and anthropogenic aerosol tracers were not statistically significant. These results will improve our understanding of INPs in the Arctic during spring.
Highlights
The formation of ice in clouds can be initiated by homogeneous or heterogeneous nucleation
ice-nucleating particles (INPs) concentrations at temperatures below −25 ◦C are not discussed since freezing of the blanks became significant at these temperatures
Since freezing was rarely observed at ≥ −25 ◦C in the blank experiments, the INP concentrations determined in the blank experiments were not subtracted from the INP concentrations reported in this study
Summary
The formation of ice in clouds can be initiated by homogeneous or heterogeneous nucleation. Heterogeneous nucleation of ice in clouds occurs on only a small subset of atmospheric particles, referred to as ice-nucleating particles (INPs) (Vali et al, 2015). INPs can change the frequency and properties of clouds in the atmosphere and influence climate and precipitation (Andreae and Rosenfeld, 2008; Curry, 1995; DeMott et al, 2010; Du et al, 2011; Lohmann and Feichter, 2005; Prenni et al, 2007; Xie et al, 2013). To predict precipitation and Earth’s climate, an understanding of the concentrations, composition, and sources of INPs in the atmosphere is required. INPs have been measured in the Arctic since as early as the 1970s
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
