Heterogeneous ice nucleating particle (INP) concentrations are reported for a site on the eastern margin of Beijing, China, during the period 4 May to 4 June 2018. INP concentrations were measured continuously at −20, −25, and −30 °C in a repeating cycle by a newly developed, automated continuous flow diffusion chamber, and reached concentrations as high as 2800 sL−1 during dust‐impacted periods. Study average concentrations were 70 ± 70, 230 ± 290, and 430 ± 500 sL−1 at −20, −25, and −30 °C. There was no clear relationship between pollution periods, identified based on fine‐mode particle concentration increases, and INP concentrations or characteristics. Other anthropogenic emissions, such as non‐combustion industrial or agricultural activities play an unresolved role.
Wet scavenging of black carbon (BC) has been subject to large uncertainty, which importantly determines its atmospheric lifetime and indirect forcing impact on cloud microphysics. This study reveals the complex BC‐hydrometeor interactions in mixed‐phase clouds via single particle measurements in the real‐world environment, by capturing precipitation processes throughout cloud formation, cold rain/graupel, and subsequent snow events at a mountain site influenced by anthropogenic sources in wintertime. We found highly efficient BC wet scavenging during cloud formation, with large and thickly coated BC preferentially incorporated into droplets. During snow processes, BC core sizes in the interstitial phase steadily increased. A mechanism was proposed whereby the BC mass within each droplet was accumulated through droplet collision, leading to larger BC cores, which were then released back to the interstitial air through the Wegener‐Bergeron‐Findeisen processes when ice dominated. These results provide fundamental basis for constraining BC wet scavenging.
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