Abstract. The impact of aerosols on clouds is a well-studied, although still poorly constrained, part of the atmospheric system. New particle formation (NPF) is thought to contribute 40–80 % of the global cloud droplet number concentration, although it is extremely difficult to observe an air mass from NPF to cloud formation. NPF and growth occurs frequently in the Canadian Arctic summer atmosphere, although only a few studies have characterized the source and properties of these aerosols. This study presents cloud condensation nuclei (CCN) concentrations measured on board the CCGS Amundsen in the eastern Canadian Arctic Archipelago from 23 July to 23 August 2016 as part of the Network on Climate and Aerosols: Addressing Uncertainties in Remote Canadian Environments (NETCARE). The study was dominated by frequent ultrafine particle and/or growth events, and particles smaller than 100 nm dominated the size distribution for 92 % of the study period. Using κ-Kohler theory and aerosol size distributions, the mean hygroscopicity parameter (κ) calculated for the entire study was 0.12 (0.06–0.12, 25th–75th percentile), suggesting that the condensable vapours that led to particle growth were primarily non-hygroscopic, which we infer to be organic. Based on past measurement and modelling studies from NETCARE and the Canadian Arctic, it seems likely that the source of these non-hygroscopic, organic, vapours is the ocean. Examining specific growth events suggests that the mode diameter (D_max) had to exceed 40 nm before CCN concentrations at 0.99 % SS started to increase, although a statistical analysis shows that CCN concentrations increased 13–274 cm⁻³ during all ultrafine particle and/or growth times (total particle concentrations > 500 cm⁻³, D_max < 100 nm) compared to Background times (total concentrations < 500 cm⁻³) at SS of 0.26–0.99 %. This value increased to 25–425 cm⁻³ if the growth times were limited to times when D_max was also larger than 40 nm. These results support past results from NETCARE by showing that the frequently observed ultrafine particle and growth events are dominated by a highly non-hygroscopic fraction, which we interpret to be organic vapours originating from the ocean, and that these growing particles can increase the background CCN concentrations at SS as low as 0.26 %, thus pointing to their potential contribution to cloud properties and thus climate through the radiation balance.

中文翻译：

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表征加拿大北极夏季生长颗粒的吸湿性

摘要。气溶胶对云的影响是大气系统的一个部分，虽然仍然受到很大限制，但已得到充分研究。新粒子形成 (NPF) 被认为占全球云滴数浓度的 40-80%，尽管观察从 NPF 到云形成的气团极其困难。NPF 和生长在加拿大北极夏季大气中经常发生，尽管只有少数研究描述了这些气溶胶的来源和特性。本研究介绍了在CCGS Amundsen上测量的云凝结核 (CCN) 浓度2016 年 7 月 23 日至 8 月 23 日在加拿大东部北极群岛作为气候和气溶胶网络的一部分：解决加拿大偏远环境中的不确定性 (NETCARE)。该研究主要是频繁的超细颗粒和/或生长事件，在 92% 的研究期间，小于 100 nm 的颗粒在尺寸分布中占主导地位。使用κ -Kohler 理论和气溶胶粒径分布，平均吸湿性参数 ( κ) 为整个研究计算为 0.12（0.06-0.12，第 25-75 个百分位数），表明导致颗粒生长的可冷凝蒸汽主要是非吸湿性的，我们推断它是有机的。根据 NETCARE 和加拿大北极地区过去的测量和建模研究，这些非吸湿性有机蒸气的来源似乎是海洋。检查特定生长事件表明模式直径（d_最大）具有在0.99％至超过CCN浓度之前为40nm SS开始加大，虽然统计分析表明CCN浓度增加13-274厘米^-3所有超微粒子和中/或生长时间（总颗粒浓度 > 500 cm ^-3 , D _max< 100 nm）与背景时间（总浓度 < 500 cm ^-3）相比，SS 为 0.26–0.99 %。如果生长时间仅限于D _max也大于 40 nm 的时间，则该值增加到 25–425 cm ^-3。这些结果支持 NETCARE 过去的结果，表明经常观察到的超细颗粒和生长事件由高度非吸湿性部分主导，我们将其解释为源自海洋的有机蒸气，并且这些生长的颗粒可以增加背景 CCN SS 的浓度低至 0.26%，从而表明它们通过辐射平衡对云特性和气候的潜在贡献。