The hygroscopicity of marine aerosols may largely impact particle optical properties, cloud activation ability, and consequently the global climate system. This study highlights findings from real-time hygroscopicity and chemical composition measurements in three open-ocean cruises over the Atlantic Ocean. Spatial variations in hygroscopicity (κ) for marine boundary layer particles (≤300 nm) were provided for the first time covering nearly 100° of the latitude over the Atlantic Ocean, ranging from 0.14 to 1.06. Externally mixed particles with remarkably low hygroscopicity (0.14–0.16) were observed near the equator influenced by biomass burning emissions transported from Africa. For marine aerosols, a positive linear correlation evidently existed between κ and wind speed within a range of 5–15 m/s even for nanometer particles. A closure study shows that the measured κ of 300 nm particles is well explained by the bulk chemical composition. A good negative correlation between measured κ and the organic mass fraction in PM₁ for marine aerosols was found (slope = −2.26, R² = 0.44), while a different linear relationship appeared for continental aerosols at several sites (slope = −0.47, R² = 0.77). Accordingly, we provide a parameterization method to estimate bulk aerosol hygroscopicity both in continental and marine environments using particulate organic fractions.

中文翻译：

---

基于三个跨大西洋测量的偏远海洋环境中气溶胶吸湿性及其与化学成分的联系

海洋气溶胶的吸湿性可能在很大程度上影响粒子光学特性、云激活能力，从而影响全球气候系统。这项研究重点介绍了在大西洋上空的三艘公海巡航中的实时吸湿性和化学成分测量结果。首次提供了海洋边界层粒子（≤300 nm）的吸湿性（κ）空间变化，覆盖了大西洋近 100° 的纬度，范围从 0.14 到 1.06。在赤道附近观察到吸湿性非常低的外部混合颗粒（0.14-0.16），受非洲运输的生物质燃烧排放的影响。对于海洋气溶胶，即使是纳米粒子，在 5-15 m/s 范围内，κ 与风速之间也存在明显的正线性相关性。封闭研究表明，300 nm 粒子的测量 κ 很好地解释了整体化学成分。测量的 κ 与 PM 中的有机质量分数之间存在良好的负相关性发现海洋气溶胶为_{1 （斜率 = -2.26，} R ² = 0.44），而大陆气溶胶在几个地点出现了不同的线性关系（斜率 = -0.47，R ² = 0.77）。因此，我们提供了一种参数化方法来使用颗粒有机组分估计大陆和海洋环境中的散装气溶胶吸湿性。