Abstract. The western North Atlantic Ocean is strongly influenced by continental outflow, making it an ideal region to study the atmospheric transition from a polluted coastline to the marine environment. Utilizing eight transit flights between NASA Langley Research Center (LaRC) in Hampton, Virginia and the remote island of Bermuda from NASA’s Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE), we examine the evolution of trace gas and aerosol properties off the U.S. East Coast. The first pair of flights flew along the wind trajectory of continental outflow, while the other flights captured a mix of marine and continental air mass sources. For measurements within the boundary layer (BL), there was an offshore decline in particle N_{<100 nm}, N_{>100 nm}, CH₄, CO, and CO₂ concentrations, all leveling off around ~900 km offshore from LaRC. These trends are strongest for the first pair of flights. In the BL, offshore declines in organic mass fraction and increases in sulfate mass fraction coincide with increasing hygroscopicity based on f(RH) measurements. Free troposphere measurements show a decline in N_{<100 nm} but other measured parameters are more variable when compared to the prominent offshore gradients seen in the BL. Pollution layers exist in the free troposphere, such as smoke plumes, that can potentially entrain into the BL. This work provides detailed case studies with a broad set of high-resolution measurements to further our understanding of the transition between continental and marine environments.

中文翻译：

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连接美国东北部和百慕大之间的气体和气溶胶特性：八个过境航班的分析

摘要。北大西洋西部受到大陆流出的强烈影响，使其成为研究从污染的海岸线到海洋环境的大气转变的理想地区。利用美国宇航局西大西洋气溶胶云气象学相互作用实验 (ACTIVATE) 往返于弗吉尼亚州汉普顿的美国宇航局兰利研究中心 (LaRC) 和百慕大偏远岛屿之间的八次过境航班，我们研究了美国附近微量气体和气溶胶特性的演变东海岸。第一对航班沿着大陆流出的风轨迹飞行，而其他航班则捕获了海洋和大陆气团来源的混合。对于边界层 (BL) 内的测量，近海粒子 N _{<100 nm}、N _{>100 nm}、CH ₄、CO 和 CO ₂浓度均有所下降，均在距离 LaRC 近海约 900 公里处趋于平稳。这些趋势在第一对航班中最为强劲。在 BL 中，海上有机物质量分数的下降和硫酸盐质量分数的增加与基于 f(RH) 测​​量的吸湿性增加相一致。自由对流层测量显示 N _{<100 nm}下降，但与 BL 中看到的显着离岸梯度相比，其他测量参数变化更大。自由对流层中存在污染层，例如烟羽，可能会夹带进入 BL。这项工作提供了详细的案例研究和广泛的高分辨率测量，以进一步我们对大陆和海洋环境之间的转变的理解。