Coastal southeast Florida experiences a wide range of aerosol conditions, including African dust, biomass burning (BB) aerosols, as well as sea salt and other locally-emitted aerosols. These aerosols are important sources of cloud condensation nuclei (CCN), which play an essential role in governing cloud radiative properties. As marine environments dominate the surface of Earth, CCN characteristics in coastal southeast Florida have broad implications for other regions with the added feature that this site is perturbed by both natural and anthropogenic emissions. This study investigates the influence of different air mass types on CCN concentrations at 0.2% (CCN_0.2%) and 1.0% (CCN_1.0%) supersaturation (SS) based on ground site measurements during selected months in 2013, 2017, and 2018. Average CCN_0.2% and CCN_1.0% concentrations were 373 ± 200 cm⁻³ and 584 ± 323 cm⁻³, respectively, for four selected days with minimal presence of African dust and BB (i.e., background days). CCN concentrations were not elevated on the four days with highest influence of African dust (289 ± 104 cm⁻³ [0.2% SS] and 591 ± 302 cm⁻³ [1.0% SS]), consistent with high dust mass concentrations comprised of coarse particles that are few in number. In contrast, CCN concentrations were substantially enhanced on the five days with the greatest impact from BB (1408 ± 976 cm⁻³ [0.2% SS] and 3337 ± 1252 cm⁻³ [1.0% SS]). Ratios of CCN_0.2%:CCN_1.0% were used to compare the hygroscopicity of the aerosols associated with African dust, BB, and background days. Average ratios were similar for days impacted by African dust and BB (0.54 ± 0.17 and 0.55 ± 0.17, respectively). A 29% higher average ratio was observed on background days (0.71 ± 0.14), owing in part to a strong presence of sea salt and reduced presence of more hydrophobic species such as those of a carbonaceous or mineral-dust nature. Finally, periods of heavy rainfall were shown to effectively decrease both CCN_0.2% and CCN_1.0% concentrations. However, the rate varied at which such concentrations increased after the rain. This work contributes knowledge on the nucleating ability of African dust and BB in a marine environment after varying periods of atmospheric transport (days to weeks). The results can be used to understand the hygroscopicity of these air mass types, predict how they may influence cloud properties, and provide a valuable model constraint when predicting CCN concentrations in comparable situations.

佛罗里达州东南部沿海地区的气溶胶条件广泛，包括非洲粉尘，生物质燃烧（BB）气溶胶，海盐和其他本地排放的气溶胶。这些气溶胶是云凝结核（CCN）的重要来源，它们在控制云辐射特性中起着至关重要的作用。由于海洋环境主导着地球表面，佛罗里达州东南沿海的CCN特征对其他地区具有广泛的影响，其附加特征是该地点受到自然和人为排放的干扰。这项研究调查了不同空气质量对CCN浓度在0.2％（CCN _0.2％）和1.0％（CCN _{1.0％）时的影响}）（基于2013年，2017年和2018年选定月份的地面测量结果的过饱和度）。四个选定国家的平均CCN _0.2％和CCN _1.0％浓度分别为373±200 cm ^-3和584±323 cm ^-3非洲尘埃和BB最少存在的天数（即背景天）。在非洲尘埃影响最大的四天内，CCN浓度未升高（289±104 cm ^-3 [0.2％SS]和591±302 cm ^-3 [1.0％SS]），这与由粗尘组成的高尘埃浓度一致数量很少的粒子。相反，在五天内，BB的影响最大，CCN浓度显着提高（1408±976 cm ^-3[0.2％SS]和3337±1252 cm ^-3 [1.0％SS]）。使用CCN _0.2％：CCN _1.0％的比率来比较与非洲粉尘，BB和本底天数相关的气溶胶的吸湿性。受非洲扬尘和BB影响的天数的平均比率相似（分别为0.54±0.17和0.55±0.17）。在背景日观察到平均比率提高了29％（0.71±0.14），部分原因是大量存在海盐，并且减少了更多疏水性物质（如碳质或矿物粉尘性质）的存在。最后，大雨期间显示出有效减少CCN _0.2％和CCN _1.0％浓度。然而，雨后这种浓度增加的速率是变化的。这项工作为人们了解了经过不同时期的大气运输（数天至数周）之后，非洲尘埃和BB在海洋环境中的成核能力。结果可用于了解这些空气质量类型的吸湿性，预测它们如何影响云特性，并在可比情况下预测CCN浓度时提供有价值的模型约束。