10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Marine Aerosol Cloud Activation
JURGITA OVADNEVAITE, Kirsten Fossum, Darius Ceburnis, Colin O’Dowd, National University of Ireland Galway, Ireland
Abstract Number: 516 Working Group: Clouds and Climate
Abstract Marine aerosol occurring in cloud condensation nucleus (CCN) sizes suggest that it may contribute notably to the CCN population, but further cloud droplet number concentration would strongly depend on the chemical aerosol composition and ambient (cloud) conditions, such as available water content, supersaturation and competition between the CCN of different composition (O'Dowd et al., 1999). Since the global importance of marine aerosol particles to the cloud formation postulated several decades ago, it has progressed from the evaluation of the nss-sulphate and sea salt effects to the acknowledgement of the significant role of organic aerosol (O'Dowd et al., 2004). It has been demonstrated that primary marine organics, despite its hydrophobic nature, can possess the high CCN activation efficiency, resulting in the efficient cloud formation (Ovadnevaite et al., 2011). Organic aerosol, ubiquitous in both clean and polluted atmosphere, can be present as a pure organic aerosol or and internally-mixed aerosol with other constituents such as sulphate and nitrate aerosol. The hygroscopicity of organic aerosol in sub-saturated humidity fields is typically less than most common salts found in the atmospheric aerosol; however, the ability of organic aerosol to activate cloud droplets is predicted to be greatly increased in supersaturated air due a lowering of the droplets surface tension, ultimately leading to more nuclei being activated at lower supersaturations (Facchini et al., 2000). While this phenomenon has been acknowledged for some time, we’ve demonstrated it in the real atmosphere (Ovadnevaite et al., 2017). Here we show the organic effect on primary and secondary marine aerosol activation to CCN. Results from two intensive measurement campaigns in the Eastern North Atlantic (Mace Head) and the Southern Ocean (PEGASO cruise) are presented here with the main focus on CCN dependence on aerosol chemical composition and, especially, origin and sources of marine organic. We investigate the activation of sea spray composed of the sea salt and externally mixed with nss-sulphate as well as the sea spray highly enriched in organics, stressing the importance of the latter to the formation of the cloud droplets. In addition, the organic effect on CCN activation of newly formed marine particles is investigated.
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