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New Particle Formation over the Western North Atlantic Ocean: Results from the NAAMES Field Campaign
JIAOSHI ZHANG, Xianda Gong, Qian Xiao, Armin Wisthaler, Markus Müller, Sven Arne Philipp Schiller, Richard Moore, Luke Ziemba, Ewan Crosbie, Ryan Bennett, Jian Wang, Washington University in St. Louis
Abstract Number: 542
Working Group: Remote and Regional Atmospheric Aerosol
Abstract
New particle formation (NPF) in the remote marine environment can contribute substantially to aerosol and CCN population, therefore influencing the marine clouds and climate. In this study, we investigate the new particle formation over the Western North Atlantic Ocean (WNAO) in different seasons (winter, late spring and summer) using airborne measurements during the North Atlantic Aerosol and Marine Ecosystem Study (NAAMES) field campaign. The WNAO region is impacted by a variety of synoptic regimes that lead to different atmospheric transport among ocean, North American continent, and the Arctic. The airmasses sampled are classified into four representative categories (i.e., background, biomass burning, biogenic and continental pollution) using trace gas and VOCs measurements including CO, acetonitrile, benzene, acetone, and methanol.
NPF events were observed at a wide range of altitudes, from near ocean surface to upper free troposphere above 6 km. Vast majority of the NPF events were observed under background conditions with minimum influences from continental emissions. The newly formed particles in the background airmass coincided with elevated dimethylsulfide (DMS) mixing ratio, especially during late spring and summertime when ocean biological activities are relatively high. NPFs inside the marine boundary layer were mostly observed under postfrontal conditions, when airmasses originated from the Arctic. NPFs in the upper free troposphere were observed in the outflow of convective clouds with reduced aerosol surface area and elevated RH and DMS mixing ratio. Oxidation products of DMS are likely the major precursors during these NPF events. Newly formed particles were also observed in continental outflows from North America inside free troposphere, suggesting impact of continental emissions on NPF. The potential precursors and mechanisms for these NPF events, which occurred in different airmasses and at a range of altitudes, will be compared and summarized.