Aircraft measurements of aerosol and trace gas chemistry in the eastern North Atlantic

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Zawadowicz, Maria A., Suski, Kaitlyn, Liu, Jiumeng, Pekour, Mikhail, Fast, Jerome, Mei, Fan, Sedlacek, Arthur J., Springston, Stephen, Wang, Yang, Zaveri, Rahul A., Wood, Robert, Wang, Jian, Shilling, John E.
• Language: unknown
• Published: 2021
• Subjects: 54 ENVIRONMENTAL SCIENCES; North Atlantic
• Online Access: http://www.osti.gov/servlets/purl/1811667; https://www.osti.gov/biblio/1811667; https://doi.org/10.5194/acp-21-7983-2021

The Aerosol and Cloud Experiment in the Eastern North Atlantic (ACE-ENA) investigated properties of aerosols and subtropical marine boundary layer (MBL) clouds. Low subtropical marine clouds can have a large effect on Earth's radiative budget, but they are poorly represented in global climate models. In order to understand their radiative effects, it is imperative to understand the composition and sources of the MBL cloud condensation nuclei (CCN). The campaign consisted of two intensive operation periods (IOPs) (June–July 2017 and January–February 2018) during which an instrumented G-1 aircraft was deployed from Lajes Field on Terceira Island in the Azores, Portugal. The G-1 conducted research flights in the vicinity of the Atmospheric Radiation Measurement (ARM) Eastern North Atlantic (ENA) atmospheric observatory on Graciosa Island. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and Ionicon proton-transfer-reaction mass spectrometer (PTR-MS) were deployed aboard the aircraft, characterizing chemistry of non-refractory aerosol and trace gases, respectively. The eastern North Atlantic region was found to be very clean, with an average non-refractory submicrometer aerosol mass loading of 0.6 µg m -3 in the summer and 0.1 µg m -3 in the winter, measured by the AMS. Average concentrations of the trace reactive gases methanol and acetone were 1–2 ppb; benzene, toluene and isoprene were even lower, <1 ppb. Mass fractions of sulfate, organics, ammonium and nitrate in the boundary layer were 69%, 23%, 7% and 1% and remained largely similar between seasons. The aerosol chemical composition was dominated by sulfate and highly processed organics. Particulate methanesulfonic acid (MSA), a well-known secondary biogenic marine species, was detected, with an average boundary layer concentration of 0.021 µg m -3 , along with its gas-phase precursor, dimethyl sulfide (DMS). MSA accounted for no more than 3% of the submicron, non-refractory aerosol in the boundary layer. Examination of ...