Abstract View
Mixing State and Properties of Aged Aerosols in the North Atlantic Free Troposphere
MEGAN MORGENSTERN, Rhenton Brimberry, Nurun Nahar Lata, Swarup China, Lynn Mazzoleni, Paulo Fiahlo, Diamantino Henriques, Andrea Baccarini, Silvia Henning, Birgit Wehner, Bo Zhang, Simeon Schum, Claudio Mazzoleni, Michigan Technological University
Abstract Number: 560
Working Group: Aerosols, Clouds and Climate
Abstract
Aerosols influence several physical and chemical processes in our atmosphere, with interactions depending on their properties. As aerosols travel, they age, and these properties transform. While important, characterization of ‘well-aged’ particles in remote regions is scarce, often due to logistical challenges. To fill this gap, we collected and analyzed well-aged particles from Pico Mountain Observatory in the Azores in the North Atlantic.
Analysis included computer controlled scanning electron microscopy with energy dispersive X-ray spectroscopy, and scanning transmission X-ray microscopy with near-edge X-ray absorption fine structure spectroscopy on samples from June and July of 2015 and 2017. The micro-spectroscopic analyses were used to determine the mixing state parameter (χ) of each sample. The mixing state parameter is a numerical representation of how similar (internally mixed) or different (externally mixed) the particles’ elemental composition in the sample is. The elemental composition was also used to determine the particles’ hygroscopicity. Data from a collocated nephelometer and aethalometer were used to determine the scattering and absorption Angström exponents and the single scattering albedo. The Angström exponents provide information about the aerosol size and chemical composition, while the single scattering albedo determines their radiative forcing. For 2017, we also measured cloud condensation nuclei concentrations (CCNc). The aerosol transport and potential sources were investigated using the FLEXible PARTicle dispersion model (FLEXPART).
Aerosol composition varied, with groupings such as carbonaceous, sea salt, and dust. The FLEXPART analysis also suggested different potential sources and source regions, such as dust from North Africa, and biomass burning aerosols from North America. We will present the analyses of - and links between - the aerosol mixing state, composition, optical properties, hygroscopicity, and CCNc. These analyses can help understand how aerosol aging affects their interactions with radiation and clouds.