Light-Absorbing Aerosol-Cloud Interactions

SHREYA JOSHI, Lynn Mazzoleni, Will Cantrell, Raymond Shaw, Simeon Schum, Thusitha Divisekara, Ian Helman, Abu Sayeed Md Shawon, Kyle Gorkowski, Timothy Onasch, Arthur J. Sedlacek, Ogochukwu Enekwizu, Yangang Liu, Laura Fierce, Payton Beeler, Kadja Flore Gali, Swarup China, Nurun Nahar Lata, Gregory W. Vandergrift, Gourihar Kulkarni, Claudio Mazzoleni, Michigan Technological University

     Abstract Number: 315
     Working Group: Carbonaceous Aerosols

Abstract
Light-absorbing aerosols, including black carbon (BC) containing particles, affect Earth's radiation budget through interactions with sunlight and influencing cloud formation and their properties. Aerosols facilitate cloud formation by acting as cloud condensation nuclei (CCN) or ice-nucleating particles. However, not all clouds precipitate; they can evaporate, reintroducing the aerosols into the atmosphere, where they may undergo further interactions with clouds. Such interactions can alter the properties of these particles in the atmosphere. Cloud chamber studies provide an opportunity to investigate the effects of BC-cloud interactions in controlled laboratory settings. The Light-Absorbing Aerosol-Cloud Interactions (LAACI) project, utilizing Michigan Tech's turbulent cloud Pi-chamber, was designed to study these interactions. Utilizing surrogates for BC (cab-o-jet) and the coating material (liquid smoke), we developed a procedure to produce coated BC-like particles, which underwent cloud interactions in the Pi-chamber. We studied three particle types: (1) uncoated BC, (2) BC coated with liquid smoke, and (3) liquid smoke particles alone. Using a pumped counterflow virtual impactor, we isolated cloud droplets and dried them, giving us cloud droplet residuals, while unactivated aerosols (i.e., interstitials) were collected using a separate horizontal aerosol line. We studied the evolution of the aerosol morphological, optical, and CCN properties for the different particle types within a laboratory-generated cloud by analyzing residuals and interstitials. Notably, a significant fraction of the coated BC residuals exhibited lower solidity than the injected particles, indicating a complex interaction between morphology and aerosol activation. We also saw a decrease in the retrieved real part of the refractive index in the residual particles and an increase in the mean size of the particle distribution. This research provides insights into the atmospheric aging of BC-containing particles and their impacts on climate and should help develop more accurate parametrizations for future atmospheric models.

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