Light-Absorbing Aerosol-Cloud Interactions

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

     Abstract Number: 746
     Working Group: Carbonaceous Aerosol

Abstract
Atmospheric light-absorbing aerosols, including those containing black carbon (BC) particles, play a critical role in determining Earth's radiation budget. These particles interact with solar radiation by scattering and absorbing light, as well as with clouds. However, the pathway by which BC-containing particles evolve in the atmosphere and internally mix with other substances, such as organics,significantly impacts their light scattering and absorption capabilities, as well as their interactions with clouds. Despite some prior research in this area, the effects of BC-cloud interactions have not received sufficient attention. Light-absorbing aerosol-cloud interactions (LAACI) is a project designed to investigate these processes using the Michigan Tech cloud chamber (the Pi Chamber). We utilized a BC surrogate (cab-o-jet) and a coating material surrogate (liquid smoke) to understand better some aerosol-cloud interactions. Notably, commercially available Liquid Smoke (LS) aerosols proved to be a suitable surrogate, chemically as well as physically, for non-refractory biomass burning aerosols to be employed as coating material on BC particles. We developed a procedure to coat particles comprised of the BC surrogate with LS. Cloud experiments employed a Pumped Counterflow Virtual Impactor (PCVI) to investigate changes in the morphology, optical, and chemical properties of the pure and coated BC residuals (particles that were activated at the time of sampling) and the interstitials (particles that were not activated at the time of sampling). Throughout these experiments, we monitored alterations in the optical and cloud condensation nuclei properties of both interstitial and residual particles, comparing them with the properties of the same particles before their introduction into the Pi-Chamber. In our experiments we saw that LS aerosols have a higher critical supersaturation for activation after its interaction with clouds in the Pi Chamber. It was also seen that for coated BC the residuals have different optical properties from the interstitial, the former being more absorbing than the latter.