Investigating the phase state and photochemical ageing of brown carbon and its impact on microphysical and optical properties of aerosols and clouds

• Applicant: Stephanie Jones, Ph.D.
• Subject Area: Atmospheric Science
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 465375365

The understanding of how light absorbing atmospheric aerosol, specifically brown carbon (BrC) aerosol, affects the climate remains a key uncertainty in atmospheric science. Preliminary experiments conducted on single droplets of BrC aerosol have shown that common atmospheric processes such as aerosol evaporation and simulated solar irradiation result in a change in aerosol phase state from liquid droplets to a semi-solid phase. This change in phase state will impact on the formation of cloud droplets and subsequent cloud optical properties (e.g. the absorption and scattering of solar radiation and cloud lifetime). Therefore, this proposal aims to determine the impact of BrC aerosol phase state and photochemical ageing on the microphysical and optical properties of aerosols and clouds. Experiments propose to utilise the facilities at the Institute of Meteorology and Climate Research - Atmospheric Aerosol Research (IMK-AAF), at Karlsruhe Institute of Technology (KIT) including single particle experiments conducted using an Electrodynamic Balance (EDB) and aerosol ensemble measurements conducted using the Aerosol Interactions and Dynamics in the Atmosphere (AIDA) cloud chamber. Key objectives of the project involving single particle measurements include: the investigation of the phase state and morphology of different types of BrC aerosol over a range of atmospherically relevant conditions, determination of the phase state of BrC aerosol when mixed with an inorganic component, and determination of the effect of photochemical ageing on the phase state, chemical composition and optical properties of BrC aerosol. Key objectives of the project involving aerosol ensemble measurements are to investigate the effect of BrC aerosol phase state and photochemical ageing on cloud droplet formation, ice nucleation and associated aerosol and cloud optical properties. Overall, this project will increase understanding of the role of light absorbing aerosol in the climate.

• DFG Programme: Research Grants