Probing Aerosol–Weather–Cloud Interactions with Multi-Instrument Measurements at the Onsala Space Observatory

Abstract

One of the key uncertainties in our understanding of the climate system is the production of aerosols and their interactions with clouds. The Onsala Space Observatory (OSO) provides an ideal site, at the land-sea interface, to address this knowledge gap, offering a comprehensive set of instruments for integrated in situ and remote-sensing observations. This thesis investigates the production mechanisms of aerosols - primarily sea salts - and their influence on clouds from late 2024 to early 2025, while confirming the local climate properties of the OSO site. To supplement existing observatory data, ground measurements at OSO and a drone flight at a nearby site were conducted using a Portable Optical Particle Spectrometer (POPS). Our findings confirm the previously established climatic baselines for the OSO site and highlight several key atmospheric relationships. Specifically, strong winds originating from the ocean correlate with high local aerosol concentrations, particularly sea salts; precipitation events drive aerosol scavenging (washout); and higher aerosol loading is directly associated with increased local cloud cover.