Lake Spray Aerosol Incorporated into Great Lakes Clouds

Aerosol particles are generated by wind-driven processes in regions with large bodies of freshwater, but the impact of these particles on cloud properties and processes is poorly understood. Lake spray aerosol (LSA) production from freshwater wave breaking has the potential to contribute to cloud formation and modify cloud properties by acting as cloud condensation nuclei (CCN) and ice nucleating particles (INPs). To examine whether LSA reaches cloud height and is incorporated into clouds over the Laurentian Great Lakes, sampling of atmospheric particles and cloud water was conducted over Lake Michigan during a summertime wave-breaking event with wave heights of >1.4 m and wind speeds of >9 m s(-1). Single-particle microscopy and spectroscopy identified ambient LSA that had composition (CaCO3 and organic material) and morphology (spherical) consistent with LSA generated in the laboratory from surface freshwater collected at the time of ambient sampling. Cloud water was aerosolized in the laboratory, and the resulting composition and morphology of the insoluble residues were similar to ambient and laboratory-generated LSA particles. Elemental mole ratios of LSA and cloud water demonstrated that clouds over the Great Lakes contain similar inorganic salt composition to that of LSA and freshwater lakes. Therefore, LSA is likely a source of CCN and possibly INPs over the Great Lakes, which could potentially influence lake-effect cloud formation and properties. This has important implications for cloud microphysical and radiative properties in the Great Lakes region, as well as other areas with large bodies of freshwater.