Sources, Visibility and Climate Effects of Marine Aerosols

Liquid cloud and fog droplets, like steam from boiling water, form on pre-existing aerosol particles in the atmosphere, and the particle size and chemical composition affect their ability to turn into droplets. The number of particles can affect the reflectivity of a cloud or fog, which affects visibility in a fog or the fraction of sunlight transmitted through a cloud, thus affecting the Earth's energy budget. However, the link between particles, clouds and climate remains poorly constrained. The oceans, including coastal and polar regions, cover 70% of the Earth yet our understanding of the particles and particle precursors (i.e. gases) that they emit into the atmosphere are still highly uncertain as are the ultimate effect of marine particles on climate and visibility through cloud and fog formation. To address this, the proposed work will use a variety of techniques to 1) determine how surface ocean chemical and physical conditions affect the properties of marine aerosol particles in controlled laboratory settings and apply these findings to the ambient marine atmosphere through modelling studies; 2) test fog formation and visibility predictions at northern Canadian coastal locations through an extended crowd-sourced observation network and detailed observational studies; and 3) constrain aerosol-fog/cloud interactions in marine locations by determining the extent to which particle chemical and physical properties affect fog/cloud properties such as droplet concentration, visibility and reflectivity through field and modelling studies. Taken together, this research will improve our understanding of the sources and properties of marine, coastal, and polar aerosols as well as their impact on climate through their ability to activate as cloud droplets. It is expected that this work will directly benefit coastal residents, especially those living in the North, through improved fog predictions. This work will also benefit chemical transport modellers through improved characterization of primary and secondary marine aerosols, and climate modellers by providing sample data sets against which their simulations of aerosol-cloud interactions can be compared.