Experimental development of a lake spray source function and its model implementation for Great Lakes surface emissions

Lake spray aerosols (LSAs) are generated from freshwater breaking waves in a mechanism similar to their saltwater counterparts, sea spray aerosols (SSAs). Unlike the well-established research field pertaining to SSAs, studying LSAs is an emerging research topic due to their potential impacts on regional cloud processes and their association with the aerosolization of freshwater pathogens. A better understanding of these climatic and public health impacts requires the inclusion of LSA emission in atmospheric models, yet a major hurdle to this inclusion is the lack of a lake spray source function (LSSF), namely an LSA emission parameterization. Here, we develop an LSSF based on measurements of foam area and the corresponding LSA emission flux in a marine aerosol reference tank (MART). A sea spray source function (SSSF) is also developed for comparison. The developed LSSF and SSSF are then implemented in the Community Multiscale Air Quality (CMAQ) model to simulate particle emissions from the Great Lakes surface from 10 to 30 November 2016. Measurements in the MART revealed that the average SSA total number concentration was 8 times higher than that of LSA. Over the 0.01–10 µm aerosol diameter size range, the developed LSSF was around 1 order of magnitude lower than the SSSF and around 2 orders of magnitude lower for aerosols with diameters between 1 and 3 µm. Model results revealed that LSA emission flux from the Great Lakes surface can reach ∼105 m−2 s−1 during an episodic event of high wind speeds. These emissions only increased the average total aerosol number concentrations in the region by up to 1.65 %, yet their impact on coarse-mode aerosols was much more significant, with up to a 19-fold increase in some areas. The increase in aerosol loading was mostly near the source region, yet LSA particles were transported up to 1000 km inland. Above the lakes, LSA particles reached the cloud layer, where the total and coarse-mode particle concentrations increased by up to 3 % and 98 %, respectively. Overall, this study helps quantify LSA emission and its impact on regional aerosol loading and the cloud layer.