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Relationship between Aerosol and Precipitation Composition at a Coastal Site in the Southeast United States
ANDREA F CORRAL, Hossein Dadashazar, Connor Stahl, Eva-Lou Edwards, Paquita Zuidema, Armin Sorooshian, University of Arizona
Abstract Number: 204
Working Group: Aerosols, Clouds and Climate
Abstract
This study combines field data and modeling to characterize temporal trends and interrelationships between aerosol and precipitation chemistry as an alternative and indirect method to gain insight on aerosol-cloud interactions. Long-term aerosol and precipitation chemistry measurements from co-located monitoring sites in southern Florida between 2013 and 2018 were used for this analysis. A positive matrix factorization (PMF) model identified six potential emission sources impacting the study area. The PMF model solution yielded the following source profiles with varying monthly concentration profiles: (i) combustion; (ii) fresh sea salt; (iii) aged sea salt; (iv) secondary sulfate; (v) shipping emissions; and (vi) dust. Based on these results, concentration-weighted trajectory maps were developed to identify possible sources contributing to the PMF factors. Sea salt is shown to be the main source of cloud condensation nuclei (CCN), even during summertime, when African dust is an important aerosol source. This was likely due to sea salt particles larger than 2.5 µm participating in cloud processes and the site’s proximity to the coast (~25 km). Fresh sea salt rather than aged sea salt (depleted in Cl− due to NO3−) was more influential for aerosol and cloud processes. The highest mean annual deposition fluxes were attributed to Cl−, NO3−, SO42−, and Na+ between April – October, which were the more strongly precipitating months. The results of this study provide findings with regard to the combination of the following: (i) composition of particles serving as either the cloud condensation nuclei (CCN) or ice nuclei (IN) that eventually fall to the surface via wet deposition; (ii) uptake of species into existing droplets in cloud; and (iii) sub-cloud scavenging of different constituents.