A43C-0301
Summer and winter time heterogeneity in aerosol single scattering albedo over the northwestern Atlantic Ocean during the TCAP field campaign: Relationship to chemical composition and mixing state

Thursday, 17 December 2015
Poster Hall (Moscone South)
Duli Chand1, Larry K Berg1, Jerome D Fast1, Alla Zelenyuk1, Jacqueline Mary Wilson1, Arthur J Sedlacek III2, Jason M Tomlinson1, John M Hubbe1, Jennifer M Comstock1, Fan Mei3, Evgueni Kassianov1 and Beat Schmid1, (1)Pacific Northwest National Laboratory, Richland, WA, United States, (2)Brookhaven National Lab, Upton, NY, United States, (3)Joint Global Change Research Institute, College Park, MD, United States
Abstract:
Aerosol play crucial role in earth’s radiative budget by scattering and absorbing solar radiation. The impact of aerosol on radiation budget depend on several factors including single scattering albedo (SSA), composition, and the growth processes, like coating or mixing.

We describe findings relevant to optical properties of aerosol characterized over the Cape Cod and nearby northwest Atlantic Ocean during the Two Column Aerosol Project (TCAP) during the summer (July 2012) and winter (February 2013) campaigns. The average single scattering albedo (SSA) shows distinctly different vertical profiles during the summer and winter periods. During the summer study period, the average SSA is greater than 0.95 near surface, it increases to 0.97 until an altitude of 2.5 km, and then decreases to 0.94 at top of the column near 4 km. In contrast, during the winter study period the average SSA is less than 0.93 and decreases with height reaching an average value of 0.87 near the top of the column. The large difference in summer and winter time SSA is linked to the presence of biomass burning (BB) aerosol rather than black carbon or soot in both seasons. In our study, the BB on average is factor of two higher in free troposphere (FT) during summer and more than a factor of two higher in the boundary layer during winter. Single particle analysis indicates that the average profiles of refractory black carbon (rBC) mass are similar in both seasons. The average rBC size are similar at all altitudes sampled (0-4 km) in summer time but different during winter time. In addition, the particles sampled in the summertime FT appear to be more aged than those seen during winter. The observed large heterogeneity in SSA and its links to the particle coating and composition highlights the importance of aging and mixing processes of aerosol in this region and represents a challenge for both regional and global scale models.

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