AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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CARES 2010: Diurnal Variation in the Mixing State of Black Carbon Aerosols in Sacramento, CA
R. SUBRAMANIAN, Janarjan Bhandari, Noopur Sharma, Swarup China, Claudio Mazzoleni, Rahul Zaveri, Adam Ahern, Carnegie Mellon University
Abstract Number: 385 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Direct radiative forcing by BC-containing aerosols (BCA) is affected by the relative fraction of non-BC material and particle morphology – collectively referred to as “mixing state”. In June 2010, as part of the CARES field campaign, a DMT single particle soot photometer (SP2) was deployed in the Sacramento, CA urban area. The SP2 detects single particle BC masses over 0.5 fg, and also provides information on the BC mixing state at the single-particle-level for a narrower range of aerosol sizes. The SP2 deployed at CARES reported mixing state information for BCA larger than ~170 nm optical diameter. The mixing state can be represented using either the incandescent lag, or the coating thickness assuming core-shell morphology and using the Leading Edge Only (LEO) optimization technique. The incandescent lag method shows a diurnal variation in the BC mixing state, with a greater fraction of thickly-coated BCA in the afternoon (~17%) than in the morning (~11%). However, preliminary results with LEO are not as clear. Our investigations will examine the relationship between the binary classification of the incandescent lag method and the more quantitative LEO technique. These results will be compared to SEM images collected at the site over periods ranging from 2-6 hours.