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Refractive Index of Black Carbon (BC) and Brown Carbon (BrC) Particles with True Monodisperse Selection
DAWEI HU, Rami Alfarra, Kate Szpek, Justin Langridge, Chenjie Yu, Michael Cotterell, Claire Belcher, Ian Rule, Yunqi Shao, Aristeidis Voliotis, Zixia Liu, Dantong Liu, Jim Haywood, Hugh Coe, James Allan, University of Manchester
Abstract Number: 222
Working Group: Carbonaceous Aerosol
Abstract
The refractive index (RI) of black carbon (BC) and brown carbon (BrC) are important parameters to consider when predicting their radiative forcing in the atmosphere. Previous studies have used a differential mobility analyzer (DMA) to select mono-disperse BC/BrC particles to derive its RI according to a Mie model, which introduces large uncertainties associated with multiple charging. During the Soot Aerodynamic Size Selection for Optical properties (SASSO) project, we coupled a charging-free Cambustion Aerodynamic Aerosol Classifier (AAC) with the Met Office Extinction, Scattering and Absorption of Light for Airborne Aerosol Research (EXSCALABAR) system, delivering a high-resolution, multi-wavelength extinction and absorption measurements with truly mono-disperse cuts. Different types of light absorbing carbon were studied, including BC from catalytically stripped diesel exhaust and controlled flaming wood combustion. BrC was also investigated in the form of organic matter from wood burning (pyrolysis and smoldering) and ‘brown’ SOA produced in a chamber. Finally, coated particles were also investigated to test the accuracy of different mixing models used in optical treatments. The data generated from this study will be used to inform climate models, such as HadGEM at the UK Hadley Centre.