AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Aerosol Optical Properties Measurements by CAPS Single Scattering Albedo Monitor: Comparisons between Summer and Winter in Beijing, China
TINGTING HAN, Weiqi Xu, Jian Zhao, Chen Chen, Qingqing Wang, Li Jie, Zifa Wang, Xingang Liu, Yele Sun, Institute of Atmospheric Physics, Chinese Academy of Science
Abstract Number: 296 Working Group: Urban Aerosols
Abstract We have investigated aerosol optical properties in summer and winter in Beijing using a state-of-the-art cavity attenuated phase shift single scattering albedo monitor (CAPS PM$_ssa) that simultaneously measures airborne particle light extinction and scattering coefficients and thus SSA. Aerosol particle compositions were simultaneously measured by Aerosol Mass Spectrometer, Aerosol Chemical Speciation Monitor , and Aethalometers. Our results showed that the frequency distributions of SSA measured by CAPS PM$_ssa overall agree with those derived from the measurements by a CAPS extinction monitor and Aethalometers. However, significant differences were observed during periods with low SSA values in summer and winter. The average (±σ) extinction coefficient (b$_ext) and absorption coefficient (b$_ap) were 335.9 (±342.5) M m$^(-1) and 44.4 (±41.2) M m$^(-1), respectively during wintertime, which were approximately twice those observed in summer. In contrast, the average SSA was relatively close, 0.86 and 0.85 in summer and winter respectively. Further analysis showed that the variations in SSA can be approximately parameterized as a function secondary particulate matter or secondary inorganic aerosols during both seasons. Finally, we quantified the contributions of aerosol components to extinction coefficients in the two seasons. Our results showed that the light extinction was dominantly contributed by ammonium sulfate (30%) and secondary organic aerosol (SOA) (22%) in summer. In contrast, SOA (39%) was the largest contributor to light extinction in winter followed by ammonium nitrate (18%).