AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Characterization of Particle Number Size Distributions at Ground Level and 260 m on a Meteorological Tower in Beijing
Wei Du, Jian Zhao, Yingjie Zhang, YELE SUN, Inst. of Atmospheric Physics, Chinese Academy of Sciences
Abstract Number: 448 Working Group: Urban Aerosols
Abstract Despite extensive studies in characterization of the particle number size distributions at ground level in Beijing, real-time characterization above the urban canopy has never been performed to date. Here we conducted the first simultaneous real-time measurements of size-resolved particle number concentrations at two heights, i.e., ground and 260 m, at the same location in urban Beijing from August 22, 2015 to October 1, 2015 using two Scanning Mobility Particle Sizers (SMPS). Our results showed that the temporal variations of volume concentrations were similar between ground level and 260 m, while the number size distributions were significantly different. The number concentrations of accumulation mode particles (100 – 400 nm) at 260 m were higher than those at ground level (r$^2 = 0.85, slope = 1.17), those outside this size range were lower at higher heights. Detailed analysis suggests that the number differences at the two heights strongly depended on particle size. For example, higher number concentrations at smaller sizes were observed at ground level due to cooking emissions. New particle growth events (NPE) were occasionally observed throughout the study. The average growth rate (GR) was 3.6 nm h$^(-1) at 260 m and 3.2 nm h$^(-1) at ground level, respectively. Positive matrix factorization was also performed on size-resolved number concentrations and the sources of particle numbers at two different heights were compared and discussed.