AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Vertical Characteristics of Particle Number Size Distributions in the Megacity of Beijing, China
WEI DU, Yele Sun, Jian Zhao, Yuying Wang, Yingjie Zhang, Conghui Xie, Qingqing Wang, Weiqi Xu, Wei Zhou, Tingting Han, Inst. of Atmospheric Physics, Chinese Academy of Sciences
Abstract Number: 540 Working Group: Urban Aerosols
Abstract Understanding the particle number size distributions in atmospheric environments is important to investigate the mechanism of haze formation, while our knowledge of the vertical characteristics of particle number size distributions remains poor. The simultaneous measurements of size-resolved particle number concentrations were performed at ground level in the size range from 10 to 550 nm and at 260 m in the size range from 14 to 736 nm in urban Beijing from 21 November to 13 December, 2016 using two Scanning Mobility Particle Sizers (SMPS). Our results showed significant differences between the particle number size distribution at ground level and that at 260 m. The average number concentration in the size range between 20 nm and 550 nm at 260 m was 10312 cm-3, which was 39% lower than the ground level value of 16889 cm-3. The evolution of size-resolved ratio between 260 m and ground level changed dramatically throughout the observation. For example, the ratios in the whole size range were smaller than 0.6 during the scavenging of haze. The diurnal evolution of ratios showed higher values during daytime, and reached high peaks in the afternoon. Detailed analysis suggests that meteorological conditions (e.g. wind, relative humidity), pollution intensity, and sources had great impact on the vertical distribution of particle number concentrations. For example, relative humidity had a stronger impact on large Aitken mode particles at ground level while it had much smaller influence at 260 m. The ratios between 260 m and ground level were increased with the rise of total number concentrations. In addition, new particle growth events (NPE) were occasionally observed throughout the study, and the different mechanism between different heights were also compared and discussed.