10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Characteristics of Cloud Condensation Nuclei in an Urban Region of Central Taiwan
TA-CHIH HSIAO, Wei-Jen Hsieh, Neng-Huei Lin, Chun-Chiang Kuo, National Central University
Abstract Number: 496 Working Group: Clouds and Climate
Abstract Cloud condensation nuclei (CCN) constitute a crucial fraction of atmospheric aerosols (Burkart et al., 2011). The physical and chemical characteristics of CCN is closely related to cloud development and precipitation process (Andreae and Rosenfeld, 2008). In urban region, traffic emissions, containing fresh small particles and hydrophobic substance, could be the major source for local air pollutions (Souto-Oliveira et al., 2016) and influencing the aerosols hygroscopicity and CCN’s characteristics. Moreover, as aerosols released to atmospheric environment, different “aging processes”, such as condensation, coagulation and oxidation, would change its physiochemical properties and enhance homogeneity as well as hygroscopicity of particles (Gunthe et al., 2011). In this study, CCN’s characteristics in Taichung city, which is the major metropolitan region in central Taiwan, was quantified by the activation ratio (AR = CCN number concentration/condensation nuclei concentration) during Sept. 2017 to Feb. 2018. The experimental hygroscopicity, κexp, proposed by Petters and Kreidenweis (2007) under the scheme of Kӧhler theory was further derived using AR and collocated particle size distribution (PSD) measurements. On the other hand, κchem was estimated based on the real-time aerosol chemical compositions, which were monitored by a PILS-IC system. The analysis between AR, particle size and hygroscopicity revealed two distinct groups of CCN characteristics in central Taiwan. One demonstrated a positive correlation with particle size and AR, and the other presented a relatively weak correlation. This suggests particle size and its chemical composition could both play important roles in aerosol’s hygroscopicity and CCN’s activity. Our data also show that κchem and AR is a function of wind direction (WD) and wind speed (WS), generally with higher values associated with winds from the south. The potential source contribution function (PSCF) analysis is further employed to investigate the contributions of potential local emission sources.