Measurements of the Hygroscopic Growth of Aerosol Scattering Coefficients in Eastern China

Yan Peng(1), Li Weiliang(1), Liu Yu(1), Pan Xiaole(1), Tang Jie(1)

(1)Chinese Academy of Meteorological Sciences, Beijing

     Abstract Number: 486
     Last modified: May 13, 2010

Abstract
The hygroscopic growth of aerosol with increasing relative humidity is a key parameter in the study of climate forcing and visibility impairment. In the past several years, the light scattering coefficient (sigmasp) of aerosol particles and its dependency on relative humidity (RH), defined as the hygroscopic growth function/factor of aerosol scattering coefficient f(RH)= sigmasp(RH)/ sigmasp(dry), have been investigated through Integrating Nephelometers equipped with humidity control devices at CAMS site (urban site in Beijing), SDZ site (WMO GAW regional background monitoring station, Beijing), Baodi site (rural site in Tianjin), and LA site (WMO GAW regional background station) in Yangtze Delta region in the east part of China, respectively.
The statistics results indicated that in general, at all sites the observed hygroscopic growth showed smoothly and continuously with increasing RH, without displaying any obvious step-like deliquescent or “jumpy” behavior during the experiments. The average growth factor of aerosol scattering coefficients at 80% RH during the experiment periods ranged from 1.16 at the GAW regional background station (SDZ site) under clean conditions in the winter to 1.84 at the Beijing urban site (CAMS) under pollution conditions in the summer. Comparing the results obtained at the SDZ and the CAMS site, it was found that at both sites the f(RH) measured in the summer were significantly higher than those in winter, which reflected the summer chemical production of secondary aerosol could enhance the water-absorbing capability of aerosols. The limited chemical composition analysis of aerosols during the experiments suggested that sulfate could be the major contribution to the higher aerosol hygroscopic growth factor observed.