Observational study on the radiative properties of aerosol at two regional GAW stations in the east part of China

Abstract: Since April 2003,field observations on aerosol chemical, physical and radiative properties at two regional background monitoring stations in the east part of China were conducted by the project "Measurement of aerosol chemical, physical and radiative properties in Yangtze Delta region", and the project "An observational study on the continental baseline air over China". The measurements were made at Lin'An (Zhejiang province) and Shangdianzi (about 150 km northeast of Beijing) background air monitoring stations (also regional GAW stations), and lasted over 1 year. The items measured were: aerosol scattering and absorption coefficients, size resolved aerosol mass, ions and elements, EC/OC compositions, and optical depth, etc. In this paper we briefly introduced the observations and primarily analyzed the characteristics of aerosol scattering and absorption properties at the two sites.

The instruments for scattering and absorption coefficients measurement at both sites were M9003 (ECOTECH) single band (525nm) Nephelometer, and AE31 (Magee Scientific Company) 7-band Aethalometer. Data were recorded at 5 min interval. At Shangdianzi, absorption measurement started in April 2003, and scattering measurement in September 2003.At Lin'An, the scattering and absorption measurement started in the middle of July 2003. The primary analysis indicated that: the monthly mean absorption coefficient of aerosol at Lin'An station during the observational period was about 56~133Mm-1, the scattering coefficient was 152~364Mm-1 and the single scattering albedo (SSA) was 0.72~0.82. This SSA was much lower than the mean values of SSA in the north hemisphere obtained from AERONET (Dubovik etal,2002), and also much lower than the previous measurement made by Xu (Xu etal,2002) at the same site in November 1999, in their measurements the mean (standard deviation) absorption coefficient were 23(14)Mm-1, scattering coefficient were 353(202)Mm-1,single scattering albedo were 0.93 (0.04). The monthly mean absorption coefficient at Shangdianzi station was 11~40 Mm-1, scattering coefficient was 76~282 Mm-1, and single scattering albedo (SSA) was 0.81~0.94. The seasonal variation of absorption and scattering coefficient in the two regions showed that: both scattering and absorption coefficient were lower in summer and higher in winter at Lin'An, but the monthly variations were more complicated at Shangdianzi,which was mainly related to the wind in that region.

Keywords: Rural sites Aerosol Scattering/Absorption coefficient Single Scattering Albedo (SSA)