Open AccessAerosol optical properties retrieved from Sun photometer measurements over Shanghai, China
Author(s) -
He Qianshan,
Li Chengcai,
Geng Fuhai,
Yang Hequn,
Li Peiren,
Li Tingting,
Liu Dongwei,
Pei Zhen
Publication year - 2012
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2011jd017220
Subject(s) - sun photometer , aerosol , angstrom exponent , single scattering albedo , angstrom , environmental science , atmospheric sciences , wavelength , effective radius , volume (thermodynamics) , radius , photometer , meteorology , physics , astrophysics , optics , chemistry , computer security , quantum mechanics , galaxy , computer science , crystallography
Using a CIMEL Sun photometer, we conducted continuous observations over the urban area of Shanghai (31°14′N, 121°32′E) from 18 April 2007 to 31 January 2009. The aerosol optical depth (AOD), Angstrom wavelength exponent, single scattering albedo ( ω 0 ), and aerosol particle size distribution were derived from the observational data. The monthly mean AOD reached a maximum value of 1.20 in June and a minimum value of 0.43 in January. The monthly averaged Angstrom wavelength exponent reached a minimum value of 1.15 in April and a maximum value of 1.41 in October. The frequencies of the AOD and Angstrom wavelength exponent presented lognormal distributions. The averaged ω 0 at 550 nm was 0.94 throughout the observation period, indicating that the aerosols over Shanghai are composed mainly of scattering particles. The concentrations of coarse mode and accumulation mode aerosols over Shanghai were highest in spring compared with other seasons, especially for those particles with radii between 1.0 and 2.0 μ m. The median radius of monthly averaged accumulation mode aerosols increased with increasing AOD, and fine particles accounted for the majority of the aerosol volume concentration. The ratios of the monthly averaged volume concentration of accumulation mode and coarse mode aerosols (V f /V c ) were over 0.6 for all months studied and reached up to 1.94 in August. The volumes of the two modes changed with AOD, but their correlations presented different sensitivities, that is, the volume concentration of accumulation mode aerosols was more sensitive to variations in AOD than that of coarse mode aerosols. The aerosol volume concentration decreased with increasing ω 0 , indicating that the higher the volume concentration of aerosols, the higher the absorption in particle extinction properties. The increase in absorption was caused primarily by secondary species coated on black carbon (BC) and primary organic carbon (POC) particles.