Abstract
Aerosol scattering and absorption properties were continuously measured and analyzed at the urban Laboratory for Information Engineering in Surveying, Mapping and Remote Sensing (LIESMARS) site in Wuhan, central China, from 1 December 2009 to 31 March 2014. The mean aerosol scattering coefficient , absorption coefficient , and single scattering albedo (SSA) were 377.54 Mm−1, 119.06 Mm−1, and 0.73, respectively. Both and showed obvious annual variability with large values in winter and small values in summer, principally caused by the annual characteristics of meteorological conditions, especially planetary boundary layer height (PBLH) and local emissions. The SSA showed a slight annual variation. High values of SSA were related to formation of secondary aerosols in winter hazes and aerosol hygroscopic growth in humid summer. The large SSA in June can be attributed to the biomass combustion in Hubei and surrounding provinces. Both and showed double peak phenomena in diurnal variation resulting from the shallow stable PBLH at night and automobile exhaust emission during morning rush hours. The SSA also exhibited a double peak phenomenon related to the proportional variation of black carbon (BC) and light scattering particulates in the day and night. The long-term exploration on quantified aerosol optical properties can help offer scientific basis of introducing timely environmental policies for local government.
Highlights
Atmosphere aerosols can alter the climate system through aerosol radiative forcing via two modes: those that directly scatter and absorb sunlight and those that indirectly transform the physical and optical characteristics of clouds by serving as cloud condensation nuclei [1–3]
The aerosol absorption coefficient at the wavelength of 520 nm was adopted in the experiment, because the wavelength was close to 550 nm, which was the wavelength of scattering coefficient used in this study
A similar performance of aerosol optical parameters was noted in other urban cities in China [14,22,26,42]. 99th percent of σ and σ were extremely large at 1518.65 Mm−1 and 133.66 Mm−1, respectively, which can mainly be attributed to severe haze events occurring in winter
Summary
Atmosphere aerosols can alter the climate system through aerosol radiative forcing via two modes: those that directly scatter and absorb sunlight and those that indirectly transform the physical and optical characteristics of clouds by serving as cloud condensation nuclei [1–3]. Aerosols in the atmosphere have highly inhomogeneous spatiotemporal distribution and variability [4,5], which create the largest uncertainties among all climate forcing factors [6]. The current effects of aerosols are rarely considered in climate models [7]. Analysis of aerosol characteristics in various regions worldwide is necessary for understanding their climate effects. Long-term aerosol observations based on in-situ measurements would improve the precision of parameterizations in models and reduce uncertainties caused by an absence of aerosol information [8,9]. Comprehensive measurements have been extensively conducted worldwide in such projects as Aerosol Characterization Experiment (ACE); Aerosols, Clouds, and Trace Gases Research
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