Aerosol optical properties and direct radiative forcing based on measurements from the China Aerosol Remote Sensing Network (CARSNET) in eastern China
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Published:2018-01-15
Issue:1
Volume:18
Page:405-425
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ISSN:1680-7324
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Container-title:Atmospheric Chemistry and Physics
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language:en
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Short-container-title:Atmos. Chem. Phys.
Author:
Che HuizhengORCID, Qi Bing, Zhao Hujia, Xia XiangaoORCID, Eck Thomas F., Goloub Philippe, Dubovik OlegORCID, Estelles Victor, Cuevas-Agulló EmilioORCID, Blarel Luc, Wu Yunfei, Zhu Jun, Du Rongguang, Wang Yaqiang, Wang Hong, Gui Ke, Yu Jie, Zheng Yu, Sun Tianze, Chen Quanliang, Shi Guangyu, Zhang Xiaoye
Abstract
Abstract. Aerosol pollution in eastern China is an unfortunate consequence of the
region's rapid economic and industrial growth. Here, sun photometer
measurements from seven sites in the Yangtze River Delta (YRD) from 2011 to
2015 were used to characterize the climatology of aerosol microphysical and
optical properties, calculate direct aerosol radiative forcing (DARF) and
classify the aerosols based on size and absorption. Bimodal size
distributions were found throughout the year, but larger volumes and
effective radii of fine-mode particles occurred in June and September due to
hygroscopic growth and/or cloud processing. Increases in the fine-mode particles in
June and September caused AOD440 nm > 1.00 at most sites, and
annual mean AOD440 nm values of 0.71–0.76 were found at the urban sites
and 0.68 at the rural site. Unlike northern China, the AOD440 nm was
lower in July and August (∼ 0.40–0.60) than in January and
February (0.71–0.89) due to particle dispersion associated with subtropical
anticyclones in summer. Low volumes and large bandwidths of both fine-mode and
coarse-mode aerosol size distributions occurred in July and August because
of biomass burning. Single-scattering albedos at 440 nm (SSA440 nm)
from 0.91 to 0.94 indicated particles with relatively strong to moderate
absorption. Strongly absorbing particles from biomass burning with a
significant SSA wavelength dependence were found in July and August at most
sites, while coarse particles in March to May were mineral dust. Absorbing
aerosols were distributed more or less homogeneously throughout the region
with absorption aerosol optical depths at 440 nm ∼ 0.04–0.06,
but inter-site differences in the absorption Angström exponent indicate
a degree of spatial heterogeneity in particle composition. The annual mean
DARF was −93 ± 44 to −79 ± 39 W m−2 at the Earth's
surface and ∼ −40 W m−2 at the top of the atmosphere
(for the solar zenith angle range of 50 to 80∘) under cloud-free
conditions. The fine mode composed a major contribution of the absorbing
particles in the classification scheme based on SSA, fine-mode fraction and
extinction Angström exponent. This study contributes to our
understanding of aerosols and regional climate/air quality, and the results
will be useful for validating satellite retrievals and for improving climate
models and remote sensing algorithms.
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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