Abstract
A severe haze episode that occurred in Wuhan, central China, from 6–14 June 2012 was investigated using ground-based and satellite-derived observations, from which the optical properties and vertical distribution of the aerosols were obtained. The mass concentrations of PM2.5 and black carbon (BC) were 9.9 (332.79 versus 33.66 μg∙m−3) and 3.2 times (9.67 versus 2.99 μg∙m−3) greater, respectively, on haze days than during normal weather. The large aerosol loading contributed to the high values of the scattering (2.32 km−1) and absorption coefficients (0.086 km−1). Particle size became larger, consistent with the reduced scattering Ångström exponent. The high asymmetry parameter (0.65) and single scattering albedo (SSA) (0.97) observed in the haze, which coincided with the relatively low backscatter ratio (0.11) and up-scatter fraction (0.23), were related to the increased particle size, and could have had a heating effect on the atmosphere. Aerosols accumulated primarily below 3 km and according to CALIPSO, were regular in their shapes. At the surface, the aerosol extinction coefficient detected by satellite remained at ~1 km−1, very close to the ground-based observations. Aerosol optical properties measured at this downtown site could help further the understanding of the effects of aerosols on the air quality, city environment, and radiation balance.
Highlights
The Intergovernmental Panel on Climate Change has reported that atmospheric aerosol radiative forcing could have significant effect on climate change [1]
Visibility has been adopted as the basic index; because both haze and fog result in reduced visibility, on 1 June 2010, the Chinese Meteorological Administration (CMA) issued a standard for haze observation and forecasting in China
This study has considered haze as conditions where the horizontal visibility is
Summary
The Intergovernmental Panel on Climate Change has reported that atmospheric aerosol radiative forcing could have significant effect on climate change [1]. Aerosols affect Earth’s radiation balance directly by scattering and absorbing solar shortwave and longwave radiation. A long-term study of haze in Nanjing has indicated a rapid increase in the concentration of aerosols with diameters of 0.6–1.4 μm, which has led to a significant growth in the scattering coefficient [12]. In hazy regions, increased amounts of absorbing aerosols, (e.g., dust and black carbon (BC)) can induce anomalous water cycle feedback, which can affect the general circulation and alter the dynamical state of the entire monsoon system [13,14,15]. To further the understanding of the causes and environmental effects of haze episodes in central China, we conducted a comprehensive study in. The vertical distribution of the aerosols was obtained from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite
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