Column-integrated aerosol optical properties and direct radiative forcing over the urban-industrial megacity Nanjing in the Yangtze River Delta, China

• Published in: Environmental science and pollution research international 2016-09, Vol.23 (17), p.17532-17552
• Main Authors: Kang, Na, Kumar, K. Raghavendra, Yu, Xingna, Yin, Yan
• Format: Article
• Language: English
• Subjects: Aerosols; Aerosols - analysis; Albedo; Aquatic Pollution; Atmosphere; Atmospheric aerosols; Atmospheric Protection/Air Quality Control/Air Pollution; Autumn; Black carbon; China; Climate change; Dust; Dust - analysis; Earth and Environmental Science; Economic development; Ecotoxicology; Efficiency; Environment; Environmental Chemistry; Environmental Health; Environmental science; Laboratories; Megacities; Optical analysis; Optical properties; Outdoor air quality; Precipitation; Radiation; Radiative transfer; Regions; Remote sensing; Research Article; Rivers; Rivers - chemistry; Solar radiation; Spring; Studies; Summer; Waste Water Technology; Water Management; Water Pollution Control
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-016-6953-1

Aerosol optical properties were measured and analyzed through the ground-based remote sensing Aerosol Robotic Network (AERONET) over an urban-industrial site, Nanjing (32.21° N, 118.72° E, and 62 m above sea level), in the Yangtze River Delta, China, during September 2007–August 2008. The annual averaged values of aerosol optical depth (AOD 500 ) and the Ångström exponent (AE 440–870 ) were measured to be 0.94 ± 0.52 and 1.10 ± 0.21, respectively. The seasonal averaged values of AOD 500 (AE 440–870 ) were noticed to be high in summer (autumn) and low in autumn (spring). The characterization of aerosol types showed the dominance of mixed type followed by the biomass burning and urban-industrial type of aerosol at Nanjing. Subsequently, the curvature ( a 2 ) obtained from the second-order polynomial fit and the second derivative of AE ( α ′) were also analyzed to understand the dominant aerosol type. The single scattering albedo at 440 nm (SSA 440 ) varied from 0.88 to 0.93 with relatively lower (higher) values during the summer (spring), suggesting an increase in black carbon and mineral dust (desert dust) aerosols of absorbing (scattering) nature. The averaged monthly and seasonal evolutions of shortwave (0.3–4.0 μm) direct aerosol radiative forcing (DARF) values were computed from the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model both at the top of atmosphere (TOA) and bottom of atmosphere (SUR) during the study period. Further, the aerosol forcing efficiency (AFE) and the corresponding atmospheric heating rates (AHR) were also estimated from the forcing within the atmosphere (ATM). The derived DARF values, therefore, produced a warming effect within the atmosphere due to strong absorption of solar radiation.