Light-absorbing aerosol properties retrieved from the sunphotometer observation over the Yangtze River Delta, China

Wang, Jing; Niu, Shengjie; Xu, Dongmei

doi:10.1364/ao.57.000992

Cited by 7 publications

(1 citation statement)

References 62 publications

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“…Yearly calibrations of the instruments ensure the accuracy of the measurements [22]. Detailed information on the sun photometer characteristics, operational procedures, data processing, and retrieval method are available from the AERONET website (https://aeronet.gsfc.nasa.gov/); detail on the NUIST sun photometer procedures and a data overview is provided by Wang et al [43]. The time periods studied were two episodes, one in the summer and one in the winter of 2017, selected from the observations, as described in Section 3.1.…”

Section: Observational Datamentioning

confidence: 99%

Contrasting Aerosol Optical Characteristics and Source Regions During Summer and Winter Pollution Episodes in Nanjing, China

et al. 2019

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Two episodes with heavy air pollution in Nanjing, China, one in the summer and another one in the winter of 2017, were selected to study aerosol properties using sun photometer and ground-based measurements, together with source region analysis. The aerosol properties, the meteorological conditions, and the source regions during these two episodes were very different. The episodes were selected based on the air quality index (AQI), which reached a maximum value of 193 during the summer episode (26 May–3 June) and 304 during the winter episode (21–31 December). The particulate matter (PM) concentrations during the winter episode reached maximum values for PM2.5/10 of 254 g m−3 and 345 g m−3, much higher than those during the summer (73 and 185 g m−3). In contrast, the value of aerosol optical depth (AOD) at 500 nm was higher during the summer episode (2.52 0.19) than during that in the winter (1.38 0.18). A high AOD value does not necessarily correspond to a high PM concentration but is also affected by factors, such as wind, Planetary Boundary Layer Height (PBLH), and relative humidity. The mean value of the Ångström Exponent (AE) varied from 0.91–1.42, suggesting that the aerosol is a mixture of invaded dust and black carbon. The absorption was stronger during the summer than during the winter, with a minimum value of the single scattering albedo (SSA) at 440 nm of 0.86 on 28 May. Low values of asymmetry factor (ASY) (0.65 at 440 nm and 0.58 at 1020 nm) suggest a large number of anthropogenic aerosols, which are absorbing fine-mode particles. The Imaginary part of the Refractive Index (IRI) was higher during the summer than during the winter, indicating there was absorbing aerosol during the summer. These differences in aerosol properties during the summer and winter episodes are discussed in terms of meteorological conditions and transport. The extreme values of PM and AOD were reached during both episodes in conditions with stable atmospheric stratification and low surface wind speed, which are conducive for the accumulation of pollutants. Potential source contribution function (PSCF) and concentration weighted trajectory (CWT) analysis show that fine mode absorbing aerosols dominate during the summer season, mainly due to emissions of local and near-by sources. In the winter, part of the air masses was arriving from arid/semi-arid regions (Shaanxi, Ningxia, Gansu, and Inner Mongolia provinces) covering long distances and transporting coarse particles to the study area, which increased the scattering characteristics of aerosols.

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Section: Observational Datamentioning

confidence: 99%