Using single‐scattering albedo spectral curvature to characterize East Asian aerosol mixtures

Li, Jing; Carlson, Barbara E.; Lacis, Andrew A.

doi:10.1002/2014jd022433

Cited by 53 publications

(46 citation statements)

References 72 publications

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“…Based on these parameters, the aerosols can be identified as dust dominated, BC (including biomass burning and urban/industrial aerosols) dominated and other mixed (peak) type aerosols because the curvature probability (or frequency) distributions are different for the different aerosol mixtures. As indicated in Li et al (2015a), the SSA or AAOD curvature is mostly concentrated at approximately 0 for the BC-dominated aerosol mixture, which is much smaller than that of the dust-dominated aerosol mixtures (0.1 for SSA curvature and 0.5-1 for AAOD curvature) over East Asia. Based on their method, the curvatures of SSA and AAOD are calcu- Figure 10.…”

Section: Aerosol Classification Based On Optical Propertiesmentioning

confidence: 89%

“…For biomass burning aerosols, the SSAs decrease monotonically with wavelength. Non-monotonic variations in SSA with changes in wavelength might be due to aerosol mixtures dominated by another type of aerosol, as indicated by Li et al (2015a). They proposed two curvature parameters to provide additional information on the aerosol compositions: the second derivative of the second-order polynomial fit of the SSA and wavelength and the fit of the AAOD and wavelength, as shown in Eqs.…”

Section: Aerosol Classification Based On Optical Propertiesmentioning

confidence: 99%

“…Detailed descriptions were presented by Li et al (2015a). Based on these parameters, the aerosols can be identified as dust dominated, BC (including biomass burning and urban/industrial aerosols) dominated and other mixed (peak) type aerosols because the curvature probability (or frequency) distributions are different for the different aerosol mixtures.…”

Section: Aerosol Classification Based On Optical Propertiesmentioning

confidence: 99%

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The optical properties, physical properties and direct radiative forcing of urban columnar aerosols in the Yangtze River Delta, China

et al. 2018

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Abstract. The optical and physical properties as well as the direct radiative forcings (DRFs) of fractionated aerosols in the urban area of the western Yangtze River Delta (YRD) are investigated with measurements from a Cimel sun photometer combined with a radiation transfer model. Ground-based observations of aerosols have much higher temporal resolutions than satellite retrievals. An initial analysis reveals the characteristics of the optical properties of different types of fractionated aerosols in the western YRD. The total aerosols, mostly composed of scattering components (93.8 %), have mean optical depths of 0.65 at 550 nm and refractive index of 1.44 + 0.0084i at 440 nm. The fine aerosols are approximately four times more abundant and have very different compositions from coarse aerosols. The absorbing components account for only ∼ 4.6 % of fine aerosols and 15.5 % of coarse aerosols and have smaller sizes than the scattering aerosols within the same mode. Therefore, fine particles have stronger scattering than coarse ones, simultaneously reflecting the different size distributions between the absorbing and scattering aerosols. The relationships among the optical properties quantify the aerosol mixing and imply that approximately 15 and 27.5 % of the total occurrences result in dustand black-carbon-dominating mixing aerosols, respectively, in the western YRD. Unlike the optical properties, the size distributions of aerosols in the western YRD are similar to those found at other sites over eastern China on a climatological scale, peaking at radii of 0.148 and 2.94 µm. However, further analysis reveals that the coarse-dominated particles can also lead to severe haze pollution over the YRD. Observation-based estimations indicate that both fine and coarse aerosols in the western YRD exert negative DRFs, and this is especially true for fine aerosols (−11.17 W m −2 at the top of atmosphere, TOA). A higher absorption fraction leads directly to the negative DRF being further offset for coarse aerosols (−0.33 W m −2 ) at the TOA. Similarly, the coarsemode DRF contributes to only 13.3 % of the total scattering aerosols but > 33.7 % to the total absorbing aerosols. A sensitivity analysis states that aerosol DRFs are not highly sensitive to their profiles in clear-sky conditions. Most of the aerosol properties and DRFs have substantial seasonality in the western YRD. The results further reveal the contributions of each component of the different size particles to the total aerosol optical depths (AODs) and DRFs. Additionally, these results can be used to improve aerosol modelling performance and the modelling of aerosol effects in the eastern regions of China.

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Section: Aerosol Classification Based On Optical Propertiesmentioning

confidence: 89%

Section: Aerosol Classification Based On Optical Propertiesmentioning

confidence: 99%

Section: Aerosol Classification Based On Optical Propertiesmentioning

confidence: 99%

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The optical properties, physical properties and direct radiative forcing of urban columnar aerosols in the Yangtze River Delta, China

et al. 2018

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“…It is worth noting that the SSA in Qiandaohu may be not typical due to only few available inversion data from AERONET in most months. Overall, for most sites, the variations of the SSA show a larger dependence on wavelength in winter and spring but a smaller dependence in summer and fall, which can caused by a mixture of anthropogenic aerosols and coarse dust in winter and spring [31]. Large daily variations in the SSA also exist in Beijing and Hongkong, where regional transport usually superposes on local pollution.…”

Section: Aerosol Optical Properties In Eastern Chinamentioning

confidence: 99%

How Do Aerosol Properties Affect the Temporal Variation of MODIS AOD Bias in Eastern China?

et al. 2017

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Abstract:The rapid changes of aerosol sources in eastern China during recent decades could bring considerable uncertainties for satellite retrieval algorithms that assume little spatiotemporal variation in aerosol single scattering properties (such as single scattering albedo (SSA) and the size distribution for fine-mode and coarse mode aerosols) in East Asia. Here, using ground-based observations in six AERONET sites, we characterize typical aerosol optical properties (including their spatiotemporal variation) in eastern China, and evaluate their impacts on Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 6 aerosol retrieval bias. Both the SSA and fine-mode particle sizes increase from northern to southern China in winter, reflecting the effect of relative humidity on particle size. The SSA is~0.95 in summer regardless of the AEROENT stations in eastern China, but decreases to 0.85 in polluted winter in northern China. The dominance of larger and highly scattering fine-mode particles in summer also leads to the weakest phase function in the backscattering direction. By focusing on the analysis of high aerosol optical depth (AOD) (>0.4) conditions, we find that the overestimation of the AOD in Dark Target (DT) retrieval is prevalent throughout the whole year, with the bias decreasing from northern China, characterized by a mixture of fine and coarse (dust) particles, to southern China, which is dominated by fine particles. In contrast, Deep Blue (DB) retrieval tends to overestimate the AOD only in fall and winter, and underestimates it in spring and summer. While the retrievals from both the DT and DB algorithms show a reasonable estimation of the fine-mode fraction of AOD, the retrieval bias cannot be attributed to the bias in the prescribed SSA alone, and is more due to the bias in the prescribed scattering phase function (or aerosol size distribution) in both algorithms. In addition, a large yearly change in aerosol single scattering properties leads to correspondingly obvious variations in the time series of MODIS AOD bias. Our results reveal that the aerosol single scattering properties in the MODIS algorithm are insufficient to describe a large variation of aerosol properties in eastern China (especially change of particle size), and can be further improved by using newer AERONET data.

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“…Additionally, some authors have noted that AAE is not necessarily constant throughout the visible and near-infrared wavelengths at East Asian AERONET sites; Eck et al, 2010;Li et al, 2015). The spectral dependence of absorption (i.e., AAE) depends upon particle size and the imaginary refractive index, and excellent overviews of the relationship between AAE and aerosol microphysics are provided by Moosmüller et al (2009Moosmüller et al ( , 2011.…”

Section: G L Schuster Et Al: Understanding the Aae For Remote Sensmentioning

confidence: 99%

Remote sensing of soot carbon – Part 2: Understanding the absorption Ångström exponent

et al. 2016

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Abstract. Recently, some authors have suggested that the absorption Ångström exponent (AAE) can be used to deduce the component aerosol absorption optical depths (AAODs) of carbonaceous aerosols in the AERONET database. This AAE approach presumes that AAE 1 for soot carbon, which contrasts the traditional small particle limit of AAE = 1 for soot carbon. Thus, we provide an overview of the AERONET retrieval, and we investigate how the microphysics of carbonaceous aerosols can be interpreted in the AERONET AAE product. We find that AAE 1 in the AERONET database requires large coarse mode fractions and/or imaginary refractive indices that increase with wavelength. Neither of these characteristics are consistent with the current definition of soot carbon, so we explore other possibilities for the cause of AAE 1. AAE is related to particle size, and coarse mode particles have a smaller AAE than fine mode particles for a given aerosol mixture of species. We also note that the mineral goethite has an imaginary refractive index that increases with wavelength, is very common in dust regions, and can easily contribute to AAE 1. We find that AAE 1 can not be caused by soot carbon, unless soot carbon has an imaginary refractive index that increases with wavelength throughout the visible and near-infrared spectrums. Finally, AAE is not a robust parameter for separating carbonaceous absorption from dust aerosol absorption in the AERONET database.

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Using single‐scattering albedo spectral curvature to characterize East Asian aerosol mixtures

Cited by 53 publications

References 72 publications

The optical properties, physical properties and direct radiative forcing of urban columnar aerosols in the Yangtze River Delta, China

The optical properties, physical properties and direct radiative forcing of urban columnar aerosols in the Yangtze River Delta, China

How Do Aerosol Properties Affect the Temporal Variation of MODIS AOD Bias in Eastern China?

Remote sensing of soot carbon – Part 2: Understanding the absorption Ångström exponent

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