Ultraviolet and visible imaginary refractive index of strongly absorbing atmospheric particulate matter

Gillespie, James B.; Lindberg, James D.

doi:10.1364/ao.31.002112

Cited by 41 publications

(40 citation statements)

References 3 publications

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“…The annual average SSA (440 nm) of MQ is 0.87 ± 0.06, smaller than other reported measurements of desert dust sites (mostly larger than 0.90) [20,65], illustrating the strong absorptivity of this site. We primarily attribute this to the absorbing aerosols from anthropogenic sources in Minqin County [36], especially in summer, as well as the higher content level of absorbing hematite [66] or other iron oxides in the dust aerosol at this site [67]. We also find decreasing SSA spectra at MQ, similar to previous research at this site (e.g., [36]), and this can be attributed to the existence of fine particles.…”

Section: Single Scattering Albedosupporting

confidence: 81%

Aerosol Optical and Microphysical Properties of Four Typical Sites of SONET in China Based on Remote Sensing Measurements

Xie

et al. 2015

Remote Sensing

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Abstract:The current understanding of columnar aerosol optical and microphysical properties of different regions and seasons in China is insufficient due to the lack of measurements. Aiming to improve descriptions of aerosol models over China, this paper presents a systematic aerosol characterization of different sites based on a newly developed remote sensing network for aerosol observation, the Sun-sky radiometer Observation NETwork (SONET). One year of ground-based solar and sky radiation measurements of four typical sites of SONET (Beijing-urban-industrial site, Zhangye-rural site, Minqin-desert site, Zhoushan-oceanic site) are used to retrieve aerosol properties using similar inversion algorithms with AErosol RObotic NETwork (AERONET), including aerosol optical depth, Ångström exponent, volume size distribution, complex refractive index, single scattering albedo, and percentage of spherical particles. The retrieved properties among sites and seasons are found to be different in terms of magnitude, spectral dependence, and partition of fine and coarse mode, which can be primarily explained by different aerosol composition and mixing states that closely relate to the local climate, the natural environment, and most importantly, the ubiquitous anthropogenic impacts. For example, large dust particles greatly contribute to the low fine mode fraction in both volume concentration and optical depth for the Minqin site through the entire year, while abundant small particles that mainly come from emission sources dominate the size distribution and OPEN ACCESS Remote Sens. 2015, 7 9929 light extinction of aerosol in the summer at the Beijing site. The results also show general agreements with other studies on the aerosol properties at each site, however, some unique features are still noticeable, especially at the desert site and oceanic site (e.g., the unusually strong aerosol absorptivity indicated by the large imaginary refractive index and low single scattering albedo at the Minqin and Zhoushan sites), which can be partly attributed to the existence of absorbing particles coming from anthropogenic sources.

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Section: Single Scattering Albedosupporting

confidence: 81%

Aerosol Optical and Microphysical Properties of Four Typical Sites of SONET in China Based on Remote Sensing Measurements

Xie

et al. 2015

Remote Sensing

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“…The disparity between the laboratory and remotely sensed values of w 0 is interesting. Pure mineral dust should not absorb appreciably above 0.55 mm [Gillespie and Lindberg, 1992;Sokolik and Toon, 1999], suggesting that black carbon, a frequent component of desert aerosols [Hansen et al, 1993;Levin et al, 1980], may have been present in the laboratory samples. Alternatively, hematite, a naturally occurring iron oxide that absorbs strongly in the visible and near-infrared [Sokolik and Toon, 1999], could have been present in significantly greater quantities in the dust samples.…”

Section: Discussionmentioning

confidence: 99%

Columnar aerosol single‐scattering albedo and phase function retrieved from sky radiance over the ocean: Measurements of Saharan dust

2003

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[1] The single-scattering albedo and phase function of African mineral dust are retrieved at 14 wavelengths across the visible spectrum from ground-based measurements of the aerosol optical thickness and the sky radiance taken in the solar principal plane. The retrieval algorithm employs the radiative transfer equation to solve by iteration for these properties that best reproduce the observed sky radiance, and is therefore independent of particle shape. The estimated error in the retrieved single-scattering albedo is less than 0.02 due to the precision of the solar-reflectance-based calibration of the radiometer. The phase function retrieved at 860 nm is robust under simulations of expected experimental errors and may be used to characterize aerosol scattering at the directly measured scattering angles (i.e., Â 155°). The phase function retrieved at 443 nm, however, is too sensitive to such errors to confidently describe the angular scattering at blue wavelengths. The single-scattering albedo displays a spectral shape expected of iron-bearing minerals but is much higher than climate models have assumed, indicating that wind-blown mineral dust cools Earth more than is generally believed. The method may be applied to any combination of airborne and ground-based measurements over the ocean and can complement more involved ground-based retrievals through its insensitivity to particle shape and ability to retrieve aerosol properties at relatively small aerosol optical depths.INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 1640 Global Change: Remote sensing; 1694 Global Change: Instruments and techniques; 4275 Oceanography: General: Remote sensing and electromagnetic processes (0689); KEYWORDS: aerosol, mineral dust, absorption, sky radiance, scattering, optical properties Citation: Cattrall, C., K. L. Carder, and H. R. Gordon, Columnar aerosol single-scattering albedo and phase function retrieved from sky radiance over the ocean: Measurements of Saharan dust,

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“…Optical parameters (e.g., τ and τ a ) of aerosols are usually sensitive to the size distribution and less sensitive to the refractive indices Gobbi et al, 2007). Therefore, the separation of aerosol VPSD is the basis for the next steps of accurate estimation of sub-CRIs.…”

Section: Size Distribution Breakdownmentioning

confidence: 99%

Estimation of aerosol complex refractive indices for both fine and coarse modes simultaneously based on AERONET remote sensing products

Zhang

et al. 2017

Atmos. Meas. Tech.

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Abstract. Climate change assessment, especially model evaluation, requires a better understanding of complex refractive indices (CRIs) of atmospheric aerosols -separately for both fine and coarse modes. However, the widely used aerosol CRI obtained by the global Aerosol Robotic Network (AERONET) corresponds to total-column aerosol particles without separation for fine and coarse modes. This paper establishes a method to separate CRIs of fine and coarse particles based on AERONET volume particle size distribution (VPSD), aerosol optical depth (AOD) and absorbing AOD (AAOD). The method consists of two steps. First a multimodal log-normal distribution that best approximates the AERONET VPSD is found. Then the fine and coarse mode CRIs are found by iterative fitting of AERONET AODs to Mie calculations. The numerical experiment shows good performance for typical water-soluble, biomass burning and dust aerosol types, and the estimated uncertainties on the retrieved sub-mode CRIs are about 0.11 (real part) and 78 % (imaginary part). The 1-year measurements at the AERONET Beijing site are processed, and we obtain CRIs of 1.48-0.010i (imaginary part at 440 nm is 0.012) for fine mode particles and 1.49-0.004i (imaginary part at 440 nm is 0.007) for coarse mode particles, for the period of 2014-2015. Our results also suggest that both fine and coarse aerosol mode CRIs have distinct seasonal characteristics; in particular, CRIs of fine particles in winter season are significantly higher than summer due to possible anthropogenic influences.

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Ultraviolet and visible imaginary refractive index of strongly absorbing atmospheric particulate matter

Cited by 41 publications

References 3 publications

Aerosol Optical and Microphysical Properties of Four Typical Sites of SONET in China Based on Remote Sensing Measurements

Aerosol Optical and Microphysical Properties of Four Typical Sites of SONET in China Based on Remote Sensing Measurements

Columnar aerosol single‐scattering albedo and phase function retrieved from sky radiance over the ocean: Measurements of Saharan dust

Estimation of aerosol complex refractive indices for both fine and coarse modes simultaneously based on AERONET remote sensing products

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