Optical Modeling of Black Carbon With Different Coating Materials: The Effect of Coating Configurations

Luo, Jie; Zhang, Qixing; Luo, Jianfei; Liu, Jia; Huo, Yinuo; Zhang, Yongming

doi:10.1029/2019jd031701

Cited by 39 publications

(26 citation statements)

References 107 publications

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“…However, as coating materials increase, the fractal structure of BC may be damaged. Chakrabarty and Heinson [71] used a complex BC model by assuming that coating materials surround BC to calculate BC optical properties; Ishimoto et al [72] proposed an internally mixed BC model based on the artificial surface tension; Luo et al [48] have proposed BC models with different coating materials. However, these models are complex and computationally expensive.…”

Section: Generation Of Bcmentioning

confidence: 99%

The Ångström Exponent and Single-Scattering Albedo of Black Carbon: Effects of Different Coating Materials

Luo

Zhang

2020

Atmosphere

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In this work, the absorption Ångström exponent (AAE), extinction Ångström exponent (EAE), and single-scattering albedo (SSA) of black carbon (BC) with different coating materials are numerically investigated. BC with different coating materials can provide explanations for the small AAE, small EAE ,and large AAE observed in the atmosphere, which is difficult to be explained by bare BC aggregate models. The addition of organic carbon (OC) does not necessarily increase AAE due to the transformation of BC morphologies and the existence of non-absorbing OC. The addition of coating materials does also not necessarily decrease EAE. While the addition of coating materials can increase the total size of BC-containing particles, the effective refractive index can be modified by introducing the coating materials, so increases the EAE. We found that it is not possible to differentiate between thinly- and heavily-coated BC based on EAE or AAE alone. On the other hand, SSA is much less sensitive to the size and can provide much more information for distinguishing heavily-coated BC from thinly-coated BC. For BC with different coating materials and mixing states, AAE, EAE, and SSA show rather different sensitivities to particle size and composition ratios, and their spectral-dependences also exhibit distinct differences. Different AAE and EAE trends with BC/OC ratio were also found for BC with different coating materials and mixing states. Furthermore, we also found empirical fittings for AAE, EAE, SSA, and optical cross-sections, which may be useful for retrieving the size information based on the optical measurements.

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Section: Generation Of Bcmentioning

confidence: 99%

The Ångström Exponent and Single-Scattering Albedo of Black Carbon: Effects of Different Coating Materials

Luo

Zhang

2020

Atmosphere

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“…Lidar ratios and depolarization ratios measured simultaneously at both 355 and 532 nm wavelengths are a prerequisite in efforts to successfully homogenize the overall Aeolus-CALIPSO data set of smoke optical properties later on. Simultaneously measured lidar ratios and depolarization ratios are also important parameters in aerosol typing efforts (see, e.g., Burton et al, 2012Burton et al, , 2015Groß et al, 2013;Nicolae et al, 2018;Papagiannopoulos et al, 2018) with lidars from ground and in space to improve optical models developed to simulate the smoke optical properties as a function of particle shape and size characteristics and composition (e.g., Kahnert, 2017;Mishchenko, 2018, 2020;Luo et al, 2019;Gialitaki et al, 2020). Thus, our Punta Arenas lidar observations in January 2020 can be regarded as an important contribution to the global library of aerosol optical properties.…”

Section: Introductionmentioning

confidence: 99%

Smoke of extreme Australian bushfires observed in the stratosphere over Punta Arenas, Chile, in January 2020: optical thickness, lidar ratios, and depolarization ratios at 355 and 532 nm

et al. 2020

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Abstract. We present particle optical properties of stratospheric smoke layers observed with multiwavelength polarization Raman lidar over Punta Arenas (53.2∘ S, 70.9∘ W), Chile, at the southernmost tip of South America in January 2020. The smoke originated from the record-breaking bushfires in Australia. The stratospheric aerosol optical thickness reached values up to 0.85 at 532 nm in mid-January 2020. The main goal of this rapid communication letter is to provide first stratospheric measurements of smoke extinction-to-backscatter ratios (lidar ratios) and particle linear depolarization ratios at 355 and 532 nm wavelengths. These aerosol parameters are important input parameters in the analysis of spaceborne CALIPSO and Aeolus lidar observations of the Australian smoke spreading over large parts of the Southern Hemisphere in January and February 2020 up to heights of around 30 km. Lidar and depolarization ratios, simultaneously measured at 355 and 532 nm, are of key importance regarding the homogenization of the overall Aeolus (355 nm wavelength) and CALIPSO (532 nm wavelength) lidar data sets documenting the spread of the smoke and the decay of the stratospheric perturbation, which will be observable over the entire year of 2020. We found typical values and spectral dependencies of the lidar ratio and linear depolarization ratio for aged stratospheric smoke. At 355 nm, the lidar ratio and depolarization ratio ranged from 53 to 97 sr (mean 71 sr) and 0.2 to 0.26 (mean 0.23), respectively. At 532 nm, the lidar ratios were higher (75–112 sr, mean 97 sr) and the depolarization ratios were lower with values of 0.14–0.22 (mean 0.18). The determined depolarization ratios for aged Australian smoke are in very good agreement with respective ones for aged Canadian smoke, observed with lidar in stratospheric smoke layers over central Europe in the summer of 2017. The much higher 532 nm lidar ratios, however, indicate stronger absorption by the Australian smoke particles.

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“…R c = 50R g and R c = R g were assumed to represent the film and spherical coatings, and are named Model B and Model C, respectively. In our previous study (Luo et al, 2019), we have demonstrated that our proposed models can greatly simulate the internally mixed BC morphologies and reproduce the measured absorption as well. For more details about the algorithm to generate the coated BC, please refer to Luo et al (2019), and the typically generated morphologies are shown in Figure 2 and the Figures S1-S2 of Luo et al (2019).…”

Section: Morphologiesmentioning

confidence: 71%

“…Non-spherical aerosol models show more excellent performance on reproducing the measurements even though Mie theory was commonly used in remote sensing and climate modeling (Bi et al, 2018;He et al, 2016He et al, , 2015Chakrabarty et al, 2007;Luo et al, 2019). In the atmosphere, BC can be mixed with BrC, and the mixing states are commonly divided into externally mixed and internally mixed.…”

Section: Morphologiesmentioning

confidence: 99%

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Effects of black carbon morphology on the brown carbon absorption estimation: from numerical aspects

Luo¹,

Zhang²,

Zhang³

2020

Preprint

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Abstract. In this work, we developed a numerical method to investigate the effects of black carbon morphology on the estimation of brown carbon (BrC) absorption using the Absorption Ångström exponent (AAE) method. Pseudo measurements of the total absorption were generated based on several morphologically mixed black carbon (BC) models, then the BrC absorption was inferred based on different AAE methods. By comparing the estimated BrC absorption with True BrC absorption, we found that both AAE = 1 and Mie AAE methods do not provide accurate estimation for the BrC absorption, and the estimated BrC absorption can deviate several times from True BrC absorption. The newly proposed Wavelength Dependent AAE (WDA) method does not necessarily improve the estimations, sometimes it may even provide worse estimations than the AAE = 1 and Mie AAE methods. Fixing the fractal dimension to be 1.8, the deviation between the estimated BrC mass absorption cross-section (MAC) and True BrC MAC can reach approximately 9 m2/g, which is far more than brown carbon MAC itself. Therefore, the estimation of BrC absorption based on the AAE method should carefully consider the morphological effects of BC. Our findings highlight the BC morphological effects on the BrC absorption estimation.

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Optical Modeling of Black Carbon With Different Coating Materials: The Effect of Coating Configurations

Cited by 39 publications

References 107 publications

The Ångström Exponent and Single-Scattering Albedo of Black Carbon: Effects of Different Coating Materials

The Ångström Exponent and Single-Scattering Albedo of Black Carbon: Effects of Different Coating Materials

Smoke of extreme Australian bushfires observed in the stratosphere over Punta Arenas, Chile, in January 2020: optical thickness, lidar ratios, and depolarization ratios at 355 and 532 nm

Effects of black carbon morphology on the brown carbon absorption estimation: from numerical aspects

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