A shape model of internally mixed soot particles derived from artificial surface tension

Ishimoto, Hiroshi; Kudo, Rei; Adachi, Kouji

doi:10.5194/amt-12-107-2019

Cited by 30 publications

(30 citation statements)

References 56 publications

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“…In the past, many studies have used simpler or more complicated particle shape models in order to reproduce the lidar measurements of smoke. In Kahnert (2017), the PLDR of black carbon aggregates covered by a coating of sulfates was simulated by two different models: a closed cell model (i.e. each monomer in the aggregate is coated separately) and a coated aggregate model (i.e.…”

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confidence: 99%

Is the near-spherical shape the “new black” for smoke?

et al. 2020

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Abstract. We examine the capability of near-spherical-shaped particles to reproduce the triple-wavelength particle linear depolarization ratio (PLDR) and lidar ratio (LR) values measured over Europe for stratospheric smoke originating from Canadian wildfires. The smoke layers were detected both in the troposphere and the stratosphere, though in the latter case the particles presented PLDR values of almost 18 % at 532 nm as well as a strong spectral dependence from the UV to the near-IR wavelength. Although recent simulation studies of rather complicated smoke particle morphologies have shown that heavily coated smoke aggregates can produce large PLDR, herein we propose a much simpler model of compact near-spherical smoke particles. This assumption allows for the reproduction of the observed intensive optical properties of stratospheric smoke, as well as their spectral dependence. We further examine whether an extension of the current Aerosol Robotic Network (AERONET) scattering model to include the near-spherical shapes could be of benefit to the AERONET retrieval for stratospheric smoke cases associated with enhanced PLDR. Results of our study illustrate the fact that triple-wavelength PLDR and LR lidar measurements can provide us with additional insight when it comes to particle characterization.

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confidence: 99%

Is the near-spherical shape the “new black” for smoke?

et al. 2020

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“…The calculated LPDR of the fractal soot aggregate at 355, 532 and 1064 nm are presented in Table 2 for m = 1.42 + i0.02. Although the use of this simple fractal geometry provides significantly large PLDR, it does not reproduce the measured values of both PLDR and LR, as it was also shown in greater detail in [2] (see Fig. 9 and 10).…”

Section: Figure 1 Presents the Observations From Leipzig On 22mentioning

confidence: 85%

“…9 and 10). In order to reproduce the measurements for aged smoke particles the fractals need to be coated by other material, producing a shape that closely resembles the near-spherical shape, as shapes for Type-B, size 11, Vr = 20, found in [2], Fig. 4.…”

Section: Figure 1 Presents the Observations From Leipzig On 22mentioning

confidence: 99%

Is Near-Spherical Shape “the New Black” for Smoke ?

et al. 2020

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We present smoke lidar measurements from the Canadian fires of 2017. The advected smoke layers over Europe are detected at both tropospheric and stratospheric heights, with the latter presenting non-typical values of the Particle Linear Depolarization Ratio (PLDR) with strong wavelength dependence from the UV to the Near-IR. Specifically, the PLDR values are of the order of 22, 18 and 4% at 355, 532 and 1064 nm respectively. In an attempt to interpret these results, we apply the hypothesis that smoke particles have near-spherical shapes. Scattering calculations with the T-matrix code support other findings in the literature ([1]- [2]), showing that the near-spherical shape (or closely similar shapes as in [2]), is the only shape that has been shown to reproduce the observed PLDR and Lidar Ratio (LR) values of the stratospheric smoke particles at the three measurement wavelengths.

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“…MRI v2 uses the same randomly oriented spheroid model with a fixed aspect ratio distribution as the AERONET, but it is shown that the inconsistencies in the spectral variabilities of the lidar ratio and depolarization ratio of dust particles between the lidar and AERONET sun photometer data, in particular, in the near ultraviolet wavelength range (Müller et al, 2010). Recently, the various realistic particle models are developed for 650 dust (e.g., Ishimoto et al, 2010;Gasteiger et al, 2011), soot (e.g., Kahnert et al, 2013;Ishimoto et al, 2019), and volcanic ash (e.g., Lindqvist et al, 2011). The application of these models to the sky radiometer and lidar data would improve the remote sensing of aerosols.…”

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confidence: 99%

Optimal use of Prede POM sky radiometer for aerosol, water vapor, and ozone retrievals

Kudo¹,

Diémoz²,

Estellés³

et al. 2020

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Abstract. The Prede POM sky radiometer is a filter radiometer deployed worldwide in the SKYNET international network. A new method called, Skyrad pack MRI version 2 (MRI v2), is here presented, to retrieve aerosol properties (size distribution, real and imaginary parts of the refractive index, single-scattering albedo, asymmetry factor, lidar ratio, and linear depolarization ratio), and water vapor and ozone column concentrations from the sky radiometer measurements. MRI v2 overcomes two limitations of previous methods (Skyrad pack versions 4.2 and 5, and MRI version 1). One is the use of all the wavelengths of 315, 340, 380, 400, 500, 675, 870, 940, 1020, 1627, and 2200 nm, if available from the sky radiometers, for example, in POM-02 models. The previous methods cannot use the wavelengths of 315, 940, 1627, and 2200 nm. This enables us to provide improved estimates of the aerosol optical properties, covering almost all the wavelengths of solar radiation. The other is the use of measurements in the principal plane geometry in addition to the solar almucantar plane geometry that is used in the previous versions. The measurements in the principal plane are regularly performed, however they are currently not exploited despite being useful in the case of small solar zenith angles, when the scattering angle distribution for almucantars becomes too small to yield useful information. Moreover, in the inversion algorithm, MRI v2 optimizes the smoothness constraints of the spectral dependencies of the refractive index and size distribution, and changes the contribution of the diffuse radiances to the cost function according to the aerosol optical depth. These overcome issues with the estimation of the size distribution and single-scattering albedo in the Skyrad pack version 4.2. The scattering model used here allows for non-spherical particles, improving results for mineral dust and permitting to evaluate the depolarization ratio. An assessment of the retrieval uncertainties using synthetic measurement show that best performance is obtained when the aerosol optical depths is larger than 0.2 at 500 nm. Improvements over the Skyrad pack versions 4.2 and 5 are obtained for the retrieved size distribution, imaginary part of the refractive index, single-scattering albedo, and lidar ratio at Tsukuba, Japan, while yielding comparable retrievals of the aerosol optical depth, real part of the refractive index, and asymmetry factor. A radiative closure study using surface solar irradiances from Baseline Surface Radiation Network and the parameters retrieved from MRI v2 showed consistency, with a positive bias of the simulated global irradiance, about +24 Wm−2 (+3 %). Furthermore, the MRI v2 retrievals of the refractive index, single-scattering albedo, asymmetry factor, and size distribution have been found in agreement with integrated profiles of aircraft in-situ measurements of two Saharan dust events at the Cape Verde archipelago, during the SAVEX-D 2015 field campaign.

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A shape model of internally mixed soot particles derived from artificial surface tension

Cited by 30 publications

References 56 publications

Is the near-spherical shape the “new black” for smoke?

Is the near-spherical shape the “new black” for smoke?

Is Near-Spherical Shape “the New Black” for Smoke ?

Optimal use of Prede POM sky radiometer for aerosol, water vapor, and ozone retrievals

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