Determination of refractive index for absorbing spheres

Woo, Chang Gyu; You, Sukbeom; Lee, Jeong-Hoon

doi:10.1016/j.ijleo.2013.03.083

Cited by 4 publications

(3 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Improving the knowledge of aerosol CRIs is of great interests to decrease the uncertainties associated with aerosols in the climate change assessment (Boucher et al, 2013). Since the 20th century, direct measurement approaches of CRIs of small particles have been developed in the laboratory (e.g., Woo et al, 2013;Mogo et al, 2012;Marley et al, 2001;Patterson et al, 1977;Volz, 1973). As to aerosol particles in the real atmosphere, many studies retrieved CRIs of nearground-surface aerosols (e.g., Kostenidou et al, 2007;Malloy et al, 2009;Dinar et al, 2006;McMurry et al, 2002) through in situ measurements of particle size distribution as well as scattering and absorption coefficients.…”

Section: Introductionmentioning

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.

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

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.

View full text Add to dashboard Cite

show abstract

“…However, for nigrosin, both n and k are wavelength dependent [21, 85], limiting the applicability of some values in the present investigation. Values for m retrieved at similar λ in the literature were 1.77 + 0.27i at λ = 652 nm [32], 1.7 + 0.24i at λ = 670 nm [91] and 1.70 (± 0.02) + 0.28 (± 0.01) i [21] and 1.812 (± 0.0068) + 0.2461 (± 0.0031) i [85] at λ = 660. Radney and Zangmeister (2015) [21] measured an average ρ eff for nigrosin of 1.34 g cm −3 which is 9 % and 11 % lower than the ρ eff measured for the D geo = 115 and 128 nm data sets, respectively.…”

Section: Resultsmentioning

confidence: 99%

Comparing aerosol refractive indices retrieved from full distribution and size- and mass-selected measurements

Radney¹,

Zangmeister²

2018

Journal of Quantitative Spectroscopy and Radiative Transfer

View full text Add to dashboard Cite

Refractive index retrievals (also termed inverse Mie methods or optical closure) have seen considerable use as a method to extract the refractive index of aerosol particles from measured optical properties. Retrievals of an aerosol refractive index use one of two primary methods: 1) measurements of the extinction, absorption and/or scattering cross-sections or efficiencies of size- (and mass-) selected particles for mass-mobility refractive index retrievals (MM-RIR) or 2) measurements of aerosol size distributions and a combination of the extinction, absorption and/or scattering coefficients for full distribution refractive index retrievals (FD-RIR). These two methods were compared in this study using pure and mixtures of ammonium sulfate (AS) and nigrosin aerosol, which constitute a non-absorbing and absorbing material, respectively. The results indicate that the retrieved complex refractive index values are correlated to the amount of nigrosin in the aerosol but can be highly variable with differences in the real and imaginary components that range between −0.002 and 0.216 and −0.013 and 0.086; the average and standard deviation of the differences are 0.046 ± 0.046 and 0.023 ± 0.033, respectively. Forward calculation of the optical properties yielded average absolute values of the relative deviation of ≈ 15 % and ≈ 26 % for FD-RIR data using the MM-RIR values and contrariwise. The range of retrieved refractive indices were used to calculate the normalized global average aerosol radiative forcing of a model accumulation mode remote continental aerosol. Deviations using the refractive indices of the pure materials range from 9 % to 32 % for AS and 27 % to 45 % for nigrosin. For mixtures of nigrosin and AS, deviations were all > 100 % and not always able to capture the correct direction of the forcing; i.e., positive versus negative.

show abstract

“…Methods for the direct measurement of aerosol m values in the laboratory have been developed since the 20th century [3,10,21,22]. Although direct measurement techniques can be applied to obtain m values and improve our understanding of the differences between the values for fine-and coarse-mode particles, they are not suitable for large-scale application owing to their high cost and low efficiency.…”

Section: Introductionmentioning

confidence: 99%

Inferring Fine-Mode and Coarse-Mode Aerosol Complex Refractive Indices from AERONET Inversion Products over China

et al. 2019

View full text Add to dashboard Cite

Detailed knowledge of the complex refractive indices (m) of fine- and coarse-mode aerosols is important for enhancing understanding of the effect of atmospheric aerosol on climate. However, studies on obtaining aerosol modal m values are particularly scarce. This study proposes a method for inferring m values of fine- and coarse-mode aerosol using the inversion products from the AERONET ground-based aerosol robotic network. By identifying the aerosol type, modal m values are constrained and then inferred based on a maximum likelihood method. Numerical tests showed that compared with the reference values, our method slightly overestimates the real parts of the refractive indices (n), but underestimates the imaginary parts (k) by 2.11% ± 11.59% and 8.4% ± 26.42% for fine and coarse modes, respectively. We applied this method to 21 AERONET sites around China, which yielded annual mean m values of (1.45 ± 0.04) + (0.0109 ± 0.0046)i and (1.53 ± 0.01) + (0.0039 ± 0.0011)i for fine- and coarse-mode aerosols, respectively. It is observed that the fine mode n decreased from 1.53 to 1.39 with increasing latitude, while fine mode k values were generally larger than 0.008 over most of China. The coarse-mode n and k ranged from 1.52 to 1.56 and from 0.002 to 0.006, respectively.

show abstract

Determination of refractive index for absorbing spheres

Cited by 4 publications

References 14 publications

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

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

Comparing aerosol refractive indices retrieved from full distribution and size- and mass-selected measurements

Inferring Fine-Mode and Coarse-Mode Aerosol Complex Refractive Indices from AERONET Inversion Products over China

Contact Info

Product

Resources

About