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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 17, issue 10 | Copyright
Atmos. Chem. Phys., 17, 6271-6290, 2017
https://doi.org/10.5194/acp-17-6271-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 22 May 2017

Research article | 22 May 2017

Depolarization ratios retrieved by AERONET sun–sky radiometer data and comparison to depolarization ratios measured with lidar

Youngmin Noh1, Detlef Müller2, Kyunghwa Lee3, Kwanchul Kim3, Kwonho Lee4, Atsushi Shimizu5, Itaru Sano6, and Chan Bong Park7 Youngmin Noh et al.
  • 1International Environmental Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea
  • 2School of Physics, Astronomy and Mathematics, University of Hertfordshire, Hertfordshire, UK
  • 3Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea
  • 4Department of Atmospheric and Environmental Sciences, Gangneung-Wonju National University, Gangneung, South Korea
  • 5National Institute for Environmental Studies, Tsukuba, Japan
  • 6Graduate School of Science and Engineering, Kindai University, Osaka, Japan
  • 7Department of Electronic Engineering, Mokwon University, Daejeon, South Korea

Abstract. The linear particle depolarization ratios at 440, 675, 870, and 1020nm were derived using data taken with the AERONET sun–sky radiometer at Seoul (37.45°N, 126.95°E), Kongju (36.47°N, 127.14°E), Gosan (33.29°N, 126.16°E), and Osaka (34.65°N, 135.59°E). The results are compared to the linear particle depolarization ratio measured by lidar at 532 nm. The correlation coefficient R2 between the linear particle depolarization ratio derived by AERONET data at 1020nm and the linear particle depolarization ratio measured with lidar at 532nm is 0.90, 0.92, 0.79, and 0.89 at Seoul, Kongju, Gosan, and Osaka, respectively. The correlation coefficients between the lidar-measured depolarization ratio at 532nm and that retrieved by AERONET at 870nm are 0.89, 0.92, 0.76, and 0.88 at Seoul, Kongju, Gosan, and Osaka, respectively. The correlation coefficients for the data taken at 675nm are lower than the correlation coefficients at 870 and 1020nm, respectively. Values are 0.81, 0.90, 0.64, and 0.81 at Seoul, Kongju, Gosan, and Osaka, respectively. The lowest correlation values are found for the AERONET-derived linear particle depolarization ratio at 440 nm, i.e., 0.38, 0.62, 0.26, and 0.28 at Seoul, Kongju, Gosan, and Osaka, respectively. We should expect a higher correlation between lidar-measured linear particle depolarization ratios at 532nm and the ones derived from AERONET at 675 and 440nm as the lidar wavelength is between the two AERONET wavelengths. We cannot currently explain why we find better correlation between lidar and AERONET linear particle depolarization ratios for the case that the AERONET wavelengths (675, 870, and 1020nm) are significantly larger than the lidar measurement wavelength (532nm).

The linear particle depolarization ratio can be used as a parameter to obtain insight into the variation of optical and microphysical properties of dust when it is mixed with anthropogenic pollution particles. The single-scattering albedo increases with increasing measurement wavelength for low linear particle depolarization ratios, which indicates a high share of fine-mode anthropogenic pollution. In contrast, single-scattering albedo increases with increasing wavelength for high linear particle depolarization ratios, which indicated a high share of coarse-mode mineral dust particles. The retrieved volume particle size distributions are dominated by the fine-mode fraction if linear particle depolarization ratios are less than 0.15 at 532nm. The fine-mode fraction of the size distributions decreases and the coarse-mode fraction of the size distribution increases for increasing linear particle depolarization ratio at 1020nm. The dust ratio based on using the linear particle depolarization ratio derived from AERONET data is 0.12 to 0.17. These values are lower than the coarse-mode fraction derived from the volume concentrations of particle size distributions, in which case we can compute the coarse-mode fraction of dust.

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Short summary
This paper compares the particle linear depolarization ratio retrieved by AERONET with respect to the one measured by lidar. We can confirm that AERONET derived linear particle depolarization ratio can be used to retrieve the dust ratio in mixed dust plumes. We expect that our results can increase availability of AERONET sun–sky radiometer data in the atmospheric aerosol research and aerosol type classification.
This paper compares the particle linear depolarization ratio retrieved by AERONET with respect...
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