Depolarization Ratios Retrieved by AERONET Sun/Sky Radiometer Data and Comparison to Depolarization Ratios Measured With Lidar

Youngmin Noh^{1}, Detlef Müller^{2}, Kyunghwa Lee^{3}, Kwanchul Kim^{3}, and Kwonho Lee^{4}^{1}International Environmental Research Center, Gwangju Institute of Science and Technology (GIST), Korea ^{2}University of Hertfordshire, United Kingdom ^{3}Gwangju Institute of Science and Technology (GIST), Korea ^{4}Gangneung-Wonju National University, Korea

Received: 29 Dec 2016 – Accepted for review: 11 Feb 2017 – Discussion started: 17 Feb 2017

Abstract. The linear particle depolarization ratios at 440, 675, 870, and 1020 nm were derived using data taken with 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 R^{2} between the linear particle depolarization ratio derived by AERONET data at 1020 nm and the linear particle depolarization ratio measured with lidar at 532 nm is 0.90, 0.92, 0.79, and 0.89 at Seoul, Kongju, Gosan, and Osaka, respectively. A good correlation between the lidar-measured depolarization ratio at 532 nm and the one retrieved by AERONET at 870 nm. We find correlation coefficients R^{2} of 0.89, 0.92, 0.76, and 0.88 at Seoul, Kongju, Gosan, and Osaka, respectively. The correlation coefficient for the data at 675 nm is lower than the correlation coefficient at 870 and 1020 nm. We find correlation values of 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. We find values of 0.38, 0.62, 0.26, and 0.28 at Seoul, Kongju, Gosan, and Osaka, respectively. 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 mixed with anthropogenic pollution particles. The single-scattering albedo decreases with increasing measurement wavelength for low linear particle depolarization ratios. In contrast, single-scattering albedo increases with decreasing wavelength for high linear particle depolarization ratios. The retrieved volume particle size distributions are dominated by the fine-mode fraction if linear particle depolarization ratios are less than 0.15 at 532 nm. The fine-mode fraction of the size distributions decreases and the coarse-mode fraction of the size distribution increases for increasing the linear particle depolarization ratio at 1020 nm. The dust ratio based on using the linear particle depolarization ratio derived from AERONET data is 0.12 to 0.17 lower than the coarse-mode fraction derived from the volume concentrations of particle size distributions in which case we can compute the coarse-mode fractions of dust.

Citation:
Noh, Y., Müller, D., Lee, K., Kim, K., and Lee, K.: Depolarization Ratios Retrieved by AERONET Sun/Sky Radiometer Data and Comparison to Depolarization Ratios Measured With Lidar, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1181, in review, 2017.

Youngmin Noh et al.

Youngmin Noh et al.

Youngmin Noh et al.

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