Synergetic analysis of springtime air pollution episodes over Gwangju, Korea

The characteristics of springtime aerosols, including their optical and microphysical properties, were analyzed for the months of March to May of 2009 in Gwangju (35.23°N, 126.84°E), Korea. A high Light Detection and Ranging (LIDAR)-derived aerosol depolarization ratio (δ) of 0.25±0.04 was determined on dust particles during the observation period. The Ångström exponent values of the 440-870nm wavelength pair (Å_440-870) and single-scattering albedo at 675nm (Ω₆₇₅) measured by a CIMEL sun/sky radiometer were 0.77±0.19 and 0.95±0.01, respectively. The elevated dust layers reached a maximum elevation of 4km above sea level. Anthropogenic/smoke particles that originated from highly populated/industrialized regions could be distinguished by their relatively smaller particle size (Å_440-870 ranged between 1.33 and 1.36) and higher light-absorbing (Ω₆₇₅ of 0.92±0.01) characteristics. These aerosols are mostly distributed at altitudes <1.2km. The root-mean-square deviation (RMSD) between the aerosol optical depth (AOD, τ) derived from LIDAR (τ_LIDAR) and from the CIMEL sun/sky radiometer (τ_CIMEL) varied with respect to the surface PM₁₀ concentration. The RMSD between τ_LIDAR and τ_CIMEL was as low as 13% under lower PM₁₀ concentration levels (<100μg/m³). In contrast, the RMSD between τ_LIDAR and τ_CIMEL increased three times (~31%) under high surface PM₁₀ concentration levels (>100μg/m³). These results suggest that the accuracy of τ_LIDAR is influenced by specific atmospheric conditions, regardless of its uncertainty.