Utilization of the depolarization ratio derived by AERONET Sun/sky radiometer data for type confirmation of a mixed aerosol plume over East Asia

This article confirms the utilization of depolarization ratio
derived by ground-based Aerosol Robotic Network (AERONET)
Sun/sky radiometer data obtained during a high-PM10 episode
at Gwangju, Korea (35.10° N, 126.53° E) in April 2009, in order to
determine the nature and source of the atmospheric aerosol
associated with this event. Integrated monitoring using satellite
and depolarization light detection and ranging (lidar) data,
together with model analysis, was also completed for the period
of the high-PM10 event. The Sun/sky radiometer-derived particle
depolarization ratio values are similar to the lidar-derived
values, and these values highlight the effect of dust particles
on aerosol observation. High particle depolarization ratios (12.5–
14.2%) were observed when the aerosol plume transported
from the west between 5 and 7 April. In contrast, lower particle
depolarization ratios (5.8–9.8%) were detected when the aerosol
plume was transported from the north on other observation
days. Different optical properties are also shown according to
the variation of depolarization ratio. High values in the real part
of the refractive index (1.47–1.49 at 440 nm), lower values in the
imaginary part of the refractive index (0.007–0.009 at 440 nm),
and a high proportion of coarser particles were observed during
the high depolarization ratio period. In contrast, the atmospheric
aerosol transported from the north showed characteristics
more commonly associated with smoke, with lower values
in the real part of the refractive index (1.41–1.48 at 440 nm),
higher values in the imaginary part of the refractive index
(0.008–0.011), and a high proportion of fine particles. This indicates
that the Sun/sky radiometer-derived depolarization ratio is
a useful parameter when estimating the effect of dust particles
during high-PM10 events.