Abstract. The POLIPHON (polarization lidar photometer networking)
method is a powerful pathway to retrieve the height profiles of dust-related
particle mass and ice-nucleating particle (INP) concentrations. The
conversion factors fitted from the sun photometer observation data are the
major part of the POLIPHON computations, which can convert the
polarization-lidar-derived dust extinction coefficients into
dust-related particle mass and INP concentrations. For the central Chinese
megacity of Wuhan (30.5∘ N, 114.4∘ E), located at the
downstream area several thousands of kilometers far away from the source
regions of Asian dust, dust particles always mix with other aerosols from
local emissions. Therefore, very few dust case data sets can be available
when using the column-integrated Ångström exponent (for 440–870 nm) <0.3 and aerosol optical depth (at 532 nm) >0.1
recorded by a sun photometer as the filtering criteria. Instead, we present
another dust case data set screening scheme that applies the simultaneous
polarization lidar observation to verify the occurrence of dust. Based on
the 33 dust-intrusion days identified during 2011–2013, the
extinction-to-volume (cv,d) and extinction-to-large particle
(with radius >250 nm) number concentration
(c250,d) conversion factors are determined to be
(0.52±0.12)×10-12Mmm3m-3
and 0.19±0.05 Mm cm−3, respectively. The c250,d
for Wuhan is 27 % larger than that observed at Lanzhou SACOL
(36.0∘ N, 104.1∘ E), a site closer to the Gobi Desert,
and tends to be closer to those observed in North Africa and the Middle East,
indicating dust aerosols from these two sources are also possibly involved
in the dust events observed over Wuhan. As a comparison, the conversion
factor c290,c of 0.11±0.02Mmcm-3 for continental aerosol is much smaller than
c250,d, indicating that there is no significant influence of
urban aerosols on the retrievals of dust-related conversion factor over
Wuhan. The conversion factors are applied in a dust event in Wuhan to reveal
the typical dust-related immersion-mode INP concentration over East Asian
cities. The proposed dust case data set screening scheme may potentially be
extended to the other polluted city sites that are more influenced by mixed dust.
Dust Model Intercomparison Between ADAM and CFORS/Dust For Asian Dust Case in 2007 (March 28 - April 3)
