Abstract. Mineral dust aerosols (MDs) not only influence the climate by scattering and
absorbing solar radiation but also modify cloud properties and change the
ecosystem. From 3 April to 16 May 2014, a ground-based mobile laboratory was
deployed to measure the optical and microphysical properties of MDs near
dust source regions in Wuwei, Zhangye, and Dunhuang (in chronological order)
along the Hexi Corridor over northwestern China. Throughout this dust
campaign, the hourly averaged (±standard deviation) aerosol
scattering coefficients (σsp, 550 nm) of the
particulates with aerodynamic diameters less than 2.5 µm (PM2.5)
at these three sites were sequentially 101.5 ± 36.8,
182.2 ± 433.1, and 54.0 ± 32.0 Mm−1.
Correspondingly, the absorption coefficients (σap, 637 nm) were 9.7 ± 6.1, 6.0 ± 4.6, and 2.3 ± 0.9 Mm−1; single-scattering
albedos (ω, 637 nm) were 0.902 ± 0.025,
0.931 ± 0.037, and 0.949 ± 0.020; and
scattering Ångström exponents (Åsp,
450–700 nm) of PM2.5 were 1.28 ± 0.27,
0.77 ± 0.51, and 0.52 ± 0.31. During a
severe dust storm in Zhangye (i.e., from 23 to 25 April), the highest values
of σsp2.5 (∼ 5074 Mm−1), backscattering coefficient (σbsp2.5, ∼ 522 Mm−1), and ω637 (∼ 0.993) and the lowest values of
backscattering fraction (b2.5, ∼ 0.101) at 550 nm and Åsp2.5
(∼ −0.046) at 450–700 nm, with peak values of aerosol number size distribution
(appearing at the particle diameter range of 1–3 µm), exhibited that
the atmospheric aerosols were dominated by coarse-mode dust aerosols. It is
hypothesized that the relatively higher values of mass scattering efficiency during floating dust
episodes in Wuwei and Zhangye are attributed to the anthropogenic soil dust
produced by agricultural cultivations.
The Earth Surface Mineral Dust Source Investigation: An Earth Science Imaging Spectroscopy Mission
