Size distribution and element composition of dust aerosol in Chinese Otindag Sandland

The particle size distribution function is one of the characteristics reflecting the composition of aerosol during sand lifting and removal in desert regions. This characteristic, in addition to known practical applications, is important in describing radiation processes during the exchange of heat fluxes and in forming cloud systems in the models of atmospheric dynamics. Fine dust-aerosol fractions (less than 2 &#181;m in diameter) are especially important for the atmospheric radiation budget, because such fractions (having a significant lifetime) most efficiently interact with short-wave solar radiation. One of the central regularities in considering the size distributions of simulated dust-aerosol particles is the following formula based on the so-called fragmentation process and verified using a large amount of empirical data N (d) ~ d -2. Similar dependence for particles with size d > 1 &#181;m is associated with the consideration of the fragmentation process as a particle splitting according to the log-normal distribution.Results of field measurements taken in the near&#8211;Caspian (2002, 2003, 2007, 2009, 2010, 2011, 2013, 2014, 2016 years) and near&#8211;Aral-sea (1998) deserts under the conditions of weak winds (almost in the absence of saltation processes) and strong heating of the land surface are given. These results show that the fine mineral dust aerosol (0.1-1 &#181;m) considerably contributes to the total aerosol content of the atmospheric surface layer under such conditions. The scaling of daytime mean size d distribution at a height of 2 m is close to d -5&#160;in contrast to the law d -2 for fraction&#160;d >1 &#181;m.Different compositions of aerosol particles at 0.1 < d < 1 &#181;m, and d >1 &#181;m, including multicomponent fractions (less than 1 &#181;m) may result in different probabilities of their integration and disintegration, which, finally, determine equilibrium particle size distributions. The simplest distribution approximations based on the Kolmogorov direct differential equation are given.&#160;This study was supported by the RFBR (19-05-50110) and the Presidium of the Russian Academy of Sciences (programs 12 and 20).

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Roles of saltation, sandblasting, and wind speed variability on mineral dust aerosol size distribution during the Puerto Rican Dust Experiment (PRIDE)

Journal of Geophysical Research Atmospheres ◽

10.1029/2003jd004233 ◽

2004 ◽

Vol 109 (D7) ◽

Cited By ~ 66

Author(s):

Alf Grini

Keyword(s):

Wind Speed ◽

Puerto Rican ◽

Size Distribution ◽

Mineral Dust ◽

Dust Aerosol ◽

Aerosol Size Distribution

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Analysis of the vertical structure and size distribution of dust aerosols over the semi-arid region of the Loess Plateau in China

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-6113-2012 ◽

2012 ◽

Vol 12 (2) ◽

pp. 6113-6143 ◽

Cited By ~ 3

Author(s):

B. Zhou ◽

L. Zhang ◽

X. Cao ◽

X. Li ◽

J. Huang ◽

...

Keyword(s):

Size Distribution ◽

Dust Aerosol ◽

Scattering Coefficient ◽

The Loess Plateau ◽

Dust Aerosols ◽

Depolarisation Ratio ◽

Aerosol Scattering ◽

Semi Arid Region ◽

Aerosol Extinction Coefficient ◽

Semi Arid

Abstract. Using measurements of dual-wavelength polarisation lidar, particle sizer, and nephelometer from the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL), the properties of dust aerosol extinction coefficient, optical depth, depolarisation ratio, colour ratio, size distribution, and concentration over the semi-arid region of the Loess Plateau in north-western China are analysed in a case study of dust storms from 16–18 March 2010. The results show that dust aerosols are distributed mostly within the lower layer (below 3.0 km), with the dust aerosol extinction coefficient ranging from 0.1 to 1.0 km−1. The average optical depth and depolarisation ratio are near 0.6 and 0.3, respectively, while the colour ratio ranges from 0.8 to 1.0. The mass size distribution of dust aerosols has two peaks at 0.7 μm and 5.0 μm, respectively, while the number size distribution of dust aerosols is log-normal with a maximum near 0.8 μm. Particles in the fine mode (r ≤ 2.5 μm) are predominant in the dust storm. Their number concentration decreases while those of particles in the moderate (2.5 μm < r ≤ 10.0 μm) and coarse (10.0 μm < r ≤ 20.0 μm) modes increase. Based on Mie theory and the number size distribution of the aerosol, the dust aerosol scattering coefficient and its variation with particle size are calculated and analysed. A fairly close correlation is found with that measured by the nephelometer, for which the correlation coefficients are 0.89 and 0.94, respectively, at 520 and 700 nm. It shows a Gaussian distribution of dust aerosol scattering coefficient against effective diameter, with a fitting coefficient of 0.96 and centre diameter of 5.5 μm. The contribution percentages of aerosol within fine, moderate, and coarse modes to dust aerosol scattering coefficient are 20.95%, 62.93%, and 16.12%, respectively, meaning that PM10 is a dominant factor in the dust aerosol scattering properties.

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