| Sand aerosol concentrations and particle size distribution have been measured by APS-3310A (made by U.S.A) in Bayinhaote, Yanchi and Ymchuan. A lot of data have been collected under different weather conditions, i.e. background, dust, sand-blowing, sand storm. The rules of sand aerosol concentrations' and instantaneous particle size distributions' variation are found through statistical analysis. The sand aerosol particle size distributions have been fitted by the method of non-linear least squares, and its errors are analyzed.First, sand aerosol concentrations' variations are analyzed in different weather.Sand aerosol concentrations are changeable in different weather process. Sandaerosol concentrations (number concentrations, surface concentrations, massconcentrations) increase in turn in background atmosphere, dust, sand blowing, sandstorm weather. Background atmospheric sand aerosol concentrations (numberconcentrations, surface concentrations and mass concentrations) are 25~29grains/cm~3,223~255μm~2/cm~3, 0.32~0.4mg/m~3;In dust weather, they are 28~45grains/cm~3,249~412μm~2/cm~3, 0.25~0.43mg/m~3;In sand-blowing weather, they are56~156grains/cm~3, 405~1419μm~2/cm~3 and 0.43-1.89mg/m~3;And the aerosolconcentrations in sand storm are 209~359grains/cm~3, 1337~2533μm~2/cm~3,1.42~2.95mg/m~3 in turn. The number concentrations of dust focus on 0.1-1.0μm.That of sand-blowing has the same distribution between 0.1~1.0μm and 1.0~2.0μm.The number concentrations of sand storm accumulate in the diameter less than2.0μm, and the distribution in 1.0~2.0μm is larger than that in 0.1~1.0μm. In fourweather, 90% of mass concentrations accumulate in l.0μm -10.0μm. The weight ofsurface concentrations in less than 2.0μm and great than 2.0μm to total surfaceconcentrations are 0.45 and 0.55. And that of mass concentrations in the diameters are 0.30 and 0.70 or so.Second, the transmutation of sand aerosol particle size distributions(size-number distributions, size-surface distributions and size-mass distributions) areanalyzed. During all weather, all concentration spectrums display a unimodal form,and different spectrums are different. Instantaneous concentration spectrums changea little, and the peak concentrations vary appreciably, changing with concentrationsfor identical sand weather. Three sand particle size distributions (size-numberdistributions, size-surface distributions, size-mass distributions) are narrow in dust.During the weather., corresponding peak diameters are in 1.036-1.286um,2.128~2.287um and 2.287~3.050um separately. In the end, the peak diameters' rangedecreased. The spectrums in sand-blowing are broad. The peak concentrations ofsize-number distributions increase from 5grains/cm3 to 8 grains/cm3 in the first halfan hour, and then its decrease to the end, and reach 3 grains/cm3. The peak diameterschiefly vary in 0.835-0.897(im and 0.897~0.964um. To size-surface distributions,peak diameters vary from 36 to 56um2/cm3, and then to 18um2/cm3. The initial peakdiameters are in 2.287~3.050um, and that of intermediate stage is 2.128~2.838um.In terminal phase it is 2.128~2.458um. The peak diameters of size-mass distributionsare in 2.458-5.892um. When the sand storm begins, its peak concentrations reach 23grains/cm , and decrease to 14 grains/cm3 after keeping such value some time. Thepeak diameters change in 0.728~0.835um. And the size-surface and size-massdistributions' peak concentrations have the same variations. The peak diameters ofsize-surface distributions enlarge from 2.287~2.458um to 2.128~2.838um. The peakdiameters of size-mass distributions are in 2.838~4.697um.Three, the sand aerosol particle size distributions have been fitted and its errors are analyzed. In dust weather, the simulated parameters of size-number distributions,size-mass distributions and size-surface distributions are 1.114-1.158um, 1.50-1.53and 3.3~5.3grains/cm3, 1.611-1.689um, 1.60-1.63 and 20.4~32.8um2/cm3,2.011~2.121nm, 1.53-1.62 and 0.016~0.027mg/m3. In sand-blowing weather, thecorresponding simulated parameters are 0.565-0.763 (j.m, 1.75~2.03and10.3~25.5grains/cm3, 1.134~1.675um, 1.83-2.20 and 35.9~95.3um2/cm3,2.249-2.641 nm, 1.73-1.88 and 0.027-0.082 mg/m3. And in the sand storm, they are0.498~0.686um, 1.66-2.0 and 55.3-80.3grains/cm3,1.150~1.56um,1.88~2.12and121~199^m2/cm3, 2.192-2.519um, 1.71-1.84 and 0.078-0.143 mg/m3. Thesimulated peak diameters in sand-blowing and sand storm change a little, and theconstant C has great change. In sandblowing and storm weather, the standarddeviation of size-surface distribution is nearby 2, and that of size-number andsize-mass distributions are changing in 1.6-2.0. And that of dust is between 1.5 and1.7. The fitting constants can reflect transmutation character of sand weather process.The instantaneous measured size distributions of sand aerosol can be fitted verywell by one log-normal distribution function whose fitting result is well than Dmodel function and Junge model function's segmentation simulation. The relativeerror of D model and Junge model function is larger than log-normal distributionfunction's by 0.1-0.6 times. The simulate result of D model function and Jungemodel function can't get good effect in the same diameters' range at the same time.
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