A Monte Carlo Model for Soil Particle Resuspension Including Saltation and Turbulent Fluctuations

Figures & data

FIG. 1 Schematic of Monte Carlo simulation.

TABLE 1 Emission rates (kg m^–2s⁻¹) within the saltation layer except where noted. These data correspond to soils with different and, in some cases unknown, size distributions

	u∗(m/s)	1.0	0.85	0.75	0.60	0.50	0.25	0.10
	Los Angeles County	6.83 × 10^−3	1.22 × 10^−6	3.09 × 10^−9	8.42 × 10^−10	3.21 × 10^−10	6.40 × 10^−12	1.87 × 10^−14
	Allegheny County	2.53 × 10^−5	3.61 × 10^−6	1.16 × 10^−8	2.07 × 10^−9	1.08 × 10^−9	1.80 × 10 ^−11	2.14 × 10^−14
Huan et al. 2006	Wind tunnel		0.8	0.4	0.12
Shao and Mikami 2005	Takla Makan desert					∼0.001		0 to 0.01
Shao et al. 2003	Gobi desert (at rooftop height)	∼5 × 10^−6	∼3 × 10^−6	∼1 × 10^−6	∼1 × 10^−7	∼5 × 10^−8
Chen and Fryrear 2002	Big Spring, TX (at 0.25 m)	1.5 × 10^−2
Westphal et al. 1987	Model (PM 10 only)	∼1 × 10^−5	10^−7 to 8 × 10^−6	8 × 10^−7 to 10^−5	∼1 × 10^−6	3 × 10^−8 to 10^−6	2 × 10^−8 to 10^−7
Anderson and Hallet 1986	Model					0.05
Anderson and Hallet 1986	Bagnold model					0.07
Anderson and Hallet 1986	White model					0.11 to 0.13
Chepil and Woodruff 1957	Syracuse, KS (at 6 ft.)	1.03 × 10^−3	1.50 × 10^−4	5.51 × 10^−5		5.16 × 10^−6

FIG. 2 Mass flux rates within the saltation layer plotted against u∗³. Conditions were modeled to match Los Angeles and Allegheny County soil shown by diamonds and squares, respectively. For comparison purposes, flux estimates are shown from the models of Marticorena and Bergametti (1995) and Ginoux et al. (2001). The fraction of soil available for resuspension was assumed to be 0.2 in both cases. The Ginoux et al. lines are virtually identical for the two case studies illustrated.

TABLE 2 Simulated emission rates for particles within the saltation layer over a range of friction velocities. Units are m⁻²s⁻¹

u∗(ms^−1)	LA County	Allegh. County
0.10	5.22 × 10^5	3.40 × 10^5
0.25	3.61 × 10^7	4.71 × 10^7
0.50	6.20 × 10^8	1.08 × 10^9
0.60	1.29 × 10^9	1.89 × 10^9
0.75	3.19 × 10^9	5.98 × 10^9
0.85	4.90 × 10^9	7.36 × 10^9
1.0	9.21 × 10^9	1.71 × 10^10

FIG. 3 Mass concentrations of suspended and saltating particles with friction velocities of 0.85 m s⁻¹ and 1.0 m s⁻¹. The simulation time was 3 seconds in all cases.

FIG. 4 The mass concentration of particles in full suspension for friction velocities of 0.50, 0.75, and 1.0 m s⁻¹. Soil is characteristic of Los Angeles County. Particles in saltation are not shown.

FIG. 5 The mass concentration of particles in full suspension for friction velocities of 0.50, 0.75, and 1.0 m s⁻¹. Soil is characteristic of Allegheny County. Particles in saltation are not shown.

FIG. 6 The number concentration of suspended and saltating particles entrained in flows with u∗ = 0.85 m s⁻¹ and 1.0 m s⁻¹. The simulation time was 3 seconds in all cases.

FIG. 7 The number concentration of particles in full suspension for u∗ = 0.50, 0.75, and 1.0 m s⁻¹. Soil is characteristic of Los Angeles County. Particles in saltation are not shown.

FIG. 8 The number concentration of particles in full suspension for u∗ = 0.50, 0.75, and 1.0 m s⁻¹. Soil is characteristic of Allegheny County. Particles in saltation are not shown.

FIG. 9 The mean diameter calculated by both particle mass and particle number for Los Angeles and Allegheny Counties. Friction velocity is 0.75 m s⁻¹.

TABLE 3 Regression coefficients and R ² values for Equation (9)

	a	b	c	d	R ^2
LA by mass	−568	340	−37.4	2.923	0.966
LA by number	−340	280	−43.7	1.698	0.890
Allegh. by mass	−554	367	−44.5	3.407	0.980
Allegh. by number	−87.3	179	−33.9	1.515	0.917

FIG. 10 Aerodynamic entrainment probabilities for a range of particle diameters and u∗ = 0.50, 0.75, and 1.0 m s⁻¹.

FIG. 11 The mean horizontal wind profile with height during steady–state saltation is shown by the dotted line. A standard logarithmic profile is shown as a solid line for comparison. This is for u∗ = 0.75 m s⁻¹, z _o = 10⁻³ m, and a number flux of 3 × 10⁻⁹ m⁻² s⁻¹.

Marticorena , B. and Bergametti , G. 1995 . Modeling the Atmospheric Dust cycle: 1. Design of a Soil-Derived Dust Emission Scheme . J. Geophys. Res. , 100 ( D8 ) : 16 415 – 16 . 430

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Ginoux , P. , Chin , M. , Tegen , I. , Prospero , J. M. , Holben , B. , Dubovik , O. and Lin , S.-J . 2001 . Sources and Distributions of Dust Aerosols Simulated with the GOCART Model . J. Geophys. Res. , 106 : 20255 – 20273 .

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