Sensitivity Studies on the Impact of Dust and Aerosol Pollution Acting as Cloud Nucleating Aerosol on Orographic Precipitation in the Colorado River Basin

Table 1

RAMS model configuration.

Model aspect	Setting
Grid	Arakawa C grid [1]
	Three grids
	Horizontal grid:
	grid 1:  km; 150 × 64 points
	grid 2:  km; 122 × 101 points
	grid 3:  km; 210 × 170 points
	Vertical grid: variable (75 m at the surface; maximum of 800 m)
	35 vertical levels
	Model top: ~20 km
	10 levels below 1 km
Initialization	1° GFS data; Soil data initialized with ~32 km NARR analyses [12]
Time step	30 s
Simulation duration	10 days for each case study
Microphysics scheme	Two-moment bin-emulating microphysics [13–15]; Water species: vapor, cloud1 and cloud2 cloud drops, rain, pristine ice, snow, aggregates, graupel, and hail; DeMott et al. [16] heterogeneous ice nucleation and new lookup table including adsorption theory for dust [17]
Aerosol and dust sources	GEOS-Chem and RAMS regional dust sources; dust sources also present in the nonanthropogenic control run
Boundary conditions	Radiative lateral boundary [18]; Top: rigid lid with a high-viscosity layer aloft to damp gravity waves, by nudging to large-scale analysis or initial conditions [1]
Turbulence scheme	Mellor and Yamada [19]; level 2.5 scheme on grids 1–3; Smagorinsky [20]; the Kain and Fritsch [21] cumulus parameterization applied to grids 1 and 2; convection was resolved explicitly on grid 3
Radiation scheme	Harrington [22], with additions from Stokowski [23]
Surface scheme	LEAF-3 [24]