Sensitivity of Ensemble Simulations of Idealized Tropical Cyclones to Variations in Saharan Dust Concentrations

R.J. Maliawco¹, G.M. McFarquhar¹, B.F. Jewett¹

¹University of Illinois at Urbana-Champaign

Previous studies have hypothesized that the Saharan Air Layer (SAL) can impact tropical cyclones (TCs) through the action of embedded dust as cloud condensation nuclei (CCN). Here, a series of ensemble simulations where CCN are varied in the context of uncertainties in other model parameters are conducted with the Regional Atmospheric Modeling System (RAMS) version 6.0. The ensemble of simulations consist of small changes in temperature, relative humidity, trade wind inversion height and strength, mid-level easterly jet intensity and the strength and location of the warm bubble used to initialize convection. Different CCN profiles, where initial concentrations vary from 100, 101, 102, 500, 1000, 1500 and 2000 cm^-3 between 1 and 5 km, are input to each member of the ensemble. With a 2-km inner domain resolution, an initial vortex develops for 4 days. Comparing the ensemble members allows a determination of whether variations in the CCN concentration enhance, decrease, or have no effect on TC intensity, and whether sensitivities to perturbations in initial conditions mask aerosol indirect effects. The dependence of cloud and precipitation properties in both the spiral rainbands and eyewall convection on CCN concentration is also determined.