Dust Lofting and Ingestion by Supercell Storms

Abstract

ecent research pertaining to aerosol impacts on cloud microphysics has shown a need for understanding mineral dust entrainment into moist convection. The goal of this study is to examine the pathways in which nonmicrophysically active mineral dust is entrained into supercell storms within three commonly observed dust regimes. The Regional Atmospheric Modeling System (RAMS) with an interactive dust model that allows for surface emission was used to achieve this goal.First, a supercell is simulated within an already dusty environment (EXP-BACKGROUND) to investigate ingestion purely from a background source. Second, the supercell is simulated within a clean background environment and lofts its own dust via the interactive dust model (EXP-STORM) to investigate the regime in which the only source of dust in the atmosphere is due to the storm itself. Finally, the supercell is simulated with a low-level convergence boundary introduced ahead of the supercell to investigate dust lofting by outflow boundary interactions (EXP-BOUNDARY). Results indicate that the supercell in EXP-BACKGROUND ingests large dust concentrations ahead of the rear flank downdraft (RFD) cold pool. Conversely, dust lofted by the cold pool in EXP-STORM is ingested by the supercell in relatively small amounts via a narrow corridor generated by turbulent mixing of the RFD cold pool and ambient air. The addition of a convergence boundary in EXP-BOUNDARY is found to act as an additional source of dust for the supercell. Results demonstrate the importance of an appropriate dust representation for numerical modeling.