Comparing aerosol and low-level moisture influences on supercell tornadogenesis: idealized simulations

Three-dimensional numerical simulations of an idealized supercell thunderstorm were conducted to assess the effects of low-level moisture and cloud condensation nuclei (CCN) on tornadogenesis. An ensemble of four simulations were performed using the Regional Atmospheric Modeling System (RAMS) in a nested grid setup. The initial background CCN profiles were set to represent a relatively “clean” continental environment in two of the simulations and an aerosol-polluted environment in the other simulations. The background low-level water vapor mixing ratio profile was adjusted by 20% among each pair of simulations where background aerosol concentrations were initialized the same, thereby altering the ambient relative humidity profile at low levels. Results from these simulations are presented, emphasizing differences in storm microphysics, resulting cold-pool characteristics, and low-level storm dynamics. Furthermore, we discuss which environment was most favorable for tornadogenesis.