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 enhanced aerosol concentrations acting as cloud condensation nuclei (CCN) and giant CCN (GCCN) as well as the effects of low-level moisture on tornadogenesis. An ensemble of four simulations were performed. In two of the simulations, initial background CCN and GCCN profiles were set to represent a relatively “clean” continental environment. In the other simulations, initial background aerosol profiles were set to represent an aerosol-polluted environment due to the presence of dust. For each pair of simulations where background aerosol concentrations were set up the same, the background low-level water vapor mixing ratio profile was adjusted by 20% among the simulations, thereby altering the ambient relative humidity profile at low levels. Results from these simulations will be presented, emphasizing differences in storm microphysics, resulting cold pool characteristics, and low-level storm dynamics. Furthermore, we will discuss which environment was most favorable for tornadogenesis.