A Method for Diagnosing the Sources of Infrasound in Convective Storm Simulations

Abstract

his paper presents a convenient method for diagnosing the sources of infrasound in a numerical simulation of a convective storm. The method is based on an exact acoustic wave equation for the perturbation Exner function ??. One notable source term (Suu) in the ?? equation is commonly associated with adiabatic vortex fluctuations, whereas another (Sm) is directly connected to the heat and mass generated or removed during phase transitions of moisture. Scale estimates suggest that other potential sources are usually unimportant. Simple numerical simulations of a disturbed vortex and evaporating cloud droplets are carried out to illustrate the infrasound of Suu and Sm. Moreover, the diagnostic method is applied to a towering cumulonimbus simulation that incorporates multiple categories of ice, liquid, and mixed-phase hydrometeors. The sensitivity of Sm to the modeling of the hail-to-rain category conversion is briefly addressed.