Infrasound from tornadoes

Tornadoes are known to radiate infrasound. The physical mechanism underlying the infrasonic radiation generated by tornadoes is not well understood. In this work, we use Lighthill's acoustic analogy and the theory of vortex sound to predict the pressure signals emitted from numerically simulated tornadoes which are produced in an LES model by researchers from the Penn State Department of Meteorology. The interesting patterns of the acoustic pressure in a low-frequency band strongly imply a rotating quadrupole source inside the tornado. A column of Kirchhoff vortices is the best potential candidate as a tornado-like source based on the analytical work. By applying acoustic propagation models in a stratified atmosphere, we want to find evidence of the predicted infrasonic signals in the signals detected in data collected during field experiments.