Infrasound Radiation from Severe Storms Free

A review of experimental evidence over the last two decades leads to the conclusion that 1 to 100 MW of low‐frequency acoustic energy is radiated from the immediate neighborhood of many severe meteorological storms. The most convincing evidence is from simultaneous observations of space‐time correlated pressure fluctuations on widely separated microphone arrays in the United States, together with National Weather Service meteorological data on the occurrence of midcontinent storms. Presence of sound in the ionosphere above some of the same storms has been inferred from Doppler phase fluctuations where the ionospheric reflection points are located above the storm area. A broad frequency spectrum with periods from a few seconds to a few minutes has been found, and asymmetric propagation is probably due to stratospheric winds. Direction and directional changes of sound from nearby thunderstors, together with weather radar results, indicate that funnels, tornados, and hail need not be present but that the radiation occurs from very high clouds that often penetrate the tropopause. The radiating mechanism from these storm systems is not yet completely understood.