Observations of Infrasound and Subsonic Disturbances Related to Severe Weather

Summary During the past 10 years the Geoacoustics Group of NOAA's Wave Propagation Laboratory studied travelling low-frequency pressure variations related to thunderstorms and severe weather. Two general categories of waves were associated with severe weather conditions: 'subsonic' pressure disturbances and infrasonic waves with acoustic velocities. The low-frequency pressure variations were measured at the Earth's surface using microphone arrays located at times thousands of kilometres from the severe-weather disturbance. The radiated infra- sound was related to thunderstorms penetrating the tropopause and spectral analyses were performed on several signals. Possible practical applications to storm warning and classification are discussed for both infrasound and 'subsonic' pressure disturbances. Past measurements of these signals are reviewed.