On the sensitivity of infrasound to the upper atmosphere.

Abstract

In comparison to the lower atmosphere where comprehensive global atmospheric specifications are commonplace, measuring the properties of the atmosphere above the stratosphere is an active area of scientific research. Here, we revisit the use of infrasound as a remote sensing technique for the upper atmosphere. Infrasonic signals from the Tungurahua volcano in Ecuador are used to investigate the behavior of the upper atmosphere. Depending on the atmospheric conditions, stratospheric, mesospheric, and thermospheric arrivals are observed during intervals of explosive volcanic activity. It is found that the travel times of the thermospheric arrivals exhibit a coherent variability with periods equal to those of the harmonics of the atmospheric tides. Theoretical predictions using atmospheric specifications show that the stratospheric arrivals are well predicted but that significant discrepancies exist for arrivals from higher altitudes. As such, these observations suggest a readily accessible means of passive ...