Inversion of infrasound signals for passive atmospheric remote sensing

Abstract

During the past few years, significant progress has been made in our understanding of atmospheric propagation of infrasound signals from both natural and man-made impulsive events. In this chapter, we review this progress within the framework of the early history of infrasound remote sensing, including basic geophysical remote sensing theory and linear acoustic wave propagation. Also, we review the capabilities and limitations of current global atmospheric specification models used in propagation studies. We believe that the state-of-the-art in infrasound propagation research has advanced sufficiently, so that the opportunity is now at hand to turn the problem around and use detections of infrasound to improve our knowledge of upper atmospheric winds and temperatures, which are the main affecting quantities. Accordingly, we employ an approach called discrete inverse theory, a concept developed by the seismographic and oceanographic communities, to retrieve winds and temperatures by inverting infrasound observations. We demonstrate the methodology through application to an extensive time series of synthetic data that were generated using an atmospheric model as the truth. The results of several illustrative numerical experiments carried out with an existing infrasound network show that with selected assumptions, infrasound signals from a single impulsive event can be inverted to provide quantitative information on the state of the middle-and upper atmosphere. We conclude that this approach to infrasound signal inversion is an important step forward in atmospheric remote sensing and we propose several ideas for future directions. © 2009 Springer Science+Business Media B.V.