NEWS | May 11, 2010

NRL Contributes to Book on Infrasound

By Donna McKinney

Naval Research Laboratory physicist Douglas Drob, in the Upper Atmospheric Physics Branch of the Space Science Division (SSD) together with co-authors R.R. Meier and J.M. Picone of George Mason University and M. Garcés of the University of Hawaii has published a chapter Inversion of Infrasound Signals for Passive Atmospheric Remote Sensing in the monograph Infrasound Monitoring for Atmospheric Studies. The book, written by the world's leading experts in infrasound, is a compilation of the current research in this broad interdisciplinary field. Drob is also a contributor to several other chapters in the book.

Because infrasound, sound waves below 20 Hz, can travel for thousands of kilometers, atmospheric conditions play an important role in the propagation characteristics. Infrasound monitoring is a standard technique for seismology, and recent NRL research has suggested it can be used for atmospheric remote sensing. Modeling studies have shown that there are clear seasonal and local time variations in infrasound propagation characteristics that are directly correlated with changes in atmospheric state.

Winds in the 35 to 150 km altitude region are notoriously difficult to measure directly; new techniques in this area would be a significant advance. Drob and his co-authors investigate the feasibility of acoustic infrasound tomography to obtain meaningful information with existing infrasound networks. They conclude that given suitable measurements of infrasound signals from impulsive infrasound events, passive infrasound remote sensing can indeed provide improved knowledge of the middle- and upper atmosphere; particularly in conjunction with other simultaneous atmospheric measurements. Other chapters of the book describe the NRL Ground to Space (G2S) semiempirical atmosphere model and its application to infrasound monitoring.