Abstract
Microbaroms are a class of atmospheric infrasound that is characterized by narrow-band, nearly sinusoidal waveforms with periods near 5 s. These waves are generated by marine storms and are observed at infrasound sites across the globe. We report here on a study of microbarom wave packets. The data analyzed were obtained using the University of Alaska infrasound array comprised of 4 microphones located in central Alaska. Exploiting the narrow-band feature of the microbarom signals we are able to apply the Hilbert transform as a method for finding phase breaks in the signal. The phase breaks are interpreted to be the demarcations of the boundaries of individual wave packets. When applied to long sequences of microbaroms we find a broad distribution of packet lengths that diminishes monotonically with length, with a mean near 10 cycles and a variance nearly as large. Once the packets are identified, high-resolution estimators have been used to obtain the distribution of arrival directions at the array site. The ensemble of arrival directions is a reflection of the possibility of multiple sources and/or multiple propagation paths between the sources and the array.
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