Global morphology of infrasound propagation

Drob, D. P.; Picone, J. M.; Garcés, Milton

doi:10.1029/2002jd003307

Cited by 283 publications

(263 citation statements)

References 42 publications

(46 reference statements)

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“…However, such arrivals are typically characterized by small amplitudes, which is not in line with the observations. In an earlier study by Antier et al [2007], Ground-To-Space (G2S) [Drob et al, 2003] models have been validated using infrasound from Mount Yasur. The G2S specifications used by Antier et al [2007] were based on the NOAA Global Forecast System (GFS) operational analysis fields [Kalnay et al, 1990] in the 0 to 35 km altitude region, the NASA GEOS4 (Goddard Earth Observing System Version 4) system outputs [Bloom et al, 2005] in the 35 to 65 km region, and the HWM93/NRLMSISE-00 empirical models [Hedin et al, 1996;Picone et al, 2002] above.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of wind and temperature profiles from ECMWF analysis on two hemispheres using volcanic infrasound

et al. 2014

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In this paper, we evaluate vertical wind and temperature profiles that are produced by the European Centre for Medium‐Range Weather Forecasts (ECMWF) atmospheric analysis. The evaluation is carried out on both hemispheres: we make use of stratospheric infrasound arrivals from Mount Etna (37°N) and Mount Yasur (22°S). The near‐continuous, high activity of both volcanoes permits the study of stratospheric propagation along well‐defined paths with a time resolution ranging from hours to multiple years. Infrasound observables are compared to theoretical estimates obtained from acoustic propagation modeling using the ECMWF analysis. While a first‐order agreement is found for both hemispheres, we report on significant discrepancies around some of the equinox periods and other intervals during which the atmosphere is in a state of transition and dynamical oscillations of the atmosphere dominate over the general circulation. We present an inversion study in which we make use of measured trace velocity estimates to estimate first‐order effective sound speed model updates in a Bayesian framework. Deviations from the a priori models around the stratopause up to 10% (≈ 30 m s−1) are estimated. Such updates are in line with the results from comparisons between ECMWF analysis and observations from lidar and microwave Doppler spectroradiometer facilities that were colocated during the course of the 2012–2013 Atmospheric dynamics Research and InfraStructure in Europe (ARISE) measurement campaign.

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Section: Discussionmentioning

confidence: 99%

Evaluation of wind and temperature profiles from ECMWF analysis on two hemispheres using volcanic infrasound

et al. 2014

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“…[63] We performed ray tracing using the approach of Garcés et al [1998] using ground to space (G2S) semiempirical atmospheric specifications for the study region [Drob et al, 2003]. The G2S profiles have a horizontal resolution of $1°Â 1°, a vertical resolution of 200 m, and a temporal resolution of 6 h. They, therefore, lack the finer mesoscale structure required to fully resolve atmospheric propagation at this scale.…”

Section: Ray Tracingmentioning

confidence: 99%

The source of infrasound associated with long‐period events at Mount St. Helens

Matoza¹,

Garcés²,

Chouet³

et al. 2009

J. Geophys. Res.

101

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[1] During the early stages of the [2004][2005][2006][2007][2008] Mount St. Helens eruption, the source process that produced a sustained sequence of repetitive long-period (LP) seismic events also produced impulsive broadband infrasonic signals in the atmosphere. To assess whether the signals could be generated simply by seismic-acoustic coupling from the shallow LP events, we perform finite difference simulation of the seismo-acoustic wavefield using a single numerical scheme for the elastic ground and atmosphere. The effects of topography, velocity structure, wind, and source configuration are considered. The simulations show that a shallow source buried in a homogeneous elastic solid produces a complex wave train in the atmosphere consisting of P/SV and Rayleigh wave energy converted locally along the propagation path, and acoustic energy originating from the source epicenter. Although the horizontal acoustic velocity of the latter is consistent with our data, the modeled amplitude ratios of pressure to vertical seismic velocity are too low in comparison with observations, and the characteristic differences in seismic and acoustic waveforms and spectra cannot be reproduced from a common point source. The observations therefore require a more complex source process in which the infrasonic signals are a record of only the broadband pressure excitation mechanism of the seismic LP events. The observations and numerical results can be explained by a model involving the repeated rapid pressure loss from a hydrothermal crack by venting into a shallow layer of loosely consolidated, highly permeable material. Heating by magmatic activity causes pressure to rise, periodically reaching the pressure threshold for rupture of the ''valve'' sealing the crack. Sudden opening of the valve generates the broadband infrasonic signal and simultaneously triggers the collapse of the crack, initiating resonance of the remaining fluid. Subtle waveform and amplitude variability of the infrasonic signals as recorded at an array 13.4 km to the NW of the volcano are attributed primarily to atmospheric boundary layer propagation effects, superimposed upon amplitude changes at the source.Citation: Matoza, R.

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“…Infrasound travels 68 up to thermospheric altitudes of 120 km and ex-69 periences refractions due to an increase in wind 70 and/or temperature as a function of altitude. 71 If the gradients in the propagation velocity are 72 strong enough, infrasound will be sent back to the 73 Earth's surface (Drob et al 2003). There are three 74 regions in the atmosphere where such gradients 75 might exist.…”

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confidence: 99%