Abstract
An infrasound field campaign was performed in 2011/2012 utilizing single infrasound sensors along the great circle path between a known ground-truth source (Ariane 5 engine test facility, Lampoldshausen, Germany) and a regional receiver (German infrasound array IS26, Bavarian Forest) covering a distance of rough 320 km in total. The gathered recordings provide new insights in the infrasonic wave propagation at regional and near-source distances by comparing measured signals with modeling results within this study. Ray-tracing and parabolic equation approaches are utilized to model infrasound propagation from the ground-truth source to the line profile sensors and explain the obtained detections and non-detections. Modeling and observation results are compared by estimating their amplitude, quantifying amplitude deviations and also considering observed and calculated travel times and celerities. Modeling results show a significant influence of small-scale atmospheric variations in effective sound speed profiles on the propagation pattern, which results in varying tropospheric and stratospheric ducting behavior. A large number of gravity wave profiles are tested to investigate the influences of atmospheric dynamics on the infrasound wave field and improve the modeling results. The modeling is furthermore applied to a case of two potential, contemporaneous and closely spaced infrasound sources. Propagation modeling is used here to resolve the source ambiguity between a ground-based and a higher altitude source giving a strong preference to the latter with respect to the observed infrasonic signatures. The good agreement between modeling and observation results within this study successfully shows the benefit of applying infrasound propagation modeling to the validation of infrasound measurements, verification of ducting behavior and discrimination of infrasound sources.
Highlights
Infrasound is generated by a variety of different natural and artificial sources such as volcanic eruptions or meteorite entries [1,2,3] and anthropogenic events such as aircraft/spacecraft signatures or explosions [4,5,6], respectively
In a previous study [23], infrasound signals were analyzed from Ariane 5 engine tests in the years 2000-2004 that could be identified at station IS26 of the International Monitoring System (IMS) network of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO)
Infrasound propagation modeling within this study was applied to a number of ground-truth field campaign measurements: a total of nine rocket engine test cases and two additional source scenarios
Summary
Infrasound is generated by a variety of different natural and artificial sources such as volcanic eruptions or meteorite entries [1,2,3] and anthropogenic events such as aircraft/spacecraft signatures or explosions [4,5,6], respectively. Propagation modeling is applied in this study to verify ducting from a known ground-truth source to a receiver and to discriminate between different potential sources of a signature, taking into consideration atmospheric conditions and small-scale changes on the propagation path. Certain detections and their observed travel-time and celerity values can only be explained by including unusual propagation conditions, near-field tropospheric ducting and small-scale atmospheric perturbations such as gravity waves [19,20,21,22].
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