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Acoustic waveform inversion with application to seasonal snow covers
1US Army Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire 03755-1290, USA. dalbert@crrel.usace.army.mil
The Journal of the Acoustical Society of America
|February 24, 2001
Summary
Atmospheric acoustic pulses change significantly when traveling over snow due to air in pores. A time-domain method accurately determined snow properties like flow resistivity and depth from these acoustic signals.
Area of Science:
- Acoustics
- Geophysics
- Environmental Science
Background:
- Atmospheric acoustic pulses undergo significant amplitude and waveform changes when propagating over seasonal snow cover.
- This interaction is caused by air forced into snow pores, reducing pulse amplitude and elongating waveforms compared to other ground surfaces.
Purpose of the Study:
- To investigate variations in snow-cover effects on acoustic pulse propagation.
- To develop and compare inversion procedures for determining snow-cover parameters from acoustic data.
Main Methods:
- Recorded acoustic pulses propagating horizontally over 11 different natural snow covers over two winters.
- Developed two inversion procedures: a frequency-domain technique and a time-domain minimization method.
- Utilized the time-domain method for its unique solutions and excellent waveform agreement.
Main Results:
- The effective flow resistivity and snow depth were identified as primary parameters controlling waveform shape.
- Pore shape factor ratio was found to be of secondary importance.
- Inversion estimates yielded flow resistivities from 11 to 29 kN s m(-4), with higher values in late-season snow.
- Acoustically determined snow depths generally agreed with measured values.
Conclusions:
- The time-domain inversion method provides accurate and unique solutions for snow-cover parameters.
- Flow resistivity and snow depth are key factors influencing acoustic pulse propagation over snow.
- Pore shape factor ratio can distinguish between wet and dry snow conditions.
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