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Tsunami-Generated Atmospheric Gravity Waves
Key words: wave-mean interaction, waves in shear, differential equation solver, stochastic methods
Motivation
Motivation
Tsunamis are hard to detect in the open ocean but can be devastating when approaching the coast.
One possible early detecting technique is to monitor the atmospheric perturbations induced by the sea-level change due to tsunamis.
Studying the propagation of tsunami-generated atmospheric gravity waves is of central importance for tsunami early detection using ionospheric sounding techniques.
tsunami indonesia2004.mov
Research Goals
Research Goals
Examine the generation, propagation, and partial transmission/reflection of Acoustic-Gravity Waves (AGWs) in background wind shear and varying stratification
Quantify the effects of winds and compressibility of the atmosphere on wave transmission and reflection
Answer how soon and how much energy carried by AGWs will reach the lower ionosphere
Key Findings
Key Findings
Wave transmission and reflection
Wave transmission and reflection
Partial transmission (middle row) and reflection (bottom row) of tsunami-generated gravity waves in anelastic (left column) and compressible (right column) atmosphere with a wind jet centered at 100 km altitude (Wu et al. 2016).
Strong vertical shear in the wind jet Doppler-shifts gravity waves into evanescence between roughly 80−120 km altitude. At turning points where the vertical wavenumber is zero, waves are reflected downward.
Energy partition
Energy partition
The transmitted and reflected fractions of wave kinetic energy have been expressed as a function of (tsunami) horizontal wavenumber, i.e., T(k) and R(k), respectively.
Waves with larger horizontal scales have a greater ability to reach the upper boundary, i.e., the lower ionosphere, and to be detected by remote sensing techniques.
Time dependency
Time dependency
Time evolution of the normalized vertical displacement at 100 km altitude due to upward-propagating gravity waves. The effects of atmospheric conditions are explored.
Early-stage wave perturbations (orange curve in the first 40 minutes after the tsunami event) are observed in a compressible atmosphere due to the arrival of fast acoustic waves, but are not present in the anelastic case.
Publications
Publications
Wu, Y., S. G. Llewellyn Smith, J. W. Rottman, D. Broutman, J.-B. H. Minster, 2020: Time-dependent propagation of tsunami-generated acoustic-gravity waves in the atmosphere. Journal of the Atmospheric Sciences, 77(4), 1233-1244. Link
Wu, Y., S. G. Llewellyn Smith, J. W. Rottman, D. Broutman, J.-B. H. Minster, 2016: The three-dimensional propagation of tsunami-generated internal waves in the atmosphere. International Symposium on Stratified Flows, 1(1). Link
Wu, Y., S. G. Llewellyn Smith, J. W. Rottman, D. Broutman, J.-B. H. Minster, 2016: The propagation of tsunami-generated acoustic-gravity waves in the atmosphere. Journal of the Atmospheric Sciences, 73(8), 3025-3036. Link
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