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Hurricane Studies Using Infrasound

Hurricane Studies Using Infrasound. Claus Hetzer 1 , Roger Waxler 1 , Carrick Talmadge 1 , Milton Garces 2 , Ken Gilbert 1 , Henry Bass 1 1 National Center for Physical Acoustics The University of Mississippi 2 Infrasound Laboratory The University of Hawaii, Manoa.

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Hurricane Studies Using Infrasound

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  1. Hurricane Studies Using Infrasound Claus Hetzer1, Roger Waxler1, Carrick Talmadge1, Milton Garces2, Ken Gilbert1, Henry Bass1 1National Center for Physical Acoustics The University of Mississippi 2Infrasound Laboratory The University of Hawaii, Manoa Distribution A – Approved for public release; distribution unlimited.

  2. Hurricanes pose great danger to coastal communities Hurricane warnings often are not trusted and thus ignored Forecast of storm intensity at landfall particularly difficult Great interest in accurate remote sensing of hurricanes to improve short-term forecasting Hurricane Readiness

  3. Hurricanes known to produce infrasound in microbarom band Microbaroms generated by nonlinear interaction of oppositely-directed ocean surface waves Infrasonic observations include Kirogi, Carlotta (2000), Daniel (2001), Adeline-Juliet, Katrina, Ophelia (2005), Usagi (2007) On gross scale, signal azimuths point at storm Hurricane Infrasound: Microbaroms

  4. Typhoon Usagi (2007) Palau: Lat 7.5N

  5. Typhoon Usagi (2007) Detections consistently behind storm Atmospheric modeling predicts < 5° deviation

  6. Cyclone Adeline-Juliet (2005)

  7. Cyclone Adeline-Juliet (2005) Detections track storm roughly, but rarely point at eye

  8. Hurricane Fabian (2003) Highest-intensity microseisms happen after storm passes the station!

  9. Some questions exist regarding the location of the infrasound source region All models require a mechanism for producing opposing wavetrains Proposed models generally take into account only waves generated by storm winds, i.e. Tabulevich (right) Microbarom Source Region

  10. Microbaroms may be generated by the interaction between storm waves and the ambient wave field This interaction can produce opposing swells hundreds of kilometers from the storm eye In agreement with previous and current work (Garces, Willis, Chevrot) More Inclusive Model

  11. Fine detail from wave models may not be reliable, but general trends of opposition are evident Implication: acoustic modeling/monitoring of hurricanes requires knowledge of ambient wave field This may be nontrivial in near-landfall situations More Inclusive Model

  12. Usagi: Pristine Case

  13. Adeline-Juliet: More Complicated

  14. Conclusions • Microbarom bearing data for two observed hurricanes is seen to deviate from point of highest winds • This appears to be a result of interactions with the ambient surface wave field, in agreement with microbarom theory and previous/current work • Acoustic studies and models of hurricanes must take the ambient wave field into account • This analysis should be expanded to as many known infrasound recordings of hurricanes as possible, particular from island stations

  15. Next Steps • More storms, more stations! • Start running WaveWatch III model – higher resolution? • Separate out source, propagation, array components of azimuth scatter • Relationship: Δaz(Wstorm,Wambient)

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