Meteorological tsunamis on the Pacific coast of North America

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Meteorological tsunamis on the Pacific coast of
North America

• Fine I.V..1,2, Thomson R.E.1 , Rabinovich A.B.1,3

1 Institute of Ocean Sciences, Sidney, Canada 2
Heat and Mass Transfer Institute, Minsk,
Belarus 3 Shirshov Institute of Oceanology,
Moscow, Russia
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Contents

• 1. Introduction Tsunamis and meteotsunamis
• 2. Observations
• - 9 December 2005
• - 13 July 2007
• - 26 February 2008
• 3. Model Energetic of the wave generation, major
  mechanisms and effects
• 4. Conclusions

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Rissaga waves in Ciutadella Harbour (Menorca
I.) 15 June 2006
More than 40 damaged boats. Total loss 30 mln
euros.
(Montserrat, Vilibic, and Rabinovich, 2006)
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Vela Luka, Croatia, 21 June 1978
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Observational sites on the coast of British
Columbia and Washington State
Tofino
Pat. Bay
Bamfield
Victoria
Neah Bay
La Push
Seattle
Tacoma
Longview
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Tsunami-like event recorded on 9 December 2009 on
the coast of British Columbia There were no
seismic activity nor strong storm in the region.

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Later we found an atmospheric pressure record at
La Push showing that the event was forced by an
abrupt jump of atmospheric pressure (2 mb).
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Tsunami-like event on 13 July 2007 recorded at
tide gages of the WA and BC coast in the Golf
area.
Sea level
All records have a clear arrival time.
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Tsunami-like event on 13 July 2007 recorded at
tide gages of the WA and BC coast in the Golf
area.
Sea level
Atmospheric pressure
All records have a clear arrival
time. Atmosphreric disturbances were on nigth
time of 13 July and repeated on 15 July 15 with
less intersity.
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We analyzed atmospheric pressure records and
found the event was forced by disturbance moving
northward with speed about 23 m/s
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Additional high resolution microbarograph records
in the Greater Victoria Area confirmed the
previous estimates.
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Comparison of the tide gauge record at Patricia
Bay and atmospheric pressure record at the nearby
microbarograph station. Sea level and
atmospheric variations started almost
simultaneously
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The direction and the speed of the moving
atmospheric disturbances are in good agreement
with the direction and speed of the jet stream in
the area of interest.
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Tsunami-like event on 26 February 2008 recorded
at tide gages of the WA and BC coast in the Golf
area.
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The direction (toward east-north) and the speed
(30 m/s) of the moving atmospheric disturbances
are also in good agreement with direction and
speed of the jet stream in the area of interest.
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Model

• Similarly to a seismological tsunami, a
  meteotsunami is forced by a term in the mass
  conservation equation

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Energy generation
Wave energy is generated due to the hysteresis
effect. In a stationary case, when the
atmospheric disturbance moves with a constant
velocity, the wave energy is not
generated. However, in a non-stationary case the
energy is generated permanently feeding
propagating waves.
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Proudman resonance
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Bathymetry map of the central part of the area
Supersonic (red) and subsonic (blue) areas
for U30 m/s
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The areas of the active energy generation
Meteotsunami modelling The disturbance moves to
the north
30 m/s
20 m/s
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Simulated records at specific locations
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The simulated energy as function of atmospheric
parameters
The total generated energy (over the entire
region) is nearly isotropic. The atmospheric
speed is the major factor
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Conclusions

• 1. Meteotsunamis are relatively frequent
  phenomena on the west coast of the US and
  Canada.
• 2.Meteotsunami in the area are mainly caused by
  fast moving (20 30 m/s) atmospheric
  disturbances of 1-3 mb with periods of 5 min 2
  hrs.
• 3. High atmospheric activity (small-scale
  disturbances and buoyancy waves) may last hours
  and even days. The speed and direction of the
  disturbances correlate well with the speed and
  direction of the atmospheric jet stream.
• 4. Mountains and instability conditions
  (occurring mainly the night time in summer) are
  additional important factors stimulating the
  process.

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• 5. The efficiency of the wave energy generation
  is related to the Proudman resonance with the
  atmospheric disturbance speed of 20-30 m/s most
  of energy is generated at depths of 40-90 m.
• 6. The direction and peak period of the
  atmospheric disturbance propagation are the
  secondary factors influencing the total amount of
  energy generated in the area. For some sites
  these factors can play the crucial role.

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Thank you!