Paul McWilliams

1
Exploring Puget Sound Tides Currentswith the

• Acoustic Doppler Current Profiler (ADCP)
• Paul A. McWilliams

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Presentation Outline

• Tides (Sat Fri)
• Predicted Currents
• The ADCP
• Data Samples
• Contours
• Profiles
• Questions

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Tides for 8 14 May, 2004

• Saturday May 8
• Spring Ebb
• Range13.3ft
• Low 207 AM 7.2
• High 653 AM 10.4
• Low 217 PM -2.9
• High 1004 PM 11.5
• Maximum Ebb 1036AM

• Friday May 14
• Neap Flood LHW
• Tidal Range5.2ft
• High 233 AM 11.1
• Low 910 AM 2.8
• High 310 PM 8.0
• Low 833 PM 3.5
• Max Flood 1213pm

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Ebb Tide (Sat)

• Expected Flow
• North in central Puget Sound
• South from Possession Sound
• West Through Admiralty Inlet

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Flood Tide (Fri)

• Expected Currents
• East through Admiralty Inlet
• South in Central Sound
• North in Possession Sound

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Current Predictions

• Saturday May 8
• Stronger Currents
• Northward Flow during Ebb Tide
• Westward Flow in the near Edmonds

• Friday May 14
• Weaker Currents
• Southward flow during Flood Tide

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Acoustic Doppler Current Profiler (ADCP)

• Uses compression and expansion of reflected
  sound-waves to measure the movement of particles
  in the water
• Requires significant Processing
  power-Microprocessors Make Possible
• Must take Ships Motion into account (GPS)

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ADCP Limitations

• Cannot see bottom 15 of Water Depth or Near
  Surface
• Backscatter
• Surface Noise
• GPS PrecisionShips Pitch and Roll not Accounted
  For

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Three Types of Displays

• Contour
• Detail Contour
• Profile

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6 Types of Data

• Direction
• Magnitude
• North Velocity
• East Velocity
• Error
• Vertical

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GPS Navigation Processing
Friday PM leg Contours without and with (bottom)
Navigation Processing
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Direction Contours

• Sat (Top)
• versus
• Fri (Bottom)
• Color Code
• MagentaNorth
• BlueEast
• GreenSouth
• OrangeWest

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Magnitude Contours

• Saturday (top)
• Versus
• Friday (bottom)
• Color Code
• Magnitude (mm/s)
• Red700
• Blue0

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North Velocity

• Saturday (top)
• Versus
• Friday (Bottom)
• Color Code
• Warmor N
• Coolor S
• /-700mm/s

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East Velocity

• Saturday (top)
• Versus
• Friday (Bottom)
• Color Code
• Warmor E
• Coolor W
• /-700mm/s

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Profile Examples-Max Ebb

• Saturday
• Taken _at_ West Point
• 1036am
• Velocity
• GreenN
• RedEast

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Profile Examples-Max Flood

• Friday
• Taken _at_ Edmonds
• 1213pm
• Velocity
• GreenN
• RedEast

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Profile Examples-Friday Cast 3

• Friday
• Taken _at_
• ORCA 2
• 340pm
• (high slack)
• Velocity
• GreenN
• RedEast

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Questions?

• For More Information
• http//students.washington.edu/paulmcqm/ocean_crui
  se.htm

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Conclusions

• Predictions seems accurate
• ADCP seems to work
• Currents are strongly tide based
• Point Wells seems okay for discharge
• Need to look at
• full range of tides
• Storm conditions