Paul McWilliams – Ocean 101Spring 2004

Exploring Puget Sound Tides & Currents

with the

Acoustic Doppler Current Profiler (ADCP)

Paul A. McWilliams

Paul McWilliams – Ocean 101Spring 2004

Presentation Outline

1. Tides (Sat & Fri)2. Predicted Currents3. The ADCP4. Data Samples

• Contours• Profiles

5. Questions

Paul McWilliams – Ocean 101Spring 2004

Tides for 8 &14 May, 2004

Saturday May 8• Spring Ebb• Range=13.3ftLow 2:07 AM 7.2

High 6:53 AM 10.4

Low 2:17 PM -2.9

High 10:04 PM 11.5

Maximum Ebb ~10:36AM

Friday May 14• Neap Flood &

LHW• Tidal Range=5.2ftHigh 2:33 AM 11.1

Low 9:10 AM 2.8

High 3:10 PM 8.0

Low 8:33 PM 3.5

Max Flood ~12:13pm

Paul McWilliams – Ocean 101Spring 2004

Ebb Tide (Sat)

Expected Flow• North in central

Puget Sound• South from

Possession Sound• West Through

Admiralty Inlet

Paul McWilliams – Ocean 101Spring 2004

Flood Tide (Fri)

Expected Currents• East through

Admiralty Inlet• South in Central

Sound• North in

Possession Sound

Paul McWilliams – Ocean 101Spring 2004

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

Paul McWilliams – Ocean 101Spring 2004

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 Ship’s Motion into account (GPS)

Paul McWilliams – Ocean 101Spring 2004

ADCP Limitations

• Cannot “see” bottom 15% of Water Depth or Near Surface– Backscatter– Surface Noise

• GPS Precision—Ship’s Pitch and Roll not Accounted For

Paul McWilliams – Ocean 101Spring 2004

Three Types of Displays

• Contour• Detail Contour• Profile

Paul McWilliams – Ocean 101Spring 2004

6 Types of Data

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

Paul McWilliams – Ocean 101Spring 2004

GPS Navigation Processing

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

Paul McWilliams – Ocean 101Spring 2004

Direction Contours

Sat (Top)versusFri (Bottom)

Color Code:Magenta=North

Blue=East

Green=South

Orange=West

Paul McWilliams – Ocean 101Spring 2004

Magnitude Contours

Saturday (top)VersusFriday

(bottom)

Color Code:

Magnitude (mm/s)

Red=700

Blue=0

Paul McWilliams – Ocean 101Spring 2004

North Velocity

Saturday (top)VersusFriday

(Bottom)

Color Code:Warm=“+”or N

Cool=“–”or S

+/-700mm/s

Paul McWilliams – Ocean 101Spring 2004

East Velocity

Saturday (top)VersusFriday (Bottom)

Color Code:Warm=“+”or E

Cool=“–”or W

+/-700mm/s

Paul McWilliams – Ocean 101Spring 2004

Profile Examples-Max Ebb

• Saturday • Taken @ West

Point• 10:36am

VelocityGreen”+”=N

Red”+”=East

Paul McWilliams – Ocean 101Spring 2004

Profile Examples-Max Flood

• Friday • Taken @

Edmonds• 12:13pm

VelocityGreen”+”=N

Red”+”=East

Paul McWilliams – Ocean 101Spring 2004

Profile Examples-Friday Cast 3

• Friday • Taken @ ORCA 2• 3:40pm (high slack)VelocityGreen”+”=N

Red”+”=East

Paul McWilliams – Ocean 101Spring 2004

Questions?

For More Information:http://students.washington.edu/paulmcqm/

ocean_cruise.htm

Paul McWilliams – Ocean 101Spring 2004

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