1. Chapter 10
Waves

2. Wave Formation Generating Force Restoring Force Surface tension
Gravity

3. Wave Formation Gravity waves Generating Force Wind Ripples
Capillary waves
Cat’s-paws

4. Anatomy of a Wave Crest Trough Wavelength (L) Wave height (H)
Amplitude = 1/2H
Period (T)
Seconds/cycle
Frequency
Cycles/second

5. Wave Motion
As waves pass, wave form and wave energy move rapidly forward, not the water!
Two basic motions associated with waves:
Forward motion
Orbital motion

6. Orbital Motion
As wave approaches, a water particle will trace a circular path
Diameter of orbit at surface = wave height

7. Wave Base
Wave particle orbits are not detectable below ~1/2 wavelength

8. Wave Speed Celerity (C) Period remains the same C = wavelength/period
C = L/T
Period remains the same

9. Wave Measurement
The simplest technique is to examine the oscillation of waves against a pole fixed marked in meters
Oceanographers will employ pressure sensors anchored to the sea floor

10. Wave Measurement
Satellite Imagery

11. Deep-water Waves
Waves that propagate in water than is one-half their wavelength
Wave base is above the sea floor

12. Deep-water Waves L = (g/2π)T2 L = (1.56 m/sec2)T2 L/T = (1.56 m/sec2)T
C2 = 1.56L

13. Storm Centers Progressive wind waves (PWW’s) Wind Gravity
Propagate in particular direction

14. Storm Centers Progressive wind waves (PWW’s) Confused seas
Forced waves

15. Dispersion Free waves No longer wind-driven waves
Period does not change

16. Group Speed Wave Train Group Speed (V)
One-half the wave velocity for deep-water waves
V = C/2

17. Constructive Wave Interference
Crests & troughs coincide
Build up of crest & deepening of trough

18. Destructive Wave Interference
Crest of one wave coincides with trough of another wave (and vice versa)
Dampening of wave

20. Wave Height
The variety and size of wave generated depends on 3 factors:
Speed of the wind
How long the wind blows
Size of the fetch of the wind

21. Wave Height 40-50o S Typical maximum fetch Ideal wave production
No landmasses to limit fetch
Westerlies
Typical maximum fetch
920 km (500 miles)

22. Wave Height
Larger waves will be produced on the side of the storm where the winds are blowing in the same direction as the storm is moving
10-15 m (33-49 ft)
m ( ft) long

23. Wave Height Episodic waves
Produced as a result of constructive interference
Occur most often near edge of continental shelf
20-30 m
50 knots