1. Waves
Chapter 9

2. Study Plan 9.1 Ocean waves move energy across the sea surface
9.2 Waves are classified by their physical characteristics
9.3 The behavior of waves is influenced by the depth of water through which they are moving

3. Study Plan 9.4 Wind blowing over the ocean generates waves
9.5 Interference produces irregular wave motions
9.6 Deep-water waves change to shallow-water waves as they approach the shore

4. Study Plan 9.8 “Tidal waves” are probably not what you think
9.9 Storm surges form beneath strong cyclonic storms
9.10 Water can rock in a confined basin
9.11 Water displacement causes tsunami and seismic sea waves

5. What is a wave?
A Wave is a rhythmic movement that carries energy through matter or space.
In oceans, waves move through seawater

6. Parts of the wave Crest – highest point of a wave
Trough – lowest point of a wave
Wave Height – vertical distance between the crest and the trough
Wavelength – horizontal distance between two crests or two troughs

7. Wavelength
Crest
Wave Height
Still Water
Trough
Wave Parts

8. 9.1 Ocean waves move energy across the sea surface
Orbit: Energy transfer from water particle to water particle
Orbital wave: a wave in which particles of water move in closed circles as the wave passes
progressive wave: the wave moves forward

9. Period and frequency
Period: the time it takes for a wave to move a distance of one wavelength
Frequency: number of waves passing a fixed point per second

10. 9.2 Waves are classified by their physical characteristics
Ocean waves are formed by a disturbing force (energy that causes ocean waves to form)
Waves are weakened by a restoring force (returns the wave to flatness after a wave has formed in it)
Wavelength is the most useful measure of a wave size

11. Idealized Wave Spectrum

12. 9.3 The behavior of waves is influenced by the depth of water through which they are moving

13. Orbit Diameter and Stokes Drift

14. Wave base is the depth to which a surface wave can move water.
Wave Motions
Wave base is the depth to which a surface wave can move water.
If the water is deeper than wave base, orbits are circular and there is no interaction between the bottom and the wave. If the water is shallower than wave base, orbits are elliptical and become increasingly flattened towards the bottom.

15. Deep- and Shallow-Water Motion

16. Celerity is the velocity of the wave form and not of the water.
Wave Motions
There are three types of waves defined by water depth: Deep-water wave, Intermediate-water wave, and Shallow-water wave.
Celerity is the velocity of the wave form and not of the water.
The celerity of a group of waves all traveling at the same speed in the same direction is less than the speed of individual waves within the group.

17. Celerity
C = L / T
Speed of the wave
L = wavelength
T = time or period

18. 9.4 Wind blowing over the ocean generates waves
Wind waves are gravity waves formed by the transfer of wind energy into the water

19. Capillary wave

20. Fetch is the area of contact between the wind and the water and is where wind-generated waves begin.
Seas is the term applied to the sea state of the fetch when there is a chaotic jumble of new waves.
Waves continue to grow until the sea is fully developed (3 days of wind) or becomes limited by fetch restriction or wind duration.

21. Waves Caused by Wind
When wind blows across a body of water, friction causes the water to move along with the wind.
Wave Height depends on –
Wind speed
Distance over which the wind blows
Length of time the wind blows

22. 9.5 Interference produces irregular wave motions
Constructive vs. destructive interference

23. Wind waves can grow to enormous Size
7 Feb 1933
For days, wind was blowing at 67 MPH (107 kph)

26. 34 m (112 ft)!!!

28. 9.6 Deep-water waves change to shallow-water waves as they approach the shore

30. Wave Movement
When a wave breaks against the shore, the crest outruns the trough and the crest collapses.
Called a breaker.
In this case, water does move forward and backward.

32. S
Wave Refraction

33. S

34. P

35. S
Convergence
Divergence

36. 9.8 “Tidal waves” are probably not what you think

37. 9.9 Storm surges form beneath strong cyclonic storms

38. Storm surge is the rise in sea level resulting from low atmospheric pressure and the accumulation of water driven shoreward by storm winds.
Water is deeper at the shore area, allowing waves to progress farther inland.
Storm surge is especially severe when superimposed upon a spring high tide.

39. 9.11 Water displacement causes tsunami and seismic sea waves
“Tsunami” – “harbor wave” or seismic sea wave

40. Tsunami are always shallow-water wave
26 Dec 2004, Indian Ocean
Wavelength: up to 200 km (125 mi)
470 MPH (212 m / s)
5 hours to get to Alaska!!!

43. Tides

44. What causes tides?
The gravitational forces of the moon and sun on the water causes the tides..
The moon, being nearest, has the greatest effect even though the sun is the larger of the two.
High tides are generated on the sides of the Earth nearest to and farthest from the moon

45. During new and full moon phases the moon, sun, and Earth are aligned causing a greater gravitational pull on the Earth.
This results in higher high tides and lower low tides.

46. How are Tides Predicted?