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http://www.warmwinds.com/surf-cam/
http://www.surfermag.com/videos/pipeline-aerial-perspective/
http://www.surfline.com/surf-report/backwash-southern-baja_60714/
Stirred by the winds into waves and pulled up and down by tidal forces, the ocean surface is always in motion.
Waves are among the most common and easily observed ocean phenomena.
Waves are periodic and predictable if the amount of energy applies to the ocean is known.
Predictable wind, earthquakes, turbidity currents, landslides, friction, and the pull of the sun and the moon all generate waves.
The sun and the moon generate the largest waves of all: the tides.
Waves
Waves are energy transmitted through matter◦ The medium ( solid, liquid, gas) not actually travel
as the energy passes through it, but its constituent particles vibrate or oscillate in place as the energy passes through them.
Definition of a wave
Longitudinal waves (push-pull) – sound waves, the particles that are in vibratory motion push and pull in the same direction the energy is traveling.◦ Wave form travels through the medium by
compressing and decompressing
Waves
Transverse wave (side to side ) – energy travels at right angles to the direction of particle vibration◦ Generally transmits energy only through solids because
only in a solid are particles strongly bond to one another◦ These are called body waves because they transfer
energy though a body of matter
Waves
Orbital waves – waves that transmit energy along an interface between two fluids of different densities◦ Particle movements are neither longitudinal nor
transverse◦ Example: interface between the atmosphere and the
ocean. The movement of particles along such an interface involves components of both longitudinal and transverse waves because the particles move in circular orbits.
Waves
As a wave passes to the right, the motion of a floating rubber ducky resembles that of a circle, which is known as circular orbital motion
Orbital Wave
Crest – high parts of waves
Trough – low part of waves
Wave height (H) – vertical distance between the trough and crest
Wave length (L) – horizontal distance between two corresponding points
Wave steepness- H/L
Wave Characteristics
Wave period – time (in seconds) that elapses during the passing of one full wave, or wavelength
Wave frequency- the number of wavelengths that pass a fixed point per unit of time
Amplitude- Distance from level of crest to level of trough
Wave Characteristics
Shallow-Water Waves Depth of water is above wave base, way above. (depth
< 1/20 wave length)
Waves and Water Depth
Transitional Waves (Between Deep and Shallow) Depth is above wave base, but only a little. (1/2 wavelength > depth > 1/20 wave length)
Waves and Water Depth
Recall:◦
◦ Wave Base = ½ Wave Length
Think: What happens if the Wave Base is decreased? How does that effect Wave Speed?
Breaking Steepness = 1/7 = H/L
Effect of Decreasing Depth
Capillary Waves The little guys
You’ve seen these on Lucky Peak
Gravity Waves Can be huge
You’ve seen these in videos of the ocean, probably not on a lake.
Breaking waves AKA: White Caps Also on the shore Any time the steepness is larger than what?
Wave Size
Wind Generated WavesFactors important to
increasing the amount of energy transferred to the waves are:
1. The wind speed2. The duration – the
length of time during which the wind blows in one direction
3. The fetch – the distance over which the wind blows in one direction
Wind Generated WavesThe energy of a wave is directly related to
wave heightAs sea waves gain energy, their steepness
increases When steepness reaches a critical value of 1/7,
open ocean breakers called whitecaps form
Swells from different storms run together, the waves clash, or interfere with one another
Interference
Starts as a capillary wave in open sea. Grows to a gravity wave. The storm surges The swell distances itself from the storm Carries energy (in the form of waves) across
the open sea.◦ Can cause interference across the open sea
As deep water swell moves toward shore (shoaling) it enters the surf
Energy in the wave dissipates when the wave breaks.
Life cycle of a wave
Physical Changes as waves approach shore
As deep water waves of swell move toward continental margins over shoaling water, they eventually encounter water depths that are less than one-half of their wavelength
Physical Changes as waves approach shore
S waves come into shallow water and fell bottom, their speed and wavelength decrease while their wave height and wave steepness increase, this action causes waves to break
Breaking waves are analogous to a person who leans too far forward.
BreakersSpilling breakers – is a turbulent mass of air and
water that runs down the front slope of the wave as it breaks
Plunging breaker – has a curling crest that moves over an air pocket
Surging breaker- build up and break right at the shoreline.
Rogue Waves
Massive waves that can reach 10 stories highImpossible to predict occurrence, main cause
of rogue waves is theorized to be extraordinary constructive interference
Rouge waves: Think they are Dangerous?
Some Rare Waves
http://www.youtube.com/watch?v=l_8hOai9hGQ
Breaking Steepness = 1/7 = H/L If length decreases, and height increases, what
happens to steepness?
Refracting Waves If the shore is not straight, how does the differing
speed effect the apparent direction of the wave?
Effect of Decreasing Speed
What are mechanical waves? What do they do?
What are they? Two – or three types.
Really there are only two but when combined they make a third that’s kind cool and that’s what ocean waves are, well, not all water waves, just the ones that we are used to seeing, I mean a tsunami is a wave, and made of water, and in the ocean, but its not an ocean wave, ocean waves are something more specific, and tsunamis aren’t the third kind of wave so much… But, all waves do the same thing, and what do they do?
Review! What are the TWO types of waves? What do they add up to? Which is an ocean wave? What are some parts of a wave? How deep does the motion of a wave go?
Ocean Waves Atmospheric waves Internal waves – “desk
top oceans” Where do these happen?
Splash Waves Tides Tsunami Human Induced
Types of waves
Tsunami Storm Surge Swell Shoaling Fetch Wave train Rouge Waves Breaking Waves Interference
Refracting Waves Reflecting Diffracting Gravity Waves Capillary Waves Transitional Waves Shallow-Water Waves Deep-Water Waves
Words to know:
Types of waves Waves and Water Depth
Deep-Water Waves Shallow-Water Waves Transitional Waves
Breaking Steepness = 1/7 = H/L Refracting Waves
The Cause – Wind – fig 9.8, table 9-1, Capillary Waves
Restoring force Gravity Waves Breaking Waves Life of a Wave
Rarities Rouge Waves
Interference Wave train Tsunami
What we covered today:
Create a diagram of a Wave Train which is shoaling.
Label the following parts: Crest Trough Wave length Wave height Still water level Wave Base
Open water waves Deep water waves Transitional waves Shallow water waves Breaking waves
Task to be done: