Waves and things. Homework Due Tuesday Read Pages 52-55. Answer in complete sentences What causes the Coriolis effect? How does the Coriolis effect wind.

Waves and things

Homework Due Tuesday• Read Pages 52-55. Answer in complete sentences• What causes the Coriolis effect?• How does the Coriolis effect wind in the northern

hemisphere? How is that different than its affect in the southern hemisphere?

• How does the Ekman Spirial relate wind speed to water depth?

• What do Gyers do? What does the book mean when it says “(Gyers) act like a giant thermostat”?

• What happens when waves “pile up” ? What do you call it when they fall forward and break? Where is the wave’s energy transferred to when the wave breaks?

• The oceans are in constant motion. The oceans are in constant motion. The most obvious examples of this The most obvious examples of this along the shoreline are waves. In along the shoreline are waves. In this lecture we will learn about:this lecture we will learn about:

– The properties of ocean wavesThe properties of ocean waves– Wind generation of wavesWind generation of waves– Wave motionWave motion– The life history of ocean wavesThe life history of ocean waves– Beach and shoreline processesBeach and shoreline processes– Waves behave like………wavesWaves behave like………waves

Properties of Ocean WavesProperties of Ocean Waves

Properties of Ocean WavesProperties of Ocean Waves

• An ocean wave is an undulation of the sea An ocean wave is an undulation of the sea surface. Important wave terms to know:surface. Important wave terms to know:– Wave crest – The top of the waveWave crest – The top of the wave– Wave trough- The bottom of the waveWave trough- The bottom of the wave– Wave height-measure between crest and troughWave height-measure between crest and trough– Wavelength – measure between crestsWavelength – measure between crests– Wave period – time it takes for a wave to move Wave period – time it takes for a wave to move

past a given pointpast a given point

• Progressive waves Progressive waves move across the sea surface.move across the sea surface.

• Standing waves Standing waves oscillate about a fixed point.oscillate about a fixed point.

Parts of a Wave

The “top” of the wave is the The “top” of the wave is the

Wavelength

Crest

Trough

Period

0% 0%0%

100%1.1.WavelengthWavelength

2.2.Crest Crest

3.3.TroughTrough

4.4.PeriodPeriod

The “bottom” of the wave is The “bottom” of the wave is thethe

Trough

Crest

Wavelength

Period

100%

0%0%0%

1.1.TroughTrough

2.2.CrestCrest

3.3.WavelengthWavelength

4.4.PeriodPeriod

The distance between the The distance between the crests is thecrests is the

Period

Crest

Amplitude

Wavelength

0%

95%

5%0%

1.1.PeriodPeriod

2.2.CrestCrest

3.3.AmplitudeAmplitude

4.4.WavelengthWavelength

Fastest Responders (in Fastest Responders (in seconds)seconds)

12.71 Brett Nelson

13.95 John Drenga

14.4 Alejandro Rivera

16.7 Brian Stam

• Waves are caused by different Waves are caused by different factors.factors.– WindWind– Submarine disturbances such as Submarine disturbances such as

earthquakes or landslides (tsunamis)earthquakes or landslides (tsunamis)– Gravitational attraction of sun and Gravitational attraction of sun and

moon (tides)moon (tides)

Wind Generation of WavesWind Generation of Waves• The size and character of wind-generated The size and character of wind-generated

ocean surface waves is determined by:ocean surface waves is determined by:

• Wind velocity – Wind SpeedWind velocity – Wind Speed– Wind duration – How long does it lastWind duration – How long does it last– Fetch - distance the wind blows over the Fetch - distance the wind blows over the

waterwater

• Simply put, wave size increases as the Simply put, wave size increases as the strength (speed) and duration of the wind, strength (speed) and duration of the wind, and distance over which it blows and distance over which it blows increases.increases.

The relationship between The relationship between wind speed and wave wind speed and wave heightheight

Wind Speed wave height period wave speedknots m s m/s

10 1.2 5.5 8.620 2.4 7.3 11.430 5.8 12.5 19.540 14.3 18 2850 16.8 21 32.8

Largest recorded storm Largest recorded storm wavewave

• height: 112 feet/34.2 mheight: 112 feet/34.2 m

• period: 14.8 speriod: 14.8 s

• speed: 90 ft/s/27 m/sec = 61 mphspeed: 90 ft/s/27 m/sec = 61 mph

• wavelength = 1100 ft/329 mwavelength = 1100 ft/329 m

The distance wind blows The distance wind blows over water is called theover water is called the

Crest

Dura

tion Fe

tch

Incli

ne

0% 0%

50%50%1.1.CrestCrest

2.2.DurationDuration

3.3.FetchFetch

4.4. InclineIncline

Waves height is determined Waves height is determined by wind speed, fetch and by wind speed, fetch and

Dire

ction

Temperatu

re

Dewpoint

Dura

tion

0%

100%

0%0%

1.1.DirectionDirection

2.2.TemperatureTemperature

3.3.DewpointDewpoint

4.4.DurationDuration

A landslide could cause a A landslide could cause a ______ wave ______ wave

Tide

Progre

ssive

Tsunami

50% 50%

0%

1.1.TideTide

2.2.ProgressiveProgressive

3.3.TsunamiTsunami

Fastest Responders (in Fastest Responders (in seconds)seconds)

2.95 Brett Nelson

7.55 Brian Stam

Wave MotionWave Motion

Wave Motion

• Wind-generated waves are progressive waves progressive waves because they travel

across the sea surface. There are two basic motions associated with an ocean wave:– the forward movement of the wave form– the orbital motion of water particles

beneath the wave• It is the wave energy not water

molecules themselves that moves across the sea surface.

Wave MotionThe motion of water particles beneath waves.

Forward Movement

Orbital movement

Wave Motion

• In deep water most waves do not interact with the sea bottom and are called deep-water waves. The orbits of the water molecules are circular.

• Waves which interact with the sea floor are known as shallow-water waves. The orbits of the water molecules become elliptical – friction, slow. (Shallow-water waves can occur in the deep ocean if the wavelength is long enough.)

WAVE DEPTHWAVE DEPTH

• Wave depth is one half of the Wave depth is one half of the wavelength.wavelength.

• If the wavelength is 20 meters the If the wavelength is 20 meters the depth is 10m depth is 10m

Life History of Ocean Wavesgetting closer to the shore…..

• In shallow water the sea bottom transforms the wave’s properties. transforms the wave’s properties.

• Bottom friction alters both– Wave form – Speed (Celerity)

The two types of motion The two types of motion found in waves arefound in waves are

Forw

ard and Ba..

.

Orb

ital a

nd Do...

Forw

ard and D

o...

Forw

ard and O

r...

0% 0%0%0%

1.1. Forward and Forward and BackwardBackward

2.2. Orbital and Orbital and DownwardDownward

3.3. Forward and Forward and DownwardDownward

4.4. Forward and Forward and OrbitalOrbital

Waves that interact with the Waves that interact with the ocean floor are calledocean floor are called

Shallo

w water .

..

Deep w

ater wav..

.

Orb

ital w

aves

Fetch

0% 0%0%0%

1.1.Shallow water Shallow water waveswaves

2.2.Deep water Deep water waveswaves

3.3.Orbital wavesOrbital waves

4.4.FetchFetch

Waves that do not interact Waves that do not interact with the ocean floor are with the ocean floor are calledcalled

Deep w

ater wav..

.

Shallo

w water .

..

Orb

ital w

aves

Fetch

0% 0%0%0%

1.1.Deep water Deep water waveswaves

2.2.Shallow water Shallow water waveswaves

3.3.Orbital wavesOrbital waves

4.4.FetchFetch

Fastest Responders (in Fastest Responders (in seconds)seconds)

0 Participant 1

0 Participant 2

0 Participant 3

0 Participant 4

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Racing Leader BoardRacing Leader Board

• As waves enter shallow waterAs waves enter shallow water– Wavelength shortensWavelength shortens– Height increasesHeight increases– Speed decreasesSpeed decreases

PERIOD REMAINS THE SAME

What is the one factor that determinesthe wave speed of shallow water waves?

DEPTH

Notice how wavesbunch together asthey approach shore.This is because thewaves in shallowerwater travel slower than the waves behindin deeper water.

FRICTION

Height increases

Speed Decreases

Wavelength Decreases

Deep/Shallow WavesDepth = 1/20th wavelength

Ocean bottom does not Ocean bottom does not affect the waveaffect the wave

The wave comes into The wave comes into contact with the bottom contact with the bottom and slows down the and slows down the wave. Wave height wave. Wave height increasesincreases

Top of wave Top of wave moves faster moves faster than the than the bottom of the bottom of the wave and the wave and the wave breakswave breaks

As a wave moves to shore As a wave moves to shore

Speed in

crease

...

Speed decre

ase...

Speed re

mains ...

0% 0%0%

1.1.Speed increasesSpeed increases

2.2.Speed Speed decreasesdecreases

3.3.Speed remains Speed remains the samethe same

As a wave moves to shoreAs a wave moves to shore

Heigh

t incre

as...

Heigh

t decre

as...

Heigh

t remains..

.

0% 0%0%

1.1.Height increasesHeight increases

2.2.Height Height decreasesdecreases

3.3.Height remains Height remains the samethe same

As a wave moves to shoreAs a wave moves to shore

Period in

creas

...

Period decre

as...

Period re

mains...

0% 0%0%

1.1.Period increasesPeriod increases

2.2.Period Period decreasesdecreases

3.3.Period remains Period remains the samethe same

Fastest Responders (in Fastest Responders (in seconds)seconds)

0 Participant 1

0 Participant 2

0 Participant 3

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Racing Leader BoardRacing Leader Board

Waves ultimately break when the top of the wave gets ahead of the bottom of the wave due to more friction at the bottom. The depth is usually 1.3 times the wave height = 1/7th of the wavelength

Spilling breaker – wide, flat

Plunging breaker – narrow, steep

Surging breaker – V. narrow, V. steep

The type of breakerformed is determinedby the steepness of the surf zone.

Mr. Salmore

Waves may notbreak, but insteadcan be reflectedoff near verticalsurfaces producingoutgoing waves.

Figure 9.17

• Wave refractionWave refraction refers to the bending of the wave crest as waves enter shallow water. It is due to differences in speed produced by differences in water depth.

Shallower area

Effects of wave refractionEffects of wave refraction

Wave Refraction

Wave Diffraction

SummarySummary

• Waves are disturbances that move Waves are disturbances that move along or beneath the sea surface.along or beneath the sea surface.

• The size of surface waves depends The size of surface waves depends on the speed and duration of the on the speed and duration of the wind, and the fetch.wind, and the fetch.

• Waves affect water to a depth Waves affect water to a depth equal to or less than one-half their equal to or less than one-half their wavelength.wavelength.

SummarySummary

• As waves enter shallow water their As waves enter shallow water their wavelength shortens and their height wavelength shortens and their height increases. increases.

• The most damaging effect of storms is The most damaging effect of storms is not necessarily the waves, but the not necessarily the waves, but the storm surge (elevated sea level) storm surge (elevated sea level) created by the winds which pile water created by the winds which pile water up along the shore.up along the shore.