Waves and things. Homework Due Tuesday Read Pages 52-55. Answer in complete sentences What causes...
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Transcript of Waves and things. Homework Due Tuesday Read Pages 52-55. Answer in complete sentences What causes...
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
0 Participant 5
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
0 Participant 4
0 Participant 5
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.