Waves

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Waves
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• Wave Spectrum
• Surface waves
• deep-water waves
• shallow-water waves
• Wave Development
• Wave Equations
• Global Wave Heights

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Deep Water, Progressive Wave
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Wave Spectrum
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• Where is the majority of wave
• energy in the ocean

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Tides
Gravity Waves
Different Types of Surface Waves
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Wave Generating Forces
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Wave Restoring Forces
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Surface Waves
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Deep -water Waves

• D gt L /2

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Deep Water, Progressive Wave
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08_06a
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Movement of water parcels is circular and the
orbit gets smaller with depth until there is no
motion at L/2.
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Shallow-water Waves
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• D lt L /20

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08_06b
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Movement of water parcels is elliptical and the
orbit gets flatter until it is just a back and
forth movement at the bottom.
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Wave Development
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Wave height depends on three factors

• Wind speed - how fast it blows
• Wind duration - how long it blows
• 3. Fetch - the area over which the wind acts

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08_07
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As wave speed increases, wavelength and wave
period also increase.
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S
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With a constant wind speed, wave height, length,
period and speed all increase as the fetch
increases.
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Wind speed, fetch and wind duration are usually
positively correlated as they increase, wave
characteristics increase.
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Wave Equations
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PP
Know this one
(Dlt L/ /20)
Know this one
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Global Wave Heights
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October 1992 TOPEX/Poseidon satellite
October 1992 TOPEX/Poseidon satellite
High in high latitudes, low in low latitudes
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Northern Hemisphere Winter, highest waves
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Southern Hemisphere Winter, highest waves
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Wind Speed 10/92
Cause And Effect
Wind Speed 10/92
Wave Height
Wave Height
Wave Height
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08_11
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Highest wave recorded at sea - 34 meters (112
feet)
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Waves
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• Wave Spectrum
• Surface waves
• deep-water waves
• shallow-water waves
• Wave Development
• Wave Equations
• Global Wave Heights

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Shallow water waves stack up as they approach
shore causing the wavelength to become shorter
and the height to increase.
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WAVE INTERFERENCEPATTERNS
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08_14
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Two wave trains can produce either larger or
smaller waves after interacting with each other.
Constructive interference can be the cause of
rogue waves that occasionally sink ships in the
absence of a severe storm.
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08_A
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A Stationary or Standing Wave
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Water flows back and forth about a node, a point
with no vertical water motion. The endpoints are
antinodes, points with maximum vertical water
motion.
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Uninodal Standing Wave
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Yellow dashed line indicates undisturbed sea
level. Dots indicate water motion.
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Binodal Standing Wave
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Yellow dashed line indicates undisturbed sea
level. Dots indicate water motion.
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THERE WILL BE A SEPARATE POWER POINT ON TSUNAMIS
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INTERNAL WAVES
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Internal waves occur along density boundaries,
i.e. a thermocline - the smaller the density
difference, the larger the waves that can be
produced.
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Slicks form at the surface above the troughs
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Internal Wave Propagation
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Yellow dashed line indicates undisturbed sea
level. Dots indicate water motion.
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Atmospheric Internal Waves
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Rising air cools, water condenses clouds form.
Sinking air warms and clouds evaporate.
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Eighty Mile Beach, north coast of Australia. High
altitude oblique photograph from the Space
Shuttle (November 1990). Shows reflections of
internal (not surface) wave forms progressing
toward shore. The distance between wave crests
is approximately 4.5 km.
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Gulf of Aden and Horn of Africa, Somalia. High
altitude oblique photograph from the Space
Shuttle (September-October 1988). Internal
waves are visible below the Gulf of Aden water
surface off Somalia. Waves show refraction
patterns produced by interaction with local
seafloor topography, including submarine canyons
that focus the waves near the center of the
photograph.
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Strait of Gibraltar, Gibraltar, southern Spain,
northern Morocco. High altitude oblique
photograph from the Space Shuttle (October 1984).
A spectacular set of internal waves are visible
where surface waters pass from the Atlantic Ocean
into the Mediterranean over deeper, denser waters
exiting the Mediterranean. These
large wavelength internal waves are visible here
in sunglint off the thermocline despite the lack
of any expression at the ocean surface.
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STORM SURGE
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• Results from elevated sea levels pushed ahead
  from storms such as hurricanes.
• If they come ashore at high tide, they can cause
  considerable damage.

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The effects of storm surge on coastal areas.
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08_09
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Storm surge from a hurricane
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Path of Super Storm Sandy