Transcript Document
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Waves
Wave Spectrum Surface waves deep-water waves shallow-water waves Wave Development Wave Equations Global Wave Heights
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Wave Spectrum
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Surface Waves
Deep -water Waves
D > L /2
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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
D < L /20
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
P Wave height depends on three factors: 1. Wind speed - how fast it blows 2. Wind duration - how long it blows 3. Fetch - the area over which the wind acts
08_07
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As wave speed increases, wavelength and wave period also increase.
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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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(D< L/ /20)
Know this one Know this one
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Global Wave Heights
P High in high latitudes, low in low latitudes
S Northern Hemisphere Winter, highest waves
S Southern Hemisphere Winter, highest waves
P Cause And Effect Wind Speed 10/92 Wave Wave Height
08_11
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Highest wave recorded at sea - 34 meters (112 feet)
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Waves
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 INTERFERENCE PATTERNS
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.
08_A
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A Stationary or Standing Wave
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
Yellow dashed line indicates undisturbed sea level. Dots indicate water motion.
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Binodal Standing Wave
Yellow dashed line indicates undisturbed sea level. Dots indicate water motion.
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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Internal Wave Propagation
Yellow dashed line indicates undisturbed sea level. Dots indicate water motion.
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Atmospheric Internal Waves
Rising air cools, water condenses clouds form. Sinking air warms and clouds evaporate.
S 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.
S 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.
S 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
Results from elevated sea levels pushed ahead from storms such as hurricanes.
If they come ashore at high tide, they can cause considerable damage.
The effects of storm surge on coastal areas.
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08_09
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