Lecture 6 Flashcards
What is the angular velocity at a given latitude
-it is equal to the angular velocty times the square of the distance to the axis of its rotation
Does angular velocity increases if one moves northward in the northern hemisphere
- yes
- > if one moves northward in the northern hemisphere, one is decreasing the distance to the pole
- > thus to conserve angular momentum. the angular velocity must increase
- > to increase the angular velocty, eastward acceleration must occur
- > thus the deflection is to the east
What are waves
- waves are energy in motion
- > energy is being transmitted through cyclic motion in matter
- > the medium does not travel as the enrgy passes through
- > but particles oscillate in place as the energy passes through them
Do all waves begin as disturbances
-yes
What is a disturbing force
- it is the energy that causes ocean waves to form
- > eg; a rock thrown into a still pond creates waves that radiate out in all directions
-the most common is wind blowing across the ocean surface
What are the four ways that waves are created in the ocean
1) Interactions of winds with the ocean surface
2) Impacts on the ocean
3) Tidal interactions
- >caused by the gravitational pull of the Moon and the Sun
4)Passage of vessel or mairine mammals
What are the three different types of waves created with different densities
Air-ocean interface
- > movement of air across the ocean surface creates ocean waves(waves)
- > movement of air across creates atmospheric waves
- > movement of water across water creates internal waves
Where do surface and internal waves occur
Surface waves
->they only occur in the uppermost part of the ocean
Internal waves
->occur within the ocean along the boundary between water masses of different densities
Where are the largest waves in the world
-they are in the prevailing westerly wind belt in the Southern Hemisphere
Does the ocean’s tropical regions have small wave heights
-yes
What are internal waves associated with
- they are associated with a pycnocline
- > a pycnocline is a layer of rapidly changing density
- note internal waves are larger than surface waves
- > with heights exceeding 100 metres
What are the three different ways that particles can move due to energy transmission by waves
1) Longitudinal
- >back and forth
- >move through all states
2) Up and down
- >transverse
- >only move through solids
3) Around and around
- >orbital
- >a combination of transverse and longitudinal
- >aka interface waves
Do waves move matter in 3 dimensions
-yes
What are progressive waves
- they are those where the waveform can be observed travelling through the medium
- > eg; longitidunal, transverse and orbital waves are all progressive waves
What are the two competing forces that produce waves
Disturbing force
- > modified un-disturbed medium to create the wave
- > most common such force is the wind that blows over the surface and transfers energy to the ocean
Restoring force
- > this force tends to bring a system to its undisturbed state
- > for waves along liquid surfaces, the restoring force is gravity
What is a crest and trough
Crest
->the point of highest elevation of a wave
Trough
->between each pair of crests
What is a wave height, amplitude and wavelength
Wave height
->the vertical distance between the crest and the trough
Amplitude
->vertical distance between the crest or trough and mean water level
Wavelength
->the distance between each successive pair of crests or troughs
What is the definition of a wave period and frequency
Period
->time for the wave to move a distance equal to one wavelength
Frequency
->the number of crests or troughs that pass a fixed point per unit of time
What is the formula for the wave speed
- it is wavelength over the period
- > this is the rate the wave form moves at
- > not the water
What is the formula for wave steepness
- ratio of wave height to the wavelength
- 1/7 ratio dictates the maximum height of a wave
- > a wave 7 metres long can only be 1 meter high
- > any higher and it would break
Describe the circular orbit motion
- wave particles move in a circle
- > waveform travels forward
- > wave energy advances
- > individual particles that transmit the wave return essentially to the same place
- the object moves up and backward as the crest approach
- > the objects moves up and forward after the crest
- > down and forward after the crest
-the object moves down and backwards as the trough approaches
What is the wave base
- depth below the surface at which the circular orbit becomes so small
- > that the movement is negligible
- > equal to half of the wavelength measured from the still water level at the top
-so the circular orbital motion decreases quickly below the surface
What is a deep water wave
- if water depth is greater than wave base
- > wave is a deep water wave
-note deep-water waves have no interference with the ocean bottom
What does deep water wave speed vary with
- it only varies with wavelength
- > the longer the wavelength, the faster the deep-water wave travels
- a fast wave doesn’t necessarily have a large wave height
- > because wave speed only depends on wavelength
What are shallow-water waves
- if water depth is less than 1/20 of the wavelength
- > wave is a shallow ater wave or long wave
- shallow water waves are said to touch the bottom or feel the bottom
- > because they touch the ocean floor
- > which interferes with the wave’s orbital motion
Does shallow-water waves include all wind-generated waves
- yes
- >it includes all wind-generated waves in the open ocean where water depths far exceed the wavebase
Is shallow water wave speed determined by water depth
- yes and only water depth
- > so for shallow water waves, the deeper the water
- > the faster the wave travels
Describe how waves are created
- first waves to form are capillary waves(ripples)
- > they are small rounded waves with V-shaped troughs and small(1.74 cm) wavelengths
- over time, water catched more wind
- > more energy is transferred to the ocean and gravity waves develop
- > symmetric waves with wavelengths greater than 1.74 cm
- > initially gravity wavees are longer than they are high
