Currents, Waves and Tides Flashcards
Name the order of the atmospheric cells from the north pole to the mid-latitudes.
Polar > Ferrel > Hadley.
What is the ‘Coriolis Effect’?
A projectile fired towards the north in the northern hemisphere has an apparent deflection to the right, and to the left when fired towards the south in the southern hemisphere.
Name the global wind patterns in order from the north pole to the south pole.
Polar high Subpolar low Westerlies Subtropical high Trades Equatorial low Trades Subtropical high Westerlies Subpolar low.
What are ocean gyres?
A large system of circulating ocean currents caused by the Coriolis effect.
What direction does the water circulate in an ocean gyre located in the northern hemisphere?
Clockwise.
What direction does the water circulate in an ocean gyre located in the southern hemisphere?
Anticlockwise.
What is an ‘Ekman’spiral’?
A structure of currents or winds near a horizontal boundary in which the flow direction rotates as one moves away from the boundary.
What is the equation used to calculate the celerity (C) of waves?
C = L / T
L = Wavelength T = Wave period.
Describe the motion of seawater.
- Water particles move in orbits
- It is the wave that progresses
- Orbital diameter diminishes with depth.
What factors do wave height depend on?
- Strength of wind
- Duration of wind
- ‘Fetch’.
What does wave speed in deep water depend on?
Wavelength or period.
Do waves travel faster if they are shorter or longer?
Longer.
What applies when D < L/20?
C = Square root of (gD).
How does energy vary with depth?
It doesn’t.
What breaking wave type is formed over a flat bottom?
Spilling breaker.
What breaking wave type is formed over a steep bottom?
Plunging breaker.
What breaking wave type is formed over a very steep bottom?
Surging breaker.
What is a semi-diurnal tide?
Where there are two high and two low waters in one day.
How long is a lunar day?
24 hours 50 mins.
What is the effect of the sun at new moon on tides?
- Tide generation forces of moon and sun act in same direction
- Higher high water
- Lower low water
- Greater tidal range - spring tide.
What is the effect of the sun at half moon on tides?
- Tide generating forces of moon and sun oppose each other
- Lower high water
- Higher low water
- Smaller tidal range - neap tide.
What is the effect of the sun at full moon on tides?
- Tide generating forces of sun and moon and act in same direction
- Higher high water
- Lower low water
- Greater tidal range - spring tide.(So two periods of spring tide per month.)
What is the effect of the sun at third quarter moon on tides?
- Tide generating forces of moon and sun oppose each other
- Lower high water
- Higher low water
- Smaller tidal range - neap tide (So two periods of neap tides per month.)
How long is the lunar month?
29.5 days.
