Transcript Unit 5 notes

Air-Sea Interactions
& Ocean Circulation
Air-Sea interaction
I. Intro
A. The atmosphere and Ocean act as an
interdependent system.
1. Ocean currents are created largely by
wind patterns
2. Many weather patterns are caused by
the ocean.
3. Extreme weather (drought, excessive
precipitation) are related to periodic changes
in oceanic conditions (like El Nino)
4. Oceans and land absorb about 50% of solar
radiation (due to water’s high heat capacity
this energy is maintained for long periods of
time).
5. Atmosphere and clouds absorb about 25% of
solar radiation
B. Properties of the Atmosphere
1. composition – Air is mostly Nitrogen and
Oxygen
2. Temperature
a. Troposphere- from
earth’s surface to about
7 miles above.
i. All weather is
produced here
ii. There is a great
deal of atmospheric
mixing at this level.
High altitudes are
colder.
3. Density – Warm air is less dense than cold air
(warm air rises and cold air sinks).
i. A convection cell is caused by hot air rising
and cold sinking.
4. Water vapor content
a. Warm air can hold more water (clothes dry
faster in a dry, warm breeze).
i. increase in water vapor decreases air’s
density (humid air less dense than dry).
5. Pressure – at sea level air has 1.0
atmospheres of pressure.
i. the higher you go, the less air on top of you
= lower pressure.
ii. Column of cool, dense air (heavier) = high
pressure = air sinks. Column of warm, less
dense air = low pressure = air rises.
iii. Sinking air begins to warm (compression) and
rising cools (expansion).
6. Movement – Air ALWAYS moves from high
pressure to low pressure.
a. This is wind.
C (capitol C). How the Coriolis Effect, effects
moving objects.
1. An object set in motion will move in a
straight line unless acted upon by another
force.
2. The earth rotates towards the East.
a. If you stood on the N. Pole you would be
rotating counter-clockwise.
b. If you stood on the S. Pole you would be
rotating clockwise.
3. Moving objects (above the surface) in N.
hemisphere will appear to curve to the right
(from viewers perspective).
a. in S. hemisphere they will appear to curve
to the left.
b. this is the Coriolis Effect.
More Coriolis Effect.
4. Merry-go-round example.
D. Global Atmospheric Circulation Patterns.
1. Circulation cells – caused by convection as
the result of low pressure (near warmer
climates) and high pressure (near colder
climates.
a. Hadley cells are located between 0 and 30
degrees north and south of the equator.
1. Responsible for creating the Trade Winds,
the strongest winds on earth.
b. Ferrel Cells – Between 30 and 60 degrees N.
and S. of the equator.
i. The driving force is the Hadley cells and
Polar cells. Like interlocking gears.
ii. This is the Temperate Zone and is the
location of the Westerly Winds.
c. Polar Cells – located between 60 and 90
degrees from the equator.
2. Pressure
a. Cool, dense air column descending at 30
degrees is called Subtropical Highs.
i Similar descending air at the poles are
called Polar Highs.
ii. Conditions = dry and clear skies.
b. Subpolar Equatorial low – 60 degrees
i. Warm rising air – lots of water
ii. Conditions – Cloudy with lots of
precipitation.
3. Wind Belts – Most wind is created by the
lowermost portion of a circulation cell (ie.
Near the ground).
a. The major belts include Trade Winds,
Westerlies, and Polar Easterly winds. (see fig
6.10)
4. Boundaries – area between wind belts are
typically lacking in wind (look at your fig. 6.10)
a. They include the Doldrums (0°), Horse
Latitudes (30°) and Polar Fronts (60°).
E. Weather and Climate Patterns of the ocean.
1. Winds – As air moves from high pressure to
low pressure, the coriolis effect modifies it.
a. In N. Hem, air moving away from High
Pressure moves away to the right
(Anticyclonic flow)
b. Air moving toward Low pressure moves in and
to the right.
i. flow around low pressure system called
Cyclonic Flow.
c. Sea breeze- land heats up and cools down 5
times faster than ocean (lower heat capacity).
i. Why does a sea breeze blow in to land at day
and out to sea at night? You tell me.
2. Storms and fronts – Conditions near equator
and poles fairly consistent and calm.
a. Storms (strong winds, precipitation, thunder and
lightning) common between 30° and 60°
(temperate zone where we are).
b. Storms are atmospheric disturbances caused
by air masses meeting.
3. Tropical Cyclones – AKA hurricanes, typhoons
and cyclones.
a. Caused by a low pressure cell moving away
from the equator, picking up energy as it
moves.
b. Hurricanes are an efficient way to redistribute
heat from one area to another.
F. Random Fact to memorize- When sea ice
forms the remaining seawater becomes more
salty….ie. More dense (remember cold seeps).
The End of Air-sea interactions.
Ocean Circulation
I. Intro –
A. Ocean Currents are masses of Ocean
Water in motion.
II. Forces driving ocean circulation.
A. Wind is the primary force driving ocean
surface circulation.
B. The Coriolis effect modifies this movement.
C. Near Equator – Trade winds drive currents
D. Temperate current (30 -60 degrees) –
Westerlies affect currents.
E. Polar currents affected by Polar Easterlies
F. Thermohaline circulation.
1. caused by water density (rising &
sinking)
2. Cold water is denser than warm water.
3. Saltly water (higher salinity) is more dense
than fresh or less-salty water.
4. Causes the Gulf stream to dive to the bottom
of the Atlantic near Greenland (cold and Salty)
G. Ekman spiral- Caused by
wind that has been
modified by the coriolis
effect.
1. Wind moving surface water in spiral
physically moves deeper water in similar
motion.
a. Sort of like a water hurricane, but totally
different ;-)
2. So as one moves down the direction changes.
a. at 100m the water flows at about 90
degrees to surface wind.
H. Upwelling- Deep nutrient-rich water from
ocean floor pulled to the surface at coastlines.
1. Caused by Wind, Coriolis Effect and Ekman
Transport.
I. Random Fact – During winter months in the
Indian ocean, dry monsoon wind blows
consistently from inland out to sea……Why?
1. Did you know Monsoons had a dry phase?
End of Ocean Currents
Weather documentary
Waves (3hrs)
I. Waves (surf) – moving energy traveling along
the interface of ocean and atmosphere.
•Wave stuff, or
stuff that waves
do.
A. The highest parts of waves are called Crests,
and the lowest are troughs.
B. The time between two successive waves is
called the Period.
B. Water waves are Orbital.
C. Wave Speed is equal to wavelength divided
(length) by period time. Eg. 20 m in 10 sec =
2.0 m/s while 25 m in 10 sec = 2.5 m/s
D. Deep vs. Shallow waves.
1. Shallow waves include tsunamis, tides and
near-shore wind generated waves.
a. speed of shallow wave is proportional to
water depth (the ocean floor begins to
slow it.
2. The speed of Deep water wave is proportional
to wave period
E. Wave height depends on Wind speed, Wind
duration and fetch (distance wind blows in a
single direction).
F. Rogue waves tend to occur where storm
waves move against strong currents.
1. large, spontaneous and dangerous to even
very large ships.
G. Typical order of wave formation – 1. Sea, 2.
swell, 3. surf.
1. Wind blows across the Sea, pushing
Swells, that break into Surf near the shore.
H. Waves that are breaking along the shore and
are forming in a curling crest over an air
pocket are called Plunging waves. (into the
mind)
I. Tsunamis are created by earthquakes on the
sea floor (particularly on convergent plate
boundaries)
Waves for Electricity
• The Majority of earth’s captured energy is in
the oceans.
• Waves are an ultimate result of energy
transfer from sun to ocean, to atmosphere
and back to the ocean again.
• We can harvest this energy.
• !00% renewable and Carbon neutral.
End of Waves