Transcript Air, Water, and Solar Energy

Air, Water, and Solar
Energy
Chapter 14
Key concepts
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How the earth’s spherical shape affects
temperature and wind patterns
Why the tilt of the Earth’s axis causes seasons
How Earth’s rotational motion affects wind
and water currents
How the continents influence ocean currents
How the continents and the oceans affect the
air above them.
Solar energy and a spherical earth
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The Earth is a spherical, rotating, orbiting planet.
These motions determine the amount of solar radiation
absorbed by different parts of the planet.
Latitude measures distances north or south of the equator in
degrees of the angle made with the centre of the earth and the
equator as the initial arm. The terminal arm is at the desired
location. See text p. 454
Longitude measures distances east or west from a reference
line called the prime meridian which runs from the North
Pole through Greenwich, England to the South Pole. It is also
measured in degrees with the centre of the earth as the vertex
and the line from the centre to the prime meridian as the
initial arm. The terminal arm is at the desired location.
Hot and Cold
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A beam of sunlight that strikes the earth at the
equator is perpendicular to the surface of the
planet. An identical beam striking at 45º N
latitude or 45º S latitude would be more
spread out than at the equator so the solar
energy would be distributed over a larger area.
Closer to the poles, the energy would be
spread out over an even greater area
Solar energy distribution on impact
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The Four Seasons
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According to Vivaldi…. 
Consider Earth’s orbit around the sun and
earth’s orientation in this orbit. See text p. 455
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Four Seasons
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Refer to text p. 456
Starting at the left, the tilt is toward Sun causing
summer in the Northern hemisphere.
As the earth moves counter clockwise, summer in
the Northern hemisphere changes to fall
At the right end of its orbit, the tilt is away from the
Sun and it is winter in the Northern hemisphere.
At the two midpoints of the orbit, the Sun’s rays are
perpendicular to the equator and equal amounts of
energy are received by the hemispheres. These are
the spring and autumn equinox.
The orbit takes roughly 365.25 days
Circles and Zones
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The Arctic and the Antarctic Circles define the polar
zones.
The Tropic of Cancer and the Tropic of Capricorn define
the tropical zone.
Between each circle and each tropic is the temperate
zone
Zones are characterized by their general climate i.e the
average weather conditions over many years
Polar zones receive 24 h of sunlight at times but this
does not impact global warming. Why?
Temperate zones usually have a big difference between
summer and winter since the sun’s rays are never
perpendicular there.
Worldwide Wind Currents
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Why do Weather Systems Generally Move
from West to East in Canada?
1. Uneven heating causes wind
2. Cool air flows toward and under warm air
3. Spherical shape of Earth causes uneven
heating i.e more at the equator than at the
poles.
Worldwide Wind Currents
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4. We’d expect air movements as shown on p.462, but the
Earth is not a small sphere, it is very large. Global
movements of air do not follow the simple pattern that land
and sea breezes do and this does not account for the rotational
effects of the Earth on wind patterns.
5. Warm air from the equator rises north or south and then
cools by the time it has reached about 30 N or S latitude.
6. Some of that air then moves back toward the equator and
some continues to move toward the poles but closer to the
Earth.
Worldwide Wind Currents
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7. Cold polar air flows from the poles toward the
equator but by the time it reaches 60 N or S latitude
it has warmed sufficiently to begin rising again.
8. This gives rise to three closed patterns of air
movement seen on p.463 fig 14.8B
9. Now we must account for the Earth’s rotation. The
earth moves at about 300 m/s or 1200 km/h . We
rotate along with the atmosphere but different places
on the Earth move at very different speeds. See p.
463 at the bottom.
Worldwide Wind Currents
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10. Air between 30N and 60N latitude i.e. most of
Canada and the U.S. is rising due to convection
currents toward the North Pole, and rotating west to
east along with the Earth. This combined effect
causes the air to move from west to east and are
called the prevailing westerlies. The effect of the
Earth’s rotation on air or any object moving of the
surface of the Earth is called the Coriolis Effect.
Jet Stream
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Was discovered by pilots in 1944 flying at altitude of
10 km. Discovered the plane was travelling at 700
km/h faster than its top speed of 600 km/h.
Jet streams are ribbons of extremely fast moving air
near the top of the troposphere and are caused by
contact between cold and warm air. They are found
at the boundaries of polar and temperate zones and
temperate and tropical zones.
The polar jet stream affects our weather
Jet Stream
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When prevailing westerlies are far enough north, they meet
the cooler polar easterlies. The cooler air pushes beneath the
warmer air and forces them up. As the air rises it encounters
fewer barriers such as mountains so it accelerates. When this
convection current combines with the Coriolis effect, the air
travels at speeds from 100 km/h to 300 km/h. Jet streams can
be thousands of km long and two or three hundred km thick.
They are not circular and curve and meander north and south.
Generally, the weather north of the stream is colder and south
of the stream , warmer. In winter, wind patterns shift south
along with the jet stream, and in the summer, the jet stream
retreats far north. Both of these are due to the uneven heating
pattern due to the Sun’s rays in summer and winter. See text
p. 467
Rivers in the Sea
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Surface ocean currents are primarily due to the
influence of surface winds. Some of these carry
warm water from the equator to the Arctic sea.
Others carry cooler polar waters toward the equator.
Although surface currents are started by wind, they
are blocked and diverted by the continents.
The Coriolis effect influences ocean currents as well
as winds. Notice that ocean currents turn to the right
in the Northern hemisphere and to the left in the
Southern hemisphere.
Rivers in the Sea
Rivers in the Sea
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Circular or elliptical currents are called gyres. They
circulate clockwise in the Northern hemisphere and
counter clockwise in the Southern hemisphere.
The right or eastern sides of the gyres have cool
currents and the left or western sides have warm
currents. Suggest a reason for this.
Cooler currents cool the air above them. Cool air
holds less water vapour so the land close to these
currents tend to be drier.
Warmer currents hold more water vapour so the land
close to them tends to have warmer air and more
precipitation
Rivers in the Sea
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There is no complete current circling the
Northern hemisphere because the continents
get in the way.
However, just north of Antarctica, the West
Wind Drift encircles the world. It brings cold
polar water and air to western parts of South
America, Africa, and Australia.
It is the largest surface current.
Rivers in the Sea
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Deep ocean water is not affected by winds,
however, there are slow moving currents in
this water. Ocean water also moves vertically.
Temperature and salinity affect ocean water.
Cooler water is more dense than warmer
water so it sinks below the warmer water.
Salt water denser than fresh water so it sinks
as well.
The Great Ocean Conveyer Belt
The Great Ocean Conveyer Belt
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The largest continuous ocean current
Really thermo-haline circulation. Meaning?
How does it work? See text p. 474
Start at Greenland
The Great Ocean Conveyer Belt
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Much of warm water
from Gulf Stream & N.
Atlantic Drift
evaporates leaving
behind saltier water.
When it reaches Arctic
O, it mixes with colder,
saltier water and sinks
to the bottom, heading
south to Antarctica
Great Ocean Conveyer Belt
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It turns east, splits into 2
branches-one heads to
Indian O the other
continues east. They join
other currents and
complete the circuit.
Transit time is about 1000
a.
Mechanism to transport
nutrients and thermal
energy from pole to pole.
El Niño
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Coastal upwellings arise when constant winds blow
from the shore to the sea. Nutrients are brought up
from the ocean bottom.
Peruvian fishers named the warming phenomenon
which arrived in December El Niño. It disrupted
their fishing every few years.
Arises from a reversal in the pattern of circulation of
the trade winds and the upper level winds bringing
warm water and rains to South America.
Consequences include rains, flooding, typhoons,
drought, fires etc
Over Land and Sea
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Despite convection currents and the Coriolis Effect,
large bodies of air can remain in almost the same
location over a period of time. The air then takes on
the characteristics of the land or water below i.e
temperature and humidity. The body of air is called
an air mass.
They are classified as continental or maritime
depending on where they form. They are also classed
as polar or tropical (temperature-based).
When these large masses begin to move or collide
we get weather.
Properties of Air Masses
Name
Symbol
Characteristics
Continental polar
cP
Cool and dry
Maritime polar
mP
Cool and moist
Continental
tropical
Maritime tropical
cT
Warm and dry
mT
Warm and moist
Thanks for your attention Doc!
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