Air, Water, and Solar EnergyChapter 14

Key concepts 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 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 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 impactmembers.aol.com/pakulda/emstyg2.htm

The Four Seasons According to Vivaldi…. Consider Earth’s orbit around the sun and

earth’s orientation in this orbit. See text p. 455

www.greatlandofalaska.com/reference/faq.html

Four Seasons 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 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 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 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 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 10. Air between 30N and 60N 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 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 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 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 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 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 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 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 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 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 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 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 MassesName Symbol Characteristics

Continental polar cP Cool and dry

Maritime polar mP Cool and moist

Continental tropical

cT Warm and dry

Maritime tropical mT Warm and moist

Thanks for your attention Doc!

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