World Geography Semester 1
Unit 1 – North America
Climate
Weather
The condition of the atmosphere at a given place and time Ex: It is 95 degrees and sunny
in Plano, TX at 5:15 on June 28.
Climate
Average weather and weather conditions (precipitation and temperatures) averaged over
a long period of time; includes rare events (hurricanes) and long term global changes. Ex:
The summers are usually very hot in Plano, TX.
Air Pressure
The force exerted by air. The pressure causes wind and ocean currents. Unequal heating
of the earth causes pressure differences=wind. Wind always flows from high to low
pressure areas.
Wind Belts
The planet’s prevailing winds usually blow from the same direction causing predictable
patterns. These upper level winds are also known as jet streams. In the US, the Westerlies
cause most weather fronts to move from west to east across the country.
Equator – Doldrums; Tropics – Trade Winds; Mid-Latitudes – Westerlies;
Poles – Polar Winds
Rotation
Earth spins on its axis once every 24 hours and solar energy fuels the Earth and is
regulated by the rotation. Solar energy strikes the side of the Earth facing the sun and
creates day and night.
Revolution
The earth’s revolution is one year which is equal to one elliptical orbit every 365 and 1/4
days. The 1/4 is accounted for by a leap year once every four years – leap years happen
in the same year as the Olympics and US presidential elections.
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Tilt
Earth’s Tilt: The North polar axis of the Earth always points to the North Star and is tilted
at 23 and 1/2 degrees from perpendicular. The length of the day changes as we rotate
because of the tilt. Ex: Summer days are the longest – this happens in June in the
Northern Hemisphere and in December in the Southern Hemisphere. New Year’s is a
summer holiday in Australia. When the poles are next to rather than pointing at the sun,
we all have the same amount of sun. This happens in March and September and is called
the equinox. When the North Pole points toward the sun in June, it has constant daylight
and the South Pole has constant darkness. These are the solstices.
http://en.wikipedia.org/wiki/Image:North_season.jpg
The Tropics 0-30 degrees latitude (also known as the low latitudes)
The tropics are areas near the equator that receive the most constant sun because they
protrude outward. The Tropics are warm, low-latitude areas from 0 to 30 degrees. The
temperature averages around 80 degrees year-round. The climate type is usually tropical
wet – the rainforests. The direct rays hitting the equator are stronger because they are
concentrated on a small area.
Tropic of Cancer: Northern Hemisphere at 23.5 degrees N. When the sun’s rays are
directly on Cancer, it is summer in the north and winter in the south.
Tropic of Capricorn: Southern Hemisphere at 23.5 degrees S. When the sun’s rays are
directly on Capricorn, it is winter in the north and summer in the south.
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The Polar Regions 60-90 degrees latitude (also known as the high latitudes)
High latitude areas, very cold and marked by the North and South Poles at 90 degrees.
The higher the latitude, the lower the temperature. The poles have extreme differences in
daylight during the solstices when they are pointing either toward or away from the sun.
Their temperatures do not vary as much because they never get direct heat, just light.
The Middle Latitudes (located between 30-60 degrees latitude)
Temperatures can vary dramatically between hot and cold depending on the amount of
solar energy (or time of year). With four distinct seasons, these areas have the most
variation in climate because they have variations in light and heat. Most of the US falls in
the Middle Latitudes except Alaska, which is polar, and Hawaii which is tropical.
Solar Energy and the Seasons
The North and South Hemispheres have opposite seasons on the same dates. However,
there is little temperature change for people at the equator throughout the year. The
longer and warmer days are in the summer, but for the Southern Hemisphere this
happens in December and January.
Solstices
June 21
This is the date that the Northern Hemisphere has the longest day of the year, and this is
the first day of summer. The sun’s rays are most direct at the Tropic of Cancer. The
North Pole and the Arctic Circle – north of 66.5 degrees – have 24 hours of sun. The
southern hemisphere has the shortest day of the year, and this is the first day of winter.
The South Pole has a 24-hour night– the Antarctic Circle has 24 hours of darkness.
December 21
This is the date that the northern hemisphere has the shortest day of the year, and this is
the first day of winter. The North Pole has a 24-hour night. The southern hemisphere
has the longest day of the year, and this is the first day of summer. The South Pole has a
24-hour day – the Antarctic Circle has 24 hours of sunlight.
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http://upload.wikimedia.org/wikipedia/commons/4/4d/Earth-lighting-winter-solstice_EN.png
Equinox
Equinox means “equal night.” This occurs twice a year when the poles are not pointed
toward or away from the sun and the entire earth has 12 hours of sun. March 21 is spring
in the northern hemisphere and fall in the southern hemisphere. September 22 is fall in
the northern hemisphere and spring in the southern hemisphere. The days between
solstices and equinoxes get gradually shorter or longer. This creates seasons. The midlatitudes are most affected and have four distinct seasons.
http://upload.wikimedia.org/wikipedia/commons/8/84/Earth-lighting-equinox_EN.png
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Using the skills you learned in this lesson or any other resources, answer the following
questions. After you have answered these questions, go on to the second part of this
lesson.
True or False? If a statement is false, consider what part of it you could change
to make it true.
1. The revolution of the earth around the sun and the tilt of the earth’s axis cause the
changing of the seasons.
True
2. On March 21, every place has 12 hours of day and night.
3. On June 21, the Southern Hemisphere receives the maximum sunlight for the year.
4. On December 21, every place has 12 hours of day and night.
5. The Northern Hemisphere is pointed toward the sun on June 21.
6. On December 22, winter is beginning in the Northern Hemisphere.
7. On March 21, spring starts in the Northern Hemisphere and fall starts in the Southern
Hemisphere.
8. The Southern Hemisphere is pointed away from the sun on December 22.
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9. On December 22, the sun hits the hemispheres evenly.
10. Every 6 months, the sun has completed half of its revolution.
11. The sun’s rotation on its axis causes the seasons.
12. The imaginary line that runs through the center of the planet from pole to pole is
called the axis.
13. As the earth rotates, the side that faces the sun has night.
14. Land and water near the earth’s equator never have constant sun.
15. If rotation did not occur, one side of the planet would always be dark.
Some suggested sites for research include:
CIA World Factbook 2002 http://www.cia.gov/cia/publications/factbook/index.html
Encyclopaedia Britannica
Infoplease.com
http://www.britannica.com/
http://www.infoplease.com
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Six Factors That Affect Climate
Six basic factors of climate determine the amount of precipitation and the range of
temperatures for different locations on the earth. After learning these factors, you can
accurately predict on a map what the climate will be like in any location.
Latitude
Latitude is a measure of how far from the equator a location is. In general, the farther
from the equator, the colder it is. Latitude also affects what seasons a location will
experience. Locations in the Low Latitudes (between 0° to 30°) are hot year round and
usually have two seasons – wet and dry. Locations in the Middle Latitudes (between
30° to 60°) have four seasons – spring, summer, fall and winter. Although it is cold
year round, locations in the High Latitudes (between 60° to 90°) are cold in the
summer and very cold in the winter.
Continentality
The more towards the interior of a continent, the more extreme the temperatures will
be. A location with high continentality in the middle latitude region will have very hot
summers and very cold winters. This explains why the coldest temperatures on earth
(outside the Polar Regions) have been recorded in the northern interior of the Asian
continent. Water warms up and cools down more slowly than air, and therefore a
location closer to the coast has a climate that is more moderate, both cooler in the
summer and warmer in the winter.
Elevation
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The higher the elevation of a location, the colder and dryer it is. Two people at the
same latitude can have very different climates if one is close to sea level and the other
is on top of a mountain.
A topographical map (see example at right) is the main type of map used to depict
elevation, often through use of contour lines.
In a Geographic Information System (GIS), digital elevation models (DEM) are used to
represent the surface (topography) of a place, through a grid of elevations. You will be
using the National Atlas from the USGS – United States Geological Survey to create your
own GIS map.
Ocean Currents
The wind patterns blowing across the surface of the ocean combined with the position
of the continental landmasses create our planet’s ocean currents. Our currents follow a
general pattern of clockwise in the northern hemisphere and counterclockwise in the
southern hemisphere as shown on the map. The currents move cool water to warm
areas and vice versa. The planet is always trying to balance itself. For example, San
Francisco has a cool current and therefore cooler temperatures while Europe has a
warm current, the North Atlantic Drift, and therefore warmer than climates located
along the same latitude.
http://en.wikipedia.org/wiki/Image:Ocean_surface_currents.jpg
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Orographic Effect
The topography (landforms) of a continent can affect the precipitation of locations. The
windward side (usually ocean side) of mountain ranges will get much more rainfall than
the leeward side of mountain ranges. As the prevailing winds blow up the windward side
of a mountain, they get colder.
Colder air cannot hold as much water, so it is released as rain. By the time the air has
moved over the mountain tops, it has released most or all of its moisture so no rain
occurs on the leeward side. The dryness on the leeward side mountains is referred to as
the rain shadow effect.
For this reason, if there is a coast with a mountain range, the interior or leeward side of
the mountain will likely be a desert. The windward side is shown in the diagram below
on the left of the mountain peak and the leeward side is found on the right of the
mountain peak.
http://en.wikipedia.org/wiki/Image:Rainshadow_copy.jpg
Wind Systems (Prevailing Winds)
Because of the rotation of the earth and the friction between the planet and the
atmosphere, the directions the winds blow on our planet have a pattern to them. These
patterns are referred to as the prevailing winds. Winds that blow from east to west are
called easterlies. Winds that blow from west to east are called westerlies. These two
types alternate.
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http://en.wikipedia.org/wiki/Image:Earth_Global_Circulation.jpg
Using the skills you learned in this lesson or any other resources, answer the following
questions. When you have found the correct answers to these questions, use your
answers to help you take the quiz. The quiz will consist of ten questions taken from
both parts of this lesson.
Some suggested sites for research include:
CIA World Factbook 2002 http://www.cia.gov/cia/publications/factbook/index.html
Encyclopaedia Britannica
Infoplease.com
http://www.britannica.com/
http://www.infoplease.com
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Matching – Letters may be used more than once, only once or not at all.
1. Which side of a mountain range gets the most rain?
2. What redistributes ocean temperatures?
3. What is the most significant factor of climate?
4. Which effect explains the cause of deserts on the far side of mountains?
5. Which factor below does NOT impact climate?
6. Which factor leads to the cooling air that causes the orographic effect?
7. Which factor explains why Paris, France, is much milder then Fargo, North Dakota,
even though they have the same latitude?
8. Which factor includes the influence of westerlies?
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9. Which side of the mountain experiences the rain shadow effect?
10. Which factor would most impact Denver, the “Mile High” city?
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
Leeward
Windward
orographic
rain shadow
ocean currents
wind systems
continentality
elevation
latitude
longitude
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