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Chapter 3:
Weather and
Climate
SECTION ONE: EARTH-SUN RELATIONSHIP
Climate and Weather

1. Weather is the condition of the
atmosphere in one place over a short
period of time.

2. Climate is the average weather
conditions averaged over many years.

3. The most important factor in
determining the climate of an area is
earth’s position in relation to the Sun.
Earth’s position in relation
to the sun.
Earth’s Tilt and Rotation
1. The earth’s axis is an imaginary line that runs
through the center of the earth between the North
and South Poles.
2. The earth is tilted on its axis at about 23 ½ °.
3. Because the earth is tilted on its axis, not all places
on earth receive the same amount of sunlight at the
same time.
4. The most common scale for measuring temperature
are Fahrenheit(°F) and Celcius (°C).
Earth’s Tilt
Earth’s Revolution
1. The earth rotates on its axis every 24 hours and revolves
around the sun every 365 ¼ days.
2. The Earth’s revolution and tilt affect the amount of
sunlight that reaches different locations on earth at
different times of the year.
3. When the North Pole is tilted towards the sun, it is
summer in the northern hemisphere. When the North
Pole is tilted away from the sun, it is winter in the
northern hemisphere.
Winter Solstice-Northern
Hemisphere
4.
The seasons are reversed north and south of the
equator. When it is summer in the northern hemisphere,
it will be Winter in the southern hemisphere. When it is
spring in the northern hemisphere, it is Fall in the
southern hemisphere.
5.
Twice a year (March 21 and September 23) the
direct sunlight falls on the equator. This day is called an
equinox, meaning “equal night,” because daytime and
nighttime hours are equal. Equal amounts of sunlight
reach the northern and southern hemispheres.
Equinox
6. On June 21, the sun’s direct rays strike the Tropic of Cancer
at 23 ½ ° North, bringing the longest day of the year in the
Northern Hemisphere. This day is called the summer solstice
and marks the beginning of the summer season in the
Northern Hemisphere.
7. On September 23, the suns most direct rays strike the equator,
marking the end of summer and the beginning of fall or
Autumn.
8. As the earth continues in its revolution, the direct rays of the
sun eventually strike the Tropic of Capricorn at 23 ½ ° South.
This brings the shortest day of the year and the beginning of the
winter solstice in the Northern Hemisphere.
Solstice and Equinox
9. For six months of the year, one pole will receive almost
24 hours of continuous sunlight each day while the other
pole receives almost no sunlight.
10. Continuous sunlight, a phenomenon known as
midnight sun is caused by the tilt of the earth’s axis as it
revolves around the sun.
Midnight Sun
Winter Solstice Antarctica
24 hours of darkness
The Greenhouse Effect
1.
The earth’s atmosphere reflects some of the suns
radiation back into space. Enough radiation reaches
earth’s surface to warm the air, land, and water.
2.
Once Earth’s surface absorbs this radiation from the
sun and is warmed, it then radiates this heat back into the
atmosphere.
3.
The earth’s atmosphere provides just about the right
amount of insulation to promote life on the planet.
4.
The 50% of the sun’s radiation that reaches the earth
is converted into infrared radiation, or heat.
5.
Clouds and greenhouse gases such as water vapor,
methane, and carbon dioxide absorb the heat energy and
trap it so that most of it cannot escape back into space.
6.
The atmosphere is like a greenhouse in that it traps
enough radiation to warm the land, water, and air and help
plants grow, while reflecting some radiation to ensure that
the earth does not overheat.
7.
This greenhouse effect is the warming of the earth
that occurs when sun’s radiation passes through the
atmosphere, is absorbed by the earth, and is radiated as heat
back into the atmosphere where it cannot escape back into
space.
8.
Without the greenhouse effect, Earth’s average
temperature would be below 0°F and life as we know it
would not exist.
9.
According to the laws of physics, what would
happen if the Earth gave back less energy than it received
from the sun?
10. What would happen if the Earth gave back more
heat energy than it received from the sun?
11. What would Earth be like if no greenhouse effect
existed in our atmosphere?
12. Which places on earth receive the most direct
sunlight? How does this affect their climates?
13.
What is the northernmost line of latitude to
receive the direct radiation from the sun?
14. What is the southernmost line of latitude to
receive the direct radiation from the sun?
Global Warming
15. Some scientist claim that rising carbon dioxide
levels in Earths atmosphere may be linked to rising
average global temperatures. This trend is known as
global warming and may be linked to human activities
such as the burning of fossil fuels, deforestation, and the
release of methane gas.
16.What are some possible future effects of global
warming?
17. What are some ways to reduce the human impact on
global warming?
Section 2:
Factors Affecting Climates
Climates are influenced by latitude, elevation, wind
and ocean currents, mountain ranges, and a places
location in relation to large bodies of water.
Latitude, Climate, and
Elevation:
Because of Earth’s revolution around the sun,
climates can be found in predictable patterns or
zones of latitude.
World Climate Patterns
Low Latitudes
The low latitude climate zone, also called the
tropics, is between 30°S and 30°N. This includes
the Tropics of Cancer and Capricorn and the
Equator. This area receives direct rays from the sun
and therefore have warm to hot climates.
Low Latitude ClimatesTropics
Low Latitudes-Tropics
High Latitudes
The high latitude zone includes Earth’s polar areas,
which are located between 60° to 90°N and 60° to
90°S. When either the Northern or Southern
Hemispheres are tilted towards the sun, its polar
areas receive continuous, but indirect sunlight.
These latitude zones are the coldest on earth.
High latitudes-Polar
Region
Mid Latitudes
The Mid latitude zones, between 30° to 60° North
and 30° to 60° South, have temperate climates
ranging from hot to cold. The mid-latitude climates
have the most dramatic seasonal weather changes.
Mid Latitude- Temperate
Elevation Affects Climates
Elevation, or height above sea level, has a major
influence on climates because of the relationship
between elevation and Temperature. As elevation
increases, the temperature will decrease. This is
because the earth’s atmosphere thins as altitude
increases. The less dense the air is, the less heat it
will retain. As elevation increases, temperatures
decreases by about 3.5°F for every 1000 feet.
As Elevation increases,
Temperature decreases.
Wind and Ocean Currents:
Air moving across the surface of the earth is called Wind.
Winds occur because sunlight heats the atmosphere and the
surface of the earth unevenly. Warm temperatures cause
the air to expand, become lighter, and rise into the
atmosphere creating areas of low pressure. Cool
temperatures cause air to sink in the atmosphere, creating
areas of high pressure.
Warm Air Rises
Prevailing Winds
Wind and Air Pressure
Air moves from areas of high pressure to areas of
low pressure, so the cooler air sinks to replace the
warmer rising air. These movements of air cause
winds to distribute the sun's energy, or heat around
the planet.
Air moves from High to
Low Pressure
Ocean currents
Ocean currents also help distribute energy around
the planet. These Ocean currents are usually cold or
warm streams of seawater that flow in a circular
pattern in the ocean. As they circulate, cold water
from polar areas moves slowly toward the Equator.
Warm water moves away from the equator into
cooler water.
Ocean Currents
Patterns of wind and
ocean currents:
As winds blow because of pressure differences on
Earth’s surface, warm tropical air moves toward the
poles and cool polar air moves toward the equator.
This movement of air creates the global winds that
blow in fairly constant patterns, called prevailing
winds.
The Coriolis Effect
The direction of prevailing winds is determined by
latitude and is also affected by the Earth’s movement.
As the Earth rotates from West to East, the paths of
the prevailing winds are bent to the right in the
northern hemisphere and to the left in the southern
hemisphere. This phenomenon is called the Coriolis
effect and causes winds to blow diagonally.
Trade Winds
Winds are generally named for the direction from
which they blow. The prevailing winds of the lowlatitudes were called Trade Winds because they
moved early trading ships. They blow from about
30° northeast and southwest towards the Equator.
Prevailing Winds
Westerlies and Polar
Easterlies
Westerlies are the prevailing winds in the midlatitudes. They blow from west to east between 30°
to 60° north and south of the equator.
In the high latitudes, Polar easterlies blow
diagonally from east to west, pushing cold air
towards the mid-latitudes.
Doldrums
Near the equator, warm air rises leaving a narrow,
generally windless band of calm air called the
Doldrums.
Doldrums and Horse
Latitudes
Horse Latitudes
Just north of the Tropic of Cancer and south of the Tropic of
Capricorn are two windless bands caused by high pressure
air sinking back to the earth. In the days of sailing ships,
these windless areas were feared by sailors because they
could become stranded without the prevailing winds to
power their ships. To lighten the load of ships caught in
these windless zones, sailors often had to lighten the load of
the ships by dumping cargo, such as livestock into the ocean.
The Horse Latitudes, the calm areas at the edge of the
tropics, derived their name from this practice.
Ocean currents and the
Coriolis Effect
Cold and warm ocean currents move in patterns in
the ocean similar to the patterns of wind movement.
Ocean currents are caused by many of the same
factors that cause winds including Earth’s rotation
air pressure, and differences in water temperature.
The Coriolis Effect also affects ocean currents.
Coriolis Effect
Warm and Cold Ocean
Currents
Cold ocean currents generally flow on the west
coast of continents and cool the coastal land areas.
Warm ocean currents generally flow on the East
coast of continents and bring warmer temperatures
and humidity to coastal areas they pass. A good
example of this is the North Atlantic Drift that
carries warm water to the west coast of Europe
creating a mild climate in spite of its northern
latitude.
Influences on Weather:
Water vapor forms in the atmosphere from
evaporated surface water. The high temperature
causes the air to rise. As the air rises, it cools,
condenses into clouds, and then releases water
droplets in the form of precipitation.
Temperature’s effect on
Precipitation
Warm air is able to hold more water vapor, so as
warm air rises and cools, it eventually will reach a
temperature in which the air is unable to hold it as a
vapor or clouds any longer. At this point the air is
saturated and gravity pulls the water droplets back to
Earth as precipitation.
El Nino
El Nino is a periodic change in the pattern of ocean
currents, water temperatures, and weather in the
mid-Pacific. El Nino does not occur every year, but
has increased in frequency since the 1970’s. In an El
Nino year, prevailing winds and ocean currents may
reverse direction, causing warm water to spread
along the coasts of Ecuador, Peru, and Chile.
El Nino’s Effects
These changes in the Pacific influence
climates around the world. Precipitation
increases along the coasts of North and South
America, making the winters warmer and
increasing the risk of Flooding. In Southeast
Asia and Australia, drought and forest fires
occur. Winter rains are heavier along the
west coast of North America.
El Nino Flooding in South
America
Landforms and Climate:
Large bodies of water are slower to heat and cool, so
they tend to keep temperatures in surrounding lands
moderate. Coastal lands often experience less
changeable weather as a result of this.
The interiors of continents tend to experience
extremes in seasonal temperatures.
Gobi Desert
Rain Shadow Effect
Mountain ranges affect climates. Increases in
elevation bring decreases in temperature. Mountain
ranges push wind upward. The rising air cools
releasing moisture in the form of Precipitation.
Most of the precipitation falls on the Windward side
of the mountain, or the side facing the wind.
Rain Shadow Desert
After the precipitation is released, winds become
warmer and dryer as they descend on the leeward
or opposite side of the mountain. The hot dry air
produces little precipitation in an effect known as
Rain Shadow Effect. The rain shadow often causes
dry areas, and even deserts to develop on the
leeward side of a mountain range.
Chapter 3, Section 3:
World Climate Patterns,
Climate Regions, and
Biomes
Climate Regions and Biomes
Climates are organized into five climate zones: tropical, dry
or (arid), mid-latitude or (temperate), high-latitude or
(polar) and highland (mountains).
Biomes, or ecosystems are defined by a specific community
of plants and animals that inhabit a region. Biomes are
classified into four main categories: forests, grasslands,
deserts, and tundra.
Earth’s Climate Zones
Earth’s Biomes
Biomes
Biomes are affected by climate and terrain, or
physical characteristics of the surface of the land.
The key influences of climate are temperature,
precipitation, and latitude.
Similarities in climates often result in similar biomes.
For example, areas that receive large amounts of
rain and have warm temperatures tend to have lush,
green rain forests. These areas tend to be located
near the equator.
Tropical Climates:
Tropical Climates are found in or near the low-latitudes in
areas referred to as the tropics.
Tropical Wet, or rain forest climates are warm, humid, and
rainy year-round. Annual rainfall averages from 50-260
inches. This much rain tends to strip the soil of nutrients.
The biome in these climates are the tropical rain forests,
characterized by thick vegetation that grows in layers. Tall
trees form a canopy over shorter trees and bushes, and
shade-loving bushes grow on the forest floor.
Rain Forest
Amazon Rain Forest
The world’s largest rain forest is in the Amazon River
Basin. Scientists estimate that more than half of all
the plant and animal species in the world are found
in tropical rain forests.
Tropical Wet/Dry Climates
Tropical Wet/Dry climates have very distinct wet
and dry seasons, with high year-round
temperatures. Typically, summer is the wet season
and winter is the dry season. These regions are
called savanna biomes and scattered trees and
grasslands are common vegetation. Large herds of
grazing animals may be found in the savanna
grasslands of Africa.
Tropical Savanna
Dry Climates:
The two main types of dry climates are semi-arid
(or steppe) and arid (or Desert).
Steppe climates are usually located away from
oceans or large bodies of water and are less-humid.
These areas average between 10-30 inches of
precipitation per year. Steppe grasslands have warm
summers and very cold winters. The steppe biome
has mainly dry grassland vegetation with very few
trees. The largest steppe grassland in the world
stretches from China and Mongolia in the East to
Europe in the West.
Steppe Grassland
Deserts
Deserts are extremely dry areas that receive about 10
inches of precipitation or less per year and support a
very small amount of plant and animal life. Only
plants that can live without much water and tolerate
extreme temperatures live in desert climates. Most
deserts are hot and dry, although some can be
extremely cold. Some deserts have underground
springs that support an oasis, or area of lush
vegetation.
Desert Biome
Deserts
Desert temperatures tend to vary widely from day
to night because of the lack of humidity (or
moisture) in the air. A band of deserts are
distributed around the world near 30° latitude
because this is where high pressure air sinks back to
the earth creating clear, stable weather. Deserts
may also be found on the west coast of continents
near cold ocean currents.
Distribution of Deserts
Mid-Latitude Climates (30°60°):
Humid subtropical
Humid Continental
Marine West Coast
Mediterranean.
Humid Subtropical
Humid subtropical climates have short, mild
winters, hot and humid summers and year-round
rain. The southeastern part of the U.S. experiences
this type of climate. Prevailing winds from the Gulf
of Mexico keep this region warm and humid.
Vegetation in this region consists of prairies and
mixed deciduous and coniferous forests. Coniferous
trees are evergreen and have cones. Deciduous
trees have broad leaves that change color and drop
from the trees in the fall.
Humid Subtropical
Deciduous Trees
Coniferous Trees
Marine West Coast
Marine West Coast climates can be found on the
Southern coast of Chile, Australia, the British Isles,
and the Pacific coast of North America. Ocean
winds bring cool summers and cool, rainy winters.
The abundance of rainfall supports both coniferous
and deciduous forests. Seattle, Washington
experiences this type of climate.
Marine West Coast
Mediterranean Climates
Mediterranean climates can be found surrounding
the Mediterranean Sea, central California, and the
Southwestern coast of Australia. These areas
experience mild, rainy winters and hot, dry summers.
The natural vegetation includes thickets of woody
bushes and short trees known as Mediterranean
shrub, or chaparral vegetation. Grapes, olives, and
citrus fruits are common crops grown in these
regions.
Mediterranean Biomes
Humid Continental Climates
Humid continental climates are found on the
eastern part of continents in the upper middlelatitudes. Winters can be severely cold the further
north the location and summers can be warm. This
climate experiences the most extreme change of
seasons and weather patterns. The natural
vegetation will be mixed deciduous and coniferous
forests. The most-northern parts of this region are
mostly coniferous forests.
Humid Continental Climates
Humid Continental Climate
High-Latitude Climates:
In the high-latitudes, freezing temperatures are
common all year because of the lack of direct
sunlight. As a result, the amount and variety of
vegetation is limited.
Subarctic Climates
Just south of the Arctic Circle are the subarctic
climate regions. Winters here are bitterly cold and
summers are short and cool. In parts of the
subarctic, only a thin layer of topsoil thaws, leaving
a permanently frozen subsoil called, permafrost.
Needle-leaf evergreen (or coniferous trees), may
be the dominant vegetation in this region.
Taiga, Boreal, Coniferous
Forest
Tundra Climates
Closer to the poles are the Tundra climate regions.
Winter darkness and bitter cold lasts for months.
While summer has only limited warming. The
permafrost prevents tree from growing here, so
vegetation is limited to low bushes, short grasses,
lichens, mosses, and some flowers.
Tundra Vegetation
Ice Cap Climates
Ice cap climates cover the poles. Snow and ice can
reach 2 miles thick and lichens may be the only
vegetation. Temperatures average below freezing
every month.
Ice Cap
Highland Climates
Highland, or mountain climates vary with elevation.
The lower elevation regions of mountains have
warmer climates and the higher elevations have
colder climates. Each climate zone is suitable for
different vegetation and animals.
Highland Climates
Extreme weather and
climates:
Hurricanes are westward moving tropical storms
caused by warm air rising from the warm waters
near the equator. High winds, flooding, and loss of
lives result from hurricanes. Most deaths are
caused by the storm surge. Hurricanes have
sustained wind speeds of at least 72 mph.
Monsoons
Monsoons are seasonal shifts in wind that cause
dry seasons in the winter and flooding in the
summer in large areas of South Asia (India) and
Southeast Asia.
Tornados
Tornados are violently rotating columns of air that
result from a large thunderstorms called a super
cell. There are more tornados in the area of the
United States called tornado alley, than any other
region of the world.
Drought
Droughts are long periods of low rainfall totals
resulting in desertification and loss of agriculture.
California is currently experiencing a severe
drought.