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Meteorology
Characteristics of the
Atmosphere
Terms: atmosphere, air pressure,
troposphere, stratosphere, mesosphere,
thermosphere
Characteristics of the Atmosphere
• Describe the
composition of Earth’s
atmosphere.
• What does the name
of each atmospheric
layer mean?
• Why doesn’t the
thermosphere feel
hot?
The Composition of the Atmosphere
• The atmosphere is a mixture of gases that surrounds Earth.
• Makes conditions on Earth suitable for living things
• Gases keep the atmosphere on Earth’s surface warm enough
for water to exist as a liquid, protects against dangerous
radiation, prevents Earth’s surface from being hit by most
meteoroids or chunks of rock from outer space.
• Gases
– Nitrogen 78%
– Oxygen 21%
– Other gases 1%
– Water vapor <1%
• Solids
– Dust, volcanic ash, salt, dirt, smoke
• Liquids
– water
Atmospheric Pressure and
Temperature
• As altitude increases, air pressure decreases
– Air pressure is strongest at Earth’s surface
because more air is above you.
• Atmospheric composition affects air temperature
– Temperature differences result from the way
solar energy is absorbed as it moves through
the atmosphere
– High % of gases that absorb solar energy=
warmer
– Less gases that absorb solar energy = cooler
Layers of the Atmosphere
• Based on temperature changes:
– Troposphere: layer in which we live; contains almost
all of the weather, carbon dioxide, water vapor,
clouds, air pollution, and life-forms
– Stratosphere: gases are layered and don’t mix;
contains the ozone layer; protects life by absorbing
harmful UV radiation
– Mesosphere: middle layer; the coldest layer; most
meteoroids burn up here, producing meteoroid trails
– Thermosphere: temperature increases; does not feel
hot; outer most part of atmosphere; no definite outer
limit
Summary
• Nitrogen and oxygen make up most of Earth’s
atmosphere.
• Air pressure decreases as altitude increases.
• The composition of atmospheric layers affects
their temperature.
• The troposphere is the lowest atmospheric layer.
It is the layer in which we live.
• The stratosphere contains the ozone layer,
which protects us from harmful radiation.
• The mesosphere is the coldest atmospheric
layer. Meteoroids burn up in this layer.
• The thermosphere is the uppermost layer of the
atmosphere.
#1 Quick Check
•
Why does the temperature of different
layers of the atmosphere vary?
A. Because air temperature increases as
altitude increases
B. Because the amount of energy radiated
from the sun varies
C. Because of interference by humans
D. Because of the composition of gases in
each layer
#2 Quick Check
What is the most abundant gas in the
atmosphere?
a.
b.
c.
d.
oxygen
hydrogen
nitrogen
carbon dioxide
#3 Quick Check
A major source of oxygen for the earth’s
atmosphere is
a. sea water.
b. the sun.
c. animals
d. plants
#4 Quick Check
The bottom layer of the atmosphere where
almost all weather occurs, is the
a.
b.
c.
d.
stratosphere
troposphere
thermosphere
mesosphere
#5 Quick Check
The ozone layer is located in the
a.
b.
c.
d.
stratosphere
troposphere
thermosphere
mesosphere
Heat and Weather Patterns
• Weather
• visible light
climate
air masses
• sea breeze Convection currents
• Density
land breeze
Heat and Weather Patterns
• What is weather?
• What is climate?
• What is a sea
breeze?
• What is a land
breeze?
• What are air masses?
Heat and Weather Patterns
Weather and Climate
• Weather is the process in the atmosphere
that changes over a short period of time.
• Climate is the weather that is in place
most of the time or over a long period of
time.
• Is it Climate or Weather?
– What’s the weather like most of the time
where you live?
The Sun’s Energy
• Nearly all the energy in Earth’s
atmosphere comes from the sun.
• Most of the energy from the sun reaches
Earth in the form of visible light and
infrared radiation, with a small amount of
ultraviolet radiation.
• Visible light is energy you can see.
The Sun’s Energy
• Earth changes infrared radiation into
heat energy.
• Ultraviolet radiation causes sunburns,
skin cancer, and eye damage.
• Some of the sun’s energy reaches Earth’s
surface and is reflected back into the
atmosphere.
• Some of the energy is absorbed by the
land and water and changed into heat.
The Sun’s Energy
• Land heats up and cools down faster
than water.
• Water heats up more slowly than land
does, but holds the heat longer.
• Air heats up unevenly.
• Warm air becomes less dense and rises.
• Cooler air becomes more dense and
sinks.
The Sun’s Energy
• Wind that blows from an ocean or lake onto
land is known as a sea breeze.
• The flow of air from land to a body of water is
called a land breeze.
• Convection currents transfer heat from one
place to another through a liquid or a gas.
• In Earth’s atmosphere, convection currents
carry warm air upwards and cool air
downwards.
• This is because of the uneven heating of
Earth’s surface.
The Sun’s Energy
• Huge chunks of warm and cold air are
called air masses.
• Air masses move sideways across
continents and oceans.
• Clouds and storms form when these
masses run into each other.
• When a cold air mass meets a warm air
mass, thunderstorms may appear.
Quick Check
Land absorbs radiation from the sun
•
•
•
•
A. slower than water.
B. faster than water.
C. at the same rate as water.
D. almost never.
Quick Check
In the atmosphere, what happens in a
convection current?
•
•
•
•
A. cool air and warmer air both rise
B. cool air and warmer air both fall
C. cool air rises and warmer air falls
D. cool air falls and warmer air rises
Quick Check
What does solar (infrared) radiation produce
on Earth?
•
•
•
•
A. light
B. heat
C. land
D. water
Quick Check
In which direction does a sea breeze move?
•
•
•
•
A. toward the land
B. toward the sea
C. up
D. down
Quick Check
How are climate and weather alike?
• A. They both occur over short periods of
time.
• B. They both occur over long periods of
time.
• C. They both are affected by radiation
from the sun.
• D. They are both caused by even heating
of Earth’s surface.
What are Air Masses and Fronts?
(Chapter 16 Section 2)
• Terms: air mass, front, cyclone,
anticyclone,
What are air masses and fronts?
P. 490
• What are the major air
masses that influence the
weather in the U.S.?
• What is one source
region of a maritime polar
air mass?
• What are the
characteristics of an air
mass whose two-letter
symbol is cP?
• What are the four major
types of fronts?
Air Masses
• Air masses are large bodies of air where
temperature and moisture content are
constant throughout.
• Moisture content and temperature of a
mass are determined by the area over
which the air mass forms.
• These areas are called source regions.
Types of Air Masses
• maritime (m) – forms over water; wet
• Continental (c) – forms over land; dry
• Polar (P) – forms over the polar regions;
cold
• Tropical (T) – develops over the tropics;
warm
Cold Air Masses
• Three polar air masses:
– Continental polar (cP) forms over northern
Canada; brings extremely cold weather during
winter; brings cool dry weather during
summer
– Maritime polar (mP) forms over North Pacific
Ocean; cool, very wet; rain and snow during
winter; foggy during summer
– Maritime polar (mP) forms over North Atlantic
Ocean; cool, cloudy and precipitation during
winter; mild, cloudy during summer.
Warm Air Masses
• There are three warm air masses that affect the U.S.
– Maritime tropical (mT) forms over warm water in
the Pacific ocean
– (mT) forms over the Gulf of Mexico and the
Atlantic Ocean; brings hot, humid weather and
hurricanes and thunderstorms during the
summer; In winter, brings mild, cloudy weather
– Continental Tropical (cT) forms deserts of Mexico
and Southwestern U.S.; brings clear, hot, dry
weather during summer
Fronts
• The boundary between air masses of
different densities and different
temperatures
– Cold Front – cold air moves under warm air;
brings thunderstorms
– Warm Front – warm air moves over cold air;
brings drizzly rain followed by clear and warm
weather.
Fronts
• Occluded Front – warm air mass is caught
between two colder air masses. Brings
cool temperature and large amounts of
rain.
• Stationary Front – cold air mass meets
warm air mass; remain separate; not
enough energy to move warm air above
cold air mass; can bring many days of
cloudy, wet weather.
Air Pressure and Weather
• Cyclones – areas in the atmosphere that
has lower pressure than the surrounding
areas and has winds that spiral toward the
center. Brings clouds and rain.
• Anticyclones – the rotation of air around a
high pressure center in the direction
opposite to Earth’s rotation. Brings dry,
clear weather.
Quick Check
• What kind of front forms when a cold air
mass displaces a warm air mass?
A. a cold front
B. a warm front
C. an occluded front
D. a stationary front
Quick Check
A maritime tropical air mass contains
A. cold, dry air.
B. warm, dry air.
C. warm, wet air.
D. cold, wet air.
Quick Check
• A front that forms when a warm air mass is
trapped between two cold air masses and
is forced to rise is a(n)
A. stationary front.
B. occluded front.
C. warm front.
D. cold front.
Global Wind Systems and Weather
Events
• Global Winds
Tornadoes
• Thunderstorms
Cumulonimbus clouds
• Low density
High density
• Low pressure
High pressure
• Air pressure
How would you distinguish between local
winds and global winds?
• What combination of air
produces global winds?
•
What makes global
winds curve rather than
move in straight lines?
• What properties of air
near the ground are likely
to produce a
thunderstorm?
• What combination of
properties describes cold
air?
Global Winds
• Wind is the horizontal movement of air from
an area of high pressure to an area of low
pressure.
• All winds are caused by differences in air
pressure.
• Local winds are winds that blow over short
distances.
• Local winds are caused by unequal heating of
Earth’s surface within a small area.
•
Global Winds
• The unequal heating of Earth’s atmosphere by
sunlight produces global winds.
• The combination of high-pressure polar air and
low-pressure equatorial air produces global
winds.
• The angle at which sunshine strikes Earth’s
surface in MAINLY responsible for the unequal
heating of Earth’s surface.
Global Winds
• Air moves from areas of high pressure to
areas of low pressure.
• Dense, high-pressure air over the poles sinks
and moves towards the low-pressure air over
the equator.
• Less dense, low-pressure air over the equator
rises and moves toward the poles.
• These movements of air are global winds.
• Earth’s spin on its axis makes these winds move
along a curved path (Coriolis effect).
• Northern Hemisphere global winds curve
clockwise.
• Southern Hemisphere global winds curve
counterclockwise.
Tornadoes and Thunderstorms
• Differences in air pressure can also
produce powerful local winds and storms.
• The low density, warm air will form clouds
when it reaches colder air in the sky.
• As low density moisture rises high in the
sky, it may freeze into particles that are
electrically charged.
• These charged particles can produce
lightning and thunder.
Tornadoes and Thunderstorms
• Moist, low pressure air near the ground produce
thunderstorms.
• Thunderstorms form within large cumulonimbus
clouds, also known as thunderheads.
• Tornadoes are swiftly turning, very low-pressure
funnels of air. They produce the fastest moving
winds on Earth.
• Tornadoes develop in low, heavy cumulonimbus
clouds.
• Most likely to occur in spring and summer , often
in the late afternoon when the ground is warm.
• Tornadoes occur more often in the U.S. than in
any other country.
Quick Check
What combination produces global winds?
• A. low-pressure polar air and low-pressure
equatorial air
• B. low-pressure polar air and high-pressure
equatorial air
• C. high-pressure polar air and high-pressure
equatorial air
• D. high-pressure polar air and low-pressure
equatorial air
Quick Check
What is MAINLY responsible for the unequal
heating of Earth’s surface?
• A. the distance of the sun from different parts of
Earth
• B. the angle at which sunshine strikes Earth’s
surface
• C. the material on Earth’s surface
• D. changes in the amount of energy the sun puts
out
Quick Check
What makes global winds curve rather than
move in straight lines?
•
•
•
•
A. differences in air pressure
B. differences in density
C. differences in temperature
D. Earth’s rotation on its axis
Quick Check
What properties of air near the ground are
likely to produce a thunderstorm?
•
•
•
•
A. moist, low pressure
B. dry, low pressure
C. moist, high pressure
D. dry, high pressure
Quick Check
Which combination of properties describe
cold air?
•
•
•
•
A. high density and low pressure
B. low density and low pressure
C. high density and high pressure
D. low density and high pressure
Heat and Weather Patterns
• Tropical storms
Hurricanes
• Tropical depression
• Clockwise
• Eye of a hurricane
Counterclockwise
How does evaporation of water affect weather
and the formation of hurricanes?
• What is the source of
a hurricane’s energy?
• What is the general
name for a powerful
tropical storm?
• Where are tropical
storms born?
• What happens when
moist air rises high
into the sky?
Moisture and Weather Patterns
• Tropical storms are born over warm
water near the equator.
• Very large and powerful tropical storms
with spinning winds are called tropical
cyclones.
• In the Atlantic Ocean and the eastern
Pacific Ocean, tropical cyclones are called
hurricanes.
• In the northwest Pacific Ocean, they are
called typhoons.
Moisture and Weather Patterns
• Energy from the sun warms ocean water.
• Energy absorbed by the ocean water
causes the water on the surface to
evaporate.
• The warm, evaporated water rises.
• This produces an area of low pressure
called a tropical depression.
• This is when clouds begin to form.
Moisture and Weather Patterns
• The air in the center of a depression in the
Northern Hemisphere begins to spin
counterclockwise.
• In the Atlantic Ocean, global winds push
the storm westward.
• As the storm continues to move over warm
water, heat from the water feeds it.
• As its air pressure drops lower its winds
move faster and faster.
Moisture and Weather Patterns
• A hurricane has a typical shape.
• The eye of a hurricane is a place of very low
pressure with no clouds above it.
• In the eye, it is very calm and sunny.
• The most violent winds in a hurricane form the
wall of the hurricane’s eye.
• Eventually, a hurricane will travel over cooler
water or land.
• Once this happens, the hurricane can no longer
feed on heat energy from warm water.
Quick Check
What is the source of a hurricane’s energy?
• A. warm, moist air evaporating from the
sea
• B. cool, moist air evaporating from the sea
• C. warm, dry air evaporating from the sea
• D. warm, moist air condensing from the
sea
Quick Check
The general name for a powerful tropical
storm is a
•
•
•
•
A. tropical depression.
B. tropical cyclone.
C. hurricane.
D. typhoon.
Quick Check
Where are tropical storms born?
•
•
•
•
A. over water near Earth’s poles
B. over land near Earth’s poles
C. over water near the equator
D. over land near the equator
Quick Check
What happens when moist air rises high into
the sky?
• A. It cools and evaporates
• B. It cools and condenses, forming clouds
• C. It warms and evaporates
• D. It warms and condenses
Quick Check
The eye of a hurricane has
•
•
•
•
A. low pressure and high winds.
B. low pressure and no winds.
C. high pressure and high winds.
D. high pressure and no winds.