Chapter 11: AtmosphereChapter 11: Atmosphere

EARTH SCIENCEGeology, the Environment and the Universe

Section 11.1 Atmospheric Basics

Section 11.2 Properties of the Atmosphere

Section 11.3 Clouds and Precipitation

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CHAPTER

11 Table Of Contents

Essential Questions

• What is the gas and particle composition of the atmosphere?

• What are the five layers of the atmosphere?

• How is energy transferred in the atmosphere?

SECTION11.1

Atmospheric Basics

Review Vocabulary

• atmosphere: the layer of gases that surrounds Earth

• Energy is transferred throughout Earth’s atmosphere.

SECTION11.1

Atmospheric Basics

New Vocabulary

troposphere

stratosphere

mesosphere

thermosphere

exosphere

radiation

conduction

convection

SECTION11.1

Atmospheric Basics

• Air is a combination of gases, such as nitrogen and oxygen, and particles, such as dust, water droplets, and ice crystals.

SECTION11.1

Atmospheric Basics

Atmospheric Composition

Permanent atmospheric gases

• Earth’s atmosphere consists mainly of nitrogen (78 percent) and oxygen (21 percent).

SECTION11.1

Atmospheric Basics

Atmospheric Composition

Permanent atmospheric gases

• The amounts of nitrogen and oxygen in the atmosphere are fairly constant over time.

SECTION11.1

Atmospheric Basics

Atmospheric Composition

Variable atmospheric gases

• The concentrations of some atmospheric gases are not as constant over time as the concentrations of nitrogen and oxygen.

SECTION11.1

Atmospheric Basics

Atmospheric Composition

Variable atmospheric gases

• The concentration of water vapor in the atmosphere varies with the seasons, with the altitude of a particular mass of air, and with the properties of the surface beneath the air.

SECTION11.1

Atmospheric Basics

Atmospheric Composition

Variable atmospheric gases

• During the past 150 years, the concentration of atmospheric carbon dioxide has increased, due primarily to the burning of fossil fuels.

SECTION11.1

Atmospheric Basics

Atmospheric Composition

• Molecules of ozone are formed by the addition of an oxygen atom to an oxygen molecule.

Variable atmospheric gases

SECTION11.1

Atmospheric Basics

Atmospheric Composition

• The ozone layer blocks harmful ultraviolet rays from reaching Earth’s surface.

Variable atmospheric gases

SECTION11.1

Atmospheric Basics

Atmospheric Composition

• Earth’s atmosphere contains variable amounts of solids in the form of tiny particles, such as dust, salt, and ice.

Atmospheric particles

SECTION11.1

Atmospheric Basics

Atmospheric Composition

• The atmosphere is classified into five different layers: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

SECTION11.1

Atmospheric Basics

Atmospheric Layers

• The layer closest to Earth’s surface, the troposphere, contains most of the mass of the atmosphere and is where weather occurs.

• In the troposphere, air temperature decreases as altitude increases. The tropopause is the altitude at which the temperature stops decreasing.

Troposphere

SECTION11.1

Atmospheric Basics

Atmospheric Layers

• Above the tropopause is the stratosphere, a layer in which the air temperature mainly increases with altitude and which contains the ozone layer.

• At the stratopause, air temperature stops increasing with altitude.

Stratosphere

SECTION11.1

Atmospheric Basics

Atmospheric Layers

• Above the stratopause is the mesosphere, in which air temperature decreases with altitude.

• Temperatures stop decreasing with altitude at the mesopause.

Mesosphere

SECTION11.1

Atmospheric Basics

Atmospheric Layers

• The thermosphere is the layer above the mesopause and contains the ionosphere.

Thermosphere

SECTION11.1

Atmospheric Basics

Atmospheric Layers

• The exosphere is the outermost layer of Earth’s atmosphere and can be thought of as the transitional region between Earth’s atmosphere and outer space.

Exosphere

SECTION11.1

Atmospheric Basics

Atmospheric Layers

SECTION11.1

Atmospheric Basics

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• Earth’s atmosphere is made up of five layers. Each layer is unique in composition and temperature.

SECTION11.1

Atmospheric Basics

Visualizing the Layers of the Atmosphere

SECTION11.1

Atmospheric Basics

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• The total energy of the particles in an object due to their random motion is called thermal energy.

SECTION11.1

Atmospheric Basics

Energy Transfer in the Atmosphere

• Radiation is the transfer of thermal energy by electromagnetic waves.

• Thermal energy is transferred from the Sun to Earth by radiation.

Radiation

SECTION11.1

Atmospheric Basics

Energy Transfer in the Atmosphere

• Incoming solar radiation is either reflected back into space or absorbed by Earth’s atmosphere or its surface.

Radiation

SECTION11.1

Atmospheric Basics

Energy Transfer in the Atmosphere

• The rate of absorption for any particular area varies depending on the physical characteristics of the area and the amount of solar radiation it receives.

Radiation

SECTION11.1

Atmospheric Basics

Energy Transfer in the Atmosphere

• Conduction is the transfer of thermal energy between objects when their atoms or molecules collide.

Conduction

SECTION11.1

Atmospheric Basics

Energy Transfer in the Atmosphere

• Convection is the transfer of thermal energy by the movement of heated material from one place to another.

Convection

Energy Transfer in the Atmosphere

SECTION11.1

Atmospheric Basics

SECTION11.1

Atmospheric Basics

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Oxygen is the most abundant gas in Earth’s atmosphere.

a. true

b. false

SECTION11.1

Section Check

What causes weather on Earth?

a. heat from Earth’s interior

b. heat from the Sun

c. Earth’s magnetic field

d. Earth’s gravity field

SECTION11.1

Section Check

By which criterion are layers of Earth’s atmosphere defined?

a. by how temperature changes with height

b. by how pressure changes with height

c. by the types of clouds that form

d. by the types of precipitation that occur

SECTION11.1

Section Check

Use with Chapter 11Section 11.1

Energy transfer throughout the atmosphere1)What is the source of all energy in the atmosphere?2)List the three methods by which energy is transferred throughout the atmosphere.3)What role does radiation play in warming the atmosphere?4)How does conduction transfer energy throughout the atmosphere?5)How does convection work with conduction to transfer energy throughout the atmosphere?6)Infer how the transfer of energy in the atmosphere would be different without convection.7) Describe how air moves and changes in convection currents in the atmosphere.

Essential Questions

• What are the three main properties of the atmosphere and how do they interact?

• Why do atmospheric properties change with changes in altitude?

Review Vocabulary

• density: the mass per unit volume of a material

SECTION11.2

Properties of the Atmosphere

• Atmospheric properties such as temperature, air pressure, and humidity describe weather conditions.

New Vocabulary

temperature inversion

humidity

saturation

relative humidity

dew point

latent heat

SECTION11.2

Properties of the Atmosphere

• Particles have more kinetic energy when they are moving faster, so the higher the temperature of a material, the faster the particles are moving.

SECTION11.2

Properties of the Atmosphere

Temperature

• Temperature can be measured in degrees Fahrenheit, degrees Celsius, or in kelvins.

Measuring temperature

SECTION11.2

Properties of the Atmosphere

Temperature

• Air pressure is the pressure exerted on a surface by the weight of the atmosphere above the surface.

• The units for pressure are N/m2.

• Air pressure is often measured in units of millibars (mb), where 1 mb equals 100 N/m2.

SECTION11.2

Properties of the Atmosphere

Air Pressure

• The density and pressure of the layers of the atmosphere decrease as altitude increases.

Density of air

SECTION11.2

Properties of the Atmosphere

Air Pressure

• In the atmosphere, the temperature, pressure, and density of air are related to each other.

SECTION11.2

Properties of the Atmosphere

Air Pressure

Pressure-temperature-density relationship

• Temperature, pressure, and density are all related to one another.

• If temperature increases, but density is constant, the pressure increases.

• If the temperature increases and the pressure is constant, the density decreases.

SECTION11.2

Properties of the Atmosphere

Air Pressure

Pressure-temperature-density relationship

• A temperature inversion is an increase in temperature with height in an atmospheric layer.

Temperature inversion

SECTION11.2

Properties of the Atmosphere

Air Pressure

• If the land does not radiate thermal energy to the lower layers of the atmosphere, such as on a cold, clear, winter night when the air is calm, the lower layers of air become cooler than the air above them.

Temperature inversion

SECTION11.2

Properties of the Atmosphere

Air Pressure

• A temperature inversion can lead to fog or low-level clouds.

• In some cities, a temperature inversion can worsen air-pollution problems.

Temperature inversion

SECTION11.2

Properties of the Atmosphere

Air Pressure

• The movement of air is commonly known as wind.

• In the lower atmosphere, air generally moves from regions of higher density and pressure to regions of lower density and pressure.

Wind

SECTION11.2

Properties of the Atmosphere

Air Pressure

• Near Earth’s surface, wind is constantly slowed by the friction that results from contact with surfaces including trees, buildings and hills.

• Higher up from Earth’s surface, air encounters less friction and wind speeds increase.

Wind

SECTION11.2

Properties of the Atmosphere

Air Pressure

• Humidity is the amount of water vapor in the atmosphere at a given location on Earth’s surface.

SECTION11.2

Properties of the Atmosphere

Humidity

• Saturation occurs when the amount of water vapor in a volume of air has reached the maximum amount possible for that temperature.

SECTION11.2

Properties of the Atmosphere

Humidity

Relative humidity

• The amount of water vapor in a volume of air relative to the amount of water vapor needed for that volume of air to reach saturation is called relative humidity.

SECTION11.2

Properties of the Atmosphere

Humidity

Relative humidity

• The dew point is the temperature to which air must be cooled at constant pressure to reach saturation.

SECTION11.2

Properties of the Atmosphere

Humidity

Relative humidity

• The extra thermal energy contained in water vapor compared to liquid water is called latent heat.

SECTION11.2

Properties of the Atmosphere

Humidity

Relative humidity

• A process in which temperature changes without the addition or removal of thermal energy from a system is called an adiabatic process.

• Adiabatic heating occurs when air is compressed, and adiabatic cooling occurs when air expands.

SECTION11.2

Properties of the Atmosphere

Humidity

Condensation level

• At equilibrium, evaporation and condensation occur at equal rates, so the amount of water in the liquid form remains constant.

SECTION11.2

Properties of the Atmosphere

Humidity

Condensation level

• Condensation occurs at the lifted condensation level (LCL). Air above the LCL is saturated and thus cools more slowly than air below the LCL.

SECTION11.2

Properties of the Atmosphere

Humidity

Condensation level

What is the relative humidity of a parcel of air that has reached its dew point?

a. 25 percent

b. 50 percent

c. 75 percent

d. 100 percent

SECTION11.2

Section Check

a. volume

b. density

c. pressure

d. mass

A sealed container holds only air. If the temperature of the air inside the container is increased, which other property of the air also increases?

SECTION11.2

Section Check

During which changes of state does water release latent heat?

a. condensing and freezing

b. evaporating and melting

c. evaporating and freezing

d. condensing and melting

SECTION11.2

Section Check

Essential Questions

• What is the difference between stable and unstable air?

• How do low, middle, high, and vertical development clouds differ?

• How does precipitation form?

SECTION11.3

Clouds and Precipitation

• Clouds vary in shape, size, height of formation, and type of precipitation.

Review Vocabulary

• condensation: process in which water vapor changes to a liquid

SECTION11.3

Clouds and Precipitation

New Vocabulary

condensation nucleus

orographic lifting

cumulus

stratus

cirrus

precipitation

coalescence

SECTION11.3

Clouds and Precipitation

• As a warm air mass rises, it expands and cools adiabatically.

• The cooling of an air mass as it rises can cause water vapor in the air mass to condense.

SECTION11.3

Clouds and Precipitation

Cloud Formation

• A condensation nucleus is a small particle in the atmosphere around which water droplets can form.

• When the number of these droplets is large enough, a cloud is visible.

SECTION11.3

Clouds and Precipitation

Cloud Formation

• As an air mass rises, it cools. However, the air mass will continue to rise as long as it is warmer than the surrounding air.

• When an air mass sinks back to its original position and resists rising, it is considered stable.

Atmospheric stability

SECTION11.3

Clouds and Precipitation

Cloud Formation

• The stability of air masses determines the type of clouds that form and the associated weather patterns.

• Stable air has a tendency to resist movement. Unstable air does not resist vertical displacement.

Atmospheric stability

SECTION11.3

Clouds and Precipitation

Cloud Formation

• When the temperature of a mass of air is greater than the temperature of the surrounding air, the air mass rises. When the temperature of the surrounding air is greater than that of the air mass, it sinks.

Atmospheric stability

SECTION11.3

Clouds and Precipitation

Cloud Formation

• Clouds can form when moist air rises, expands, and cools enough for water vapor to condense.

• Clouds can also form when air is forced upward or lifted by mechanical processes.

Atmospheric lifting

SECTION11.3

Clouds and Precipitation

Cloud Formation

• Orographic lifting occurs when an air mass is forced to rise over a topographic barrier.

Atmospheric lifting

SECTION11.3

Clouds and Precipitation

Cloud Formation

• Air can be lifted by convergence, which occurs when air moves into the same area from different directions and some of the air is forced upward.

• This process is even more pronounced when air masses at different temperatures collide.

Atmospheric lifting

SECTION11.3

Clouds and Precipitation

Cloud Formation

• Clouds are generally classified by the altitudes at which they form and by their shapes.

SECTION11.3

Clouds and Precipitation

Types of Clouds

Low clouds

• Cumulus clouds are puffy, lumpy-looking clouds that usually occur below 2000 m.

• Another type of cloud that forms at heights below 2000 m is a stratus, a layered sheetlike cloud that covers much or all of the sky in a given area.

SECTION11.3

Clouds and Precipitation

Types of Clouds

Middle clouds

• Altocumulus and altostratus clouds form at altitudes between 2000 m and 6000 m and are made up of ice crystals and water droplets.

SECTION11.3

Clouds and Precipitation

Types of Clouds

High clouds

• High clouds, made up of ice crystals, form at heights above 6000 m where temperatures are below freezing. Some, such as cirrus clouds, often have a wispy, indistinct appearance.

SECTION11.3

Clouds and Precipitation

Types of Clouds

Vertical development clouds

• If the air that makes up a cumulus cloud is unstable, the cloud will continue to grow upward through middle altitudes as a towering cumulonimbus. If conditions are right, it can reach the tropopause.

SECTION11.3

Clouds and Precipitation

Types of Clouds

• All forms of water that fall from clouds to the ground are precipitation.

• Rain, snow, sleet, and hail are the four main types of precipitation.

SECTION11.3

Clouds and Precipitation

Precipitation

Coalescence

• Coalescence occurs when cloud droplets collide and join together to form a larger droplet.

• When the droplets become too heavy to remain suspended in the cloud, they fall to Earth as precipitation.

SECTION11.3

Clouds and Precipitation

Precipitation

Snow, sleet, and hail

• The type of precipitation that reaches Earth depends on the vertical variation of temperature in the atmosphere.

SECTION11.3

Clouds and Precipitation

Precipitation

The water cycle

• Water moves from Earth to the atmosphere and back to Earth in the water cycle.

SECTION11.3

Clouds and Precipitation

Precipitation

Which adjective best describes cirrus clouds?

a. dark

b. bulbous

c. wispy

d. tall

SECTION11.3

Section Check

At which setting will orographic lifting occur?

a. a mountain range

b. a flat plain

c. a large forest

d. a sandy desert

SECTION11.3

Section Check

What is an unstable atmosphere?

Answer: An unstable atmosphere refers to a condition in which rising parcels of air continue to rise high into the atmosphere. For this to happen, temperature in the surrounding atmosphere must decrease with height at a faster rate than the rising air mass cools adiabatically.

SECTION11.3

Section Check

CHAPTER

11 Atmosphere

Resources

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Chapter Assessment Questions

Standardized Test Practice

Study Guide

Earth Science Online

• Energy is transferred throughout Earth’s atmosphere.

• Earth’s atmosphere is composed of several gases, primarily nitrogen and oxygen, and also contains small particles.

• Earth’s atmosphere consists of five layers that differ in their compositions and temperatures.

Study Guide

SECTION11.1

Atmospheric Basics

• Solar energy reaches Earth’s surface in the form of visible light and infrared waves.

• Solar energy absorbed by Earth’s surface is transferred as thermal energy throughout the atmosphere.

Study Guide

SECTION11.1

Atmospheric Basics

• Atmospheric properties, such as temperature, air pressure, and humidity describe weather conditions.

• At the same pressure, warmer air is less dense than cooler air.

• Air moves from regions of high pressure to regions of low pressure.

SECTION11.2

Properties of the Atmosphere

Study Guide

• The dew point of air depends on the amount of water vapor the air contains.

• Latent heat is released when water vapor condenses and when water freezes.

SECTION11.2

Properties of the Atmosphere

Study Guide

• Clouds vary in shape, size, height of formation, and type of precipitation.

• Clouds are formed as warm, moist air is forced upward, expands, and cools.

• An air mass is stable if it tends to return to its original height after it starts rising.

Study Guide

SECTION11.3

Clouds and Precipitation

• Cloud droplets form when water vapor is cooled to the dew point and condenses on condensation nuclei.

• Clouds are classified by their shapes and the altitudes at which they form.

• Cloud droplets collide and coalesce into larger droplets that can fall to Earth as rain, snow, sleet, or hail.

Study Guide

SECTION11.3

Clouds and Precipitation

In which layer of Earth’s atmosphere does most of Earth’s weather occur?

a. troposphere

b. stratosphere

c. mesosphere

d. thermosphere

CHAPTER

11 Atmosphere

Chapter Assessment

How is energy moved during the process of convection?

a. by electromagnetic waves

b. by colliding particles

c. by flowing matter

d. by electric currents

CHAPTER

11 Atmosphere

Chapter Assessment

Which cloud type is often associated with strong thunderstorms?

a. cirrocumulus

b. altostratus

c. cirrostratus

d. cumulonimbus

CHAPTER

11 Atmosphere

Chapter Assessment

About how much of Earth’s incident solar radiation is absorbed by Earth’s surface?

a. 20 percent

b. 30 percent

c. 50 percent

d. 60 percent

CHAPTER

11 Atmosphere

Chapter Assessment

An air mass starts to rise, becomes saturated, and continues to rise. How does the rate at which this air mass cools change as it rises?

CHAPTER

11 Atmosphere

Chapter Assessment

Possible answer: The air mass first cools at the dry adiabatic lapse rate, which is about 10C per 1000 meters. After the air reaches its dew point and becomes saturated, it cools more slowly at the moist adiabatic lapse rate, which ranges from about 4C per 1000 meters to about 9C per 1000 meters.

CHAPTER

11 Atmosphere

Chapter Assessment

Which layer of Earth’s atmosphere includes the ozone layer?

a. troposphere

b. stratosphere

c. mesosphere

d. thermosphere

Standardized Test Practice

CHAPTER

11 Atmosphere

Which is a measure of the average kinetic energy of molecules in air?

a. pressure

b. temperature

c. density

d. humidity

Standardized Test Practice

CHAPTER

11 Atmosphere

a. –20C to –10C

b. –10C to 0C

c. 20C to 30C

d. 30C to 40C

Examine the graph showing air’s capacity for water vapor at various temperatures. In which temperature interval does the water vapor capacity increase the least?

Standardized Test Practice

CHAPTER

11 Atmosphere

Which circumstance describes a temperature inversion?

a. warmer air overlies cooler air

b. cooler air overlies warmer air

c. humidity increases with height

d. humidity decreases with height

Standardized Test Practice

CHAPTER

11 Atmosphere

How is wind related to air pressure?

Answer: Wind is the movement of air from a region of high air pressure to a region of low air pressure. Wind is strong if a large pressure change exists through a short distance. Wind is light if the air moves in response to a weak pressure gradient.

Standardized Test Practice

CHAPTER

11 Atmosphere