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Figure 11.4 Earth's atmosphere is made up of five layers. Each layer is unique in composition and temperature. As shown, air temperature changes with altitude. When you fly in a plane, you might be flying at the top of the troposphere, or you might enter into the stratosphere.

In the exosphere, gas molecules can be exchanged between the atmosphere and space.



Noctilucent clouds are shiny clouds that can be seen in the twilight in the summer around 50°-60° latitude in the northern and southern hemispheres. These are the only clouds that form in the mesosphere.







Weather balloon



Weather balloon

Space Shuttle (300 km)

SpaceShipOne (100 km)

747 Airliner (13,716 m)

Apache helicopter (4845 m)





Stratosphere Troposphere

Figure 11.5 Different spacecraft can traverse the various layers of the atmosphere. Compare the number of atmospheric layers each spacecraft can reach in its flight path.

Figure 11.5 Different spacecraft can traverse the various layers of the atmosphere. Compare the number of atmospheric layers each spacecraft can reach in its flight path.

Exosphere The exosphere is the outermost layer of Earth's atmosphere, as shown in Figure 11.5. The exosphere extends from about 500 km to more than 10,000 km above Earth's surface. There is no clear boundary at the top of the exosphere. Instead, the exosphere can be thought of as the transitional region between Earth's atmosphere and outer space. The number of atoms and molecules in the exosphere becomes very small as altitude increases.

In the exosphere, atoms and molecules are so far apart that they rarely collide with each other. In this layer, some atoms and molecules are moving fast enough that they are able to escape into outer space.

^P Reading Check Summarize how temperature varies with altitude in the four lowest layers of the atmosphere.

Energy Transfer in the Atmosphere

All materials are made of particles, such as atoms and molecules. These particles are always moving, even if the object is not moving. The particles move in all directions with various speeds—a type of motion called random motion. A moving object has a form of energy called kinetic energy. As a result, the particles moving in random motion have kinetic energy. The total energy of the particles in an object due to their random motion is called thermal energy.

Heat is the transfer of thermal energy from a region of higher temperature to a region of lower temperature. In the atmosphere, thermal energy can be transferred by radiation, conduction, and convection.

Radiation Light from the Sun heats some portions of Earth's surface at all times, just as the heat lamp in Figure 11.6 uses the process of radiation to warm food. Radiation is the transfer of thermal energy by electromagnetic waves. The heat lamp emits visible light and infrared waves that travel from the lamp and are absorbed by the food. The thermal energy carried by these waves causes the temperature of the food to increase. In the same way, thermal energy is transferred from the Sun to Earth by radiation. The solar energy that reaches Earth is absorbed and reflected by Earth's atmosphere and Earth's surface.

Absorption and reflection Most of the solar energy that reaches Earth is in the form of visible light waves and infrared waves. Almost all of the visible light waves pass through the atmosphere and strike Earth's surface. Most of these waves are absorbed by Earth's surface. As the surface absorbs these visible light waves, it also emits infrared waves. The atmosphere absorbs some infrared waves from the Sun and emits infrared waves with different wavelengths, as shown in Figure 11.7.

About 30 percent of solar radiation is reflected into space by Earth's surface, the atmosphere, or clouds. Another 20 percent is absorbed by the atmosphere and clouds. About 50 percent of solar radiation is absorbed directly or indirectly by Earth's surface and keeps Earth's surface warm.

Rate of absorption 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. Different areas absorb energy and heat at different rates. For example, water heats and cools more slowly than land. Also, as a general rule, darker objects absorb energy faster than light-colored objects. For instance, a black asphalt driveway heats faster on a sunny day than a light-colored concrete driveway.

Heat Lamp Fries
Figure 11.6 A heat lamp transfers thermal energy by radiation. Here, the thermal energy helps to keep the french fries hot.

Figure 11.7 Incoming solar radiation is either reflected back into space or absorbed by Earth's atmosphere or its surface. Trace the pathways by which solar radiation is absorbed and reflected.

Figure 11.7 Incoming solar radiation is either reflected back into space or absorbed by Earth's atmosphere or its surface. Trace the pathways by which solar radiation is absorbed and reflected.

Earth Atmosphere Conduction

Conduction irr;Cm


Figure 11.8 Thermal energy is transferred to the burner from the heat source by radiation. The burner transfers the energy to the atoms in the bottom of the pan, which collide with neighboring atoms. As these collisions occur, thermal energy is transferred by conduction to other parts of the pan, including the handle.

Interactive Figure To see an animation of conduction, convection, and radiation, visit

Conduction Another process of energy transfer can occur when two objects at different temperatures are in contact. Conduction is the transfer of thermal energy between objects when their atoms or molecules collide, as shown in Figure 11.8. Conduction can occur more easily in solids and liquids, where particles are close together, than in gases, where particles are farther apart. Because air is a mixture of gases, it is a poor conductor of thermal energy. In the atmosphere, conduction occurs between Earth's surface and the lowest part of the atmosphere.

Convection Throughout much of the atmosphere, thermal energy is transferred by a process called convection. The process of convection occurs mainly in liquids and gases. Convection is the transfer of thermal energy by the movement of heated material from one place to another. Figure 11.8 illustrates the process of convection in a pan of water. As water at the bottom of the pan is heated, it expands and becomes less dense than the water around it. Because it is less dense, it is forced upward. As it rises, it transfers thermal energy to the cooler water around it, and cools. It then becomes denser than the water around it and sinks to the bottom of the pan, where it is reheated.

A similar process occurs in the atmosphere. Parcels of air near Earth's surface are heated, become less dense than the surrounding air, and rise. As the warm air rises, it cools and its density increases. When it cools below the temperature of the surrounding air, the air parcel becomes denser than the air around it and sinks. As it sinks, it warms again, and the process repeats. Convection currents, as these movements of air are called, are the main mechanism for energy transfer in the atmosphere.

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Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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  • cassio
    How radiation, conduction and convection heat the troposphere?
    9 years ago
  • sancho
    How is earths atmosphere heated conduction convection radiation?
    8 years ago
  • ferumbras
    What is the primary source of energy for earth's weather?
    8 years ago
  • kenzie
    How conduction heats the earth?
    7 years ago
  • franziska
    Where and how earth's atmosphere gets it energy from and how it is transferred within the atmosphere?
    5 years ago
  • donnino
    How is earth heated by sun through conduction,convection and radiation with diagrams?
    2 years ago
    How solar radiation is absorbed and reflected?
    1 year ago
  • mario
    Does it stop conduction or convection?
    8 months ago

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