24 3 Solar Energy and Winds Section 24 3 24 3 Solar Energy and by ugc19505


									                                                                                                                             Section 24.3
24.3 Solar Energy and Winds
                                                                                                                             1 FOCUS
  Key Concepts                        Vocabulary                 Reading Strategy                                            24.3.1 Describe the processes by
       What happens to the            ◆   greenhouse effect      Comparing and Contrasting Copy the                                 which solar energy heats the
       energy Earth receives          ◆   wind                   table below. After you read, compare sea
       from the sun?                                             and land breezes by completing the table.                          troposphere.
                                      ◆   local wind
       How is energy transferred
                                                                                                                             24.3.2 Identify local and global winds
                                      ◆   sea breeze
       within the troposphere?        ◆   land breeze             Type of         Day or        Direction of                        and explain how they are
       What causes winds?                                         Wind            Night ?       Air Movement                        produced.
                                      ◆   global winds
       What are some examples         ◆   Coriolis effect         Sea breeze      a.   ?        b.   ?
       of local winds and global      ◆   monsoon                                 c.   ?        d.   ?
                                                                  Land breeze
       winds?                         ◆   jet stream                                                                           Reading Focus

                                                                                                                             Build Vocabulary                         L2
                                                                                                                             Concept Map Have students construct
T   he heat you feel when you’re out in the sun is one effect of solar
energy. You might think that sunlight heats the air directly, just as it           20% of incoming
                                                                                                                             a concept map connecting the main
                                                                                                                             topic of Wind to local winds and global
                                                                                   sunlight absorbed                         winds. Have students expand the map as
heats you directly. But the process is more complicated than that.                by clouds and gases           25%
                                                                                                            reflected by
                                                                                                                             they read to include sea breeze, land
                                                                                  50%                       clouds, dust,    breeze, monsoon, and jet stream.
Energy in the Atmosphere                                                       absorbed          5%
                                                                                                              and gases
                                                                               by surface     reflected
    Some solar energy that reaches Earth’s atmosphere is                                      by surface                     Reading Strategy                         L2
reflected back, some is absorbed by the atmosphere, and
                                                                                                                             a. Day b. Cool air moves toward land.
some is absorbed by Earth’s surface. About 30 percent of
                                                                                                                             c. Night d. Cool air moves toward
the incoming solar energy is reflected back into space by
                                                                                                                             the water.
clouds, dust in the air, gases, and Earth’s surface. About 20
percent of the sun’s energy is absorbed by clouds and gases.
But the greatest amount of solar energy—about half—passes                                                                    2 INSTRUCT
through the atmosphere and is absorbed by the surface.
    The atmosphere is heated primarily by energy that is                                                                     Energy in the
reradiated by Earth’s surface. Unlike incoming solar
energy, which has much of its energy in the visible spec-
                                                                                                         Most energy         Build Reading Literacy                   L1
trum, the energy radiated back into the atmosphere is                                                  absorbed by the
mostly infrared radiation. Certain gases in the atmosphere,                                          surface is reradiated   Summarize Refer to page 598D in
including water vapor and carbon dioxide, allow visible                                                  back into the       Chapter 20, which provides the
light to pass through but absorb most infrared radiation.                                                                    guidelines for summarizing.
These gases radiate some of this absorbed energy back to                                                                     Tell students that pp. 755–756 cover
Earth’s surface, warming the lower atmosphere in a                                                                           technical material, and that summarizing
process called the greenhouse effect. Without the green-                                                                     it will help them pull together the main
                                                                                  Figure 11 About half of the
house effect, Earth’s surface would be much cooler than it is.                    sunlight that reaches Earth is             ideas and avoid getting lost in the
         Energy is transferred within the troposphere in three ways:              absorbed by the surface. The rest          details. Allow students to choose
                                                                                  is either reflected back into space
radiation, convection, and conduction. As the How It Works box on                 or absorbed in the atmosphere.
                                                                                                                             whether they would like to present a
page 756 explains, these processes work together to heat the troposphere.                                                    verbal, written, or pictorial summary.
                                                                                                                             Point out to students that the bolded
                                                                                           Weather and Climate 755           key concepts on p. 755 and A, B, and C
                                                                                                                             in How It Works on p. 756 contain
                                                                                                                             important information that should be
                                                                                                                             included in a summary. Intrapersonal
        Section Resources
    Print                                                     Technology
    • Reading and Study Workbook With                         • Interactive Textbook, Section 24.3
      Math Support, Section 24.3                              • Presentation Pro CD-ROM, Section 24.3                        Students may think that the greenhouse
    • Transparencies, Section 24.3                            • Go Online, NSTA SciLinks, Winds                              effect is always bad, possibly because it is
                                                                                                                             often mentioned in conjunction with
                                                                                                                             global warming. Have students write a
                                                                                                                             paragraph describing what Earth would
                                                                                                                             be like without the greenhouse effect.
                                                                                                                             (Earth’s surface would be much colder,
                                                                                                                             possibly inhospitable to life.) Logical

                                                                                                                                           Weather and Climate 755
Section 24.3 (continued)

                                                         Energy Transfer in
Energy Transfer in                                       the Troposphere
the Troposphere                         L2               Energy is transferred within the troposphere by radiation,
Solar radiation heats Earth’s surface,                   conduction, and convection. Radiation from the sun heats
which, in turn, transfers energy to the                  Earth’s surface, which then radiates heat skyward. The air             Solar               Infrared
troposphere. Energy is released by Earth’s               in direct contact with Earth’s surface is heated by                    radiation           radiation
surface in the form of infrared radiation.               conduction. Warm air near the surface expands and rises           Greenhouse effect
Atmospheric gases—such as water vapor,                   and cooler, denser air sinks, forming convection currents         When Earth’s surface is heated,
                                                                                                                           much of this energy is radiated
carbon dioxide, and methane—absorb                       that move heat through the troposphere.                           back as infrared radiation. Some
infrared radiation. These greenhouse                     Interpreting Diagrams Where does most of the energy               of this radiation is absorbed by
gases also reradiate some of that energy                 in the troposphere originally come from?                          gases in the atmosphere. The
back to Earth’s surface. This transfer of                                                                                  process by which gases hold
                                                                                                                           heat in the air is called the
energy by radiation is very efficient, and                    Radiation Much of the sun’s                                  greenhouse effect.
is the primary mechanism by which                             radiation reaches Earth’s
                                                         surface, where it heats the land and
the troposphere is heated. Because in                    water. Land and water radiate heat
convection some heat energy is con-                      back into the atmosphere.
verted into kinetic energy, convection
is a less efficient way of transferring heat
to the troposphere. Because air is not a
good heat conductor, conduction is the
least significant way in which heat is
transferred in the troposphere.
Interpreting Diagrams The sun

For Enrichment                          L3
Students can research the specific
wavelengths of infrared radiation that
are absorbed by each of the major gases
in the atmosphere. Verbal, Portfolio

Integrate Physics                       L2
The sun emits energy over a wide range
of wavelengths, from radio waves
through X-rays. Slightly more than half
of the sun’s radiation is in the visible and
ultraviolet spectra (10–750 nm). Most                                                                                     Convection Convection moves heat
                                                                    Conduction The conduction                             through the troposphere. As surface
of the radiation in this range passes                               process transfers heat from land               air is heated by radiation and conduction,
through the atmosphere and is absorbed                        and water directly to the few meters                 rising warm air is replaced by denser,
by Earth’s surface, heating the land and                      of air nearest Earth’s surface.                      downward-flowing cool air.
water. These surfaces then radiate energy
back into the atmosphere in the infrared
                                                   756     Chapter 24
spectrum (750–1000 nm). Certain gases
in the atmosphere, including carbon
dioxide and water vapor, efficiently
absorb infrared radiation. This process is
called the greenhouse effect, which is         Facts and Figures
the accumulation of heat in the lower
atmosphere through the radiation and           Radiation and Temperature The reason                    wavelength visible and ultraviolet spectrum.
reradiation of energy. Ask, Why is             that the sun and the Earth emit different forms         Earth’s cooler surface (including the people on
only 20% of incoming solar energy              of radiation is because they have different             it) emits radiation in the longer-wavelength
absorbed by the atmosphere? (Most              temperatures. Hotter objects emit shorter-              infrared spectrum. Objects that are colder than
solar radiation is in the visible and ultra-   wavelength radiation. Colder objects emit               freezing emit even longer-wavelength radiation,
violet range, which most atmospheric           longer-wavelength radiation. The sun’s hot              in the microwave spectrum.
gases cannot absorb.) Which has more           surface emits radiation in the shorter-
energy, infrared or ultraviolet
radiation? (Ultraviolet) Logical

756 Chapter 24
What happens when you open a vacuum-packed can of chips? You
hear a rush of air, which is the sound of air moving from the high-
pressure area outside the can to the low-pressure area inside the can.              For: Links on winds
A similar process occurs in the atmosphere.                                         Visit: www.SciLinks.org
                                                                                                                           Wind Creation                            L2
     Air naturally flows from areas of higher pressure to areas of lower             Web Code: ccn-3243

pressure. This flow is wind, which is the mainly horizontal movement                                                        Purpose Students observe how winds
of air.     Winds are caused by differences in air pressure. Larger                                                        are produced.
pressure differences produce stronger winds.                                                                               Materials clear plastic tank, plastic
     Differences in air pressure are often caused by the unequal heating                                                   wrap, 2 1-L beakers, water, hot plate
of Earth’s surface. As you’ve learned, the atmosphere is warmed largely                                                    or Bunsen burner, ice, wood splint
by reradiation from Earth’s surface below it. As air is heated, it expands.                                                (smoker), matches
As it becomes less dense, air rises. Cooler, denser air flows in to replace                                                 Procedure Fill one beaker about
it. This process occurs on both local and global scales, producing local                                                   halfway with water and heat it to nearly
and global winds.                                                                                                          boiling. Fill the other beaker with ice.
                                                                                                                           Place the beakers inside the tank on
Local Winds                                                A    Sea Breeze
                                                                                                                           opposite sides and cover the tank with
On a hot summer day, there is often a cool breeze                                                                          plastic wrap. Cut a small hole in the wrap
blowing in from the water to the beach. This breeze                                                                        over the ice large enough to fit the splint
                                                                                              Warm air
is an example of a local wind, a wind that blows                                               rising
                                                                                                                           through easily. Ask students which way
over a short distance. Local winds are caused by                                                                           they think the wind will blow. Light the
the unequal heating of Earth’s surface within a
                                                               Cooler air                                                  splint, blow on it until it is smoking, and
                                                             moving toward
small region.                                                                                                              insert it deep into the tank over the ice.
                                                                the land
        The breezes that occur where land meets a                                                                          Expected Outcome The smoke will
large body of water are examples of local winds.                                                                           sink over the ice, move across the tank,
Water has a higher specific heat than land, and there-                                                                      and rise over the hot water, making the
fore takes longer to heat up and cool down. During                                                                         movement of air in the convection
the day, the sun heats the land more quickly than it                                                     Cooler air        current visible. Visual, Logical
                                                            B                                          Cooler air
heats the water. The air above the land becomes             B   Land Breeze                          moving toward
warmer than the air above the water. The warm air                                                      the water
expands and rises, creating a lower-pressure area                                                                          Local Winds
above the land. The cooler air over the water flows                                                                         Build Science Skills                     L2
toward the land, creating a sea breeze.                            Warm air                                                Designing Experiments Have groups
    At night, these temperature and pressure con-                   rising
                                                                                                                           of students design an experiment to test
ditions are reversed, as Figure 12 shows. Land cools                                                                       whether a breeze over a lake is produced
off more quickly than water. The cooler air over                                                                           by the same process described on p. 757.
land has a higher density than the warmer air over                                                                         Provide them with the following headings
water. The result is a land breeze, where cooler air                                                                       to fill in: Hypothesis, Materials, Procedure,
over land moves toward water. Winds are named                                                                              and Observations. Students’ experiments
for the direction from which they originate—sea                                                                            may include observations of air pressure,
breezes begin over the ocean and land breezes                   Figure 12 Sea breezes and land breezes are local           temperature, and/or wind direction.
                                                                winds. A During the day, air pressure differences due to
begin over land.                                                unequal heating cause a sea breeze. B At night, pres-
                                                                                                                           Interpersonal, Portfolio
                                                                sure differences are reversed, causing a land breeze.
                         In which direction does a              Comparing and Contrasting How are land
                         land breeze blow?                      breezes and sea breezes different?

                                                                                         Weather and Climate 757

                                                                                                                             Download a worksheet on winds
                                                                                                                             for students to complete, and find
  Customize for English Language Learners                                                                                    additional teacher support from
                                                                                                                             NSTA SciLinks.
   Flowchart                                                     Energy. Use three boxes entitled Sun, Earth’s
   Tailor your presentation to ELL students by                   Surface, and Troposphere. Have students fill
   using a flowchart to help students visualize                  in the boxes to explain the energy transfer in
   the sequence of events with minimal use of                    their own words.                                           Answer to . . .
   language. Title the flowchart The Path of
                                                                                                                            Figure 12 They occur at different
                                                                                                                            times and move in opposite directions.
                                                                                                                                            A land breeze blows
                                                                                                                                            from the land toward
                                                                                                                            the water.

                                                                                                                                         Weather and Climate 757
Section 24.3 (continued)                                                          Dry air sinks                                   Earth’s rotation
                                                                                over the world’s
Global Winds                                                                                                                              Polar easterlies

Use Visuals                             L1
Figure 13 Identify 0 , 30 S, 60 S,
30 N, and 60 N. Explain that the global
wind patterns shown in this figure remain                   Warm air rises
fairly constant throughout the year,                     at the equator until                                Trade winds
though the change of seasons does have                    it reaches the top
                                                         of the troposphere.
some effect on the circulation of the
atmosphere. Heating patterns change as                                                                                                                        The area where
                                                                                                                                                             the trade winds
the seasons change, and patterns of air                                                                                                                      die out is known
pressure (and thus wind) change as a                                                                                                                         as the doldrums.
result. Point out that convection cells are
vertical and reach to the top of the                                                                                    Trade winds
troposphere. Point to the convection cell
between 0 and 30 S and ask, Which                                   The circulating
                                                                     air patterns                               Westerlies
direction is this wind pattern felt on                                are called
the ground? (Northwest) In which                                  “convection cells.”
regions of Earth are the global winds                                                                                                    Very cold air sinks
moving generally from the east in a                                                                                                    at the poles and flows
                                                   Figure 13 Earth is surrounded by                                                   outward, creating winds
westerly direction? (0°–30° N, 0°–30° S,           a set of global wind belts.                                                         called polar easterlies.
60° N–90° N, and 60° S–90° S) Why are
the arrows in the 0 –30 S region (over                                                      Global Winds
South America) curving to the left? (The                                                    Winds that blow over long distances from a specific direction are
northerly winds curve westward as the result       Figure 14 For hundreds of years,
                                                                                            called global winds. These winds are part of a worldwide pattern of
                                                   sailing ships have relied on global
of Earth’s rotation—or the Coriolis effect.)       winds to transport cargo across          air circulation. Global winds are caused by the unequal heating of
This figure can be used to help explain            the oceans.                              Earth’s surface across a large region.
the movements of fronts and storms in              Interpreting Visuals Which
                                                   band of global winds would a
Section 24.5 and global climate patterns           sailing ship use to move cargo           Convection Cells Global winds move in a series of huge bands
in Section 24.7. Visual                            from Canada to Europe?                   called convection cells. As you can see in Figure 13, these bands look
                                                                                            like loops from the side. These bands are caused by temperature vari-
                                                                                            ations across Earth’s surface. At the equator, for example, temperatures
                                                                                            tend to be warmer than at other latitudes. Warm air rises at the equa-
                                                                                            tor, creating a low-pressure region. This warm air is replaced by cooler
Convection Cells                        L2                                                  air brought by global winds blowing near the surface. Higher in the
Purpose Students observe a convection                                                       atmosphere, air blows away from the equator toward the poles. Similar
cell produced in water.                                                                     convection cells cover large bands of latitude across Earth.
                                                                                                 The trade winds are wind belts just north and south of the equator.
Materials 1-L beaker, water, hot plate
                                                                                            In the Northern Hemisphere, they blow from the northeast to the south-
or Bunsen burner, 5–10 drops of food
                                                                                            west. The prevailing westerlies occur between 30° and 60° latitude in
                                                                                            both hemispheres. These winds generally blow from west to east over
Procedure Fill the beaker with                                                              much of North America. The polar easterlies extend from 60° latitude to
approximately 750 mL water. Place the                                                       the poles in both hemispheres.        Trade winds, westerlies, and polar
beaker on a hot plate or Bunsen burner                                                      easterlies are examples of global winds.
and heat water until some steam is rising,
but before boiling. Turn off the heat
source. Explain that convection cells are          758
common phenomena in both air and
water on many scales, from global to
local winds, and from ocean currents to
coffee cups. Slowly add the drops of food      Facts and Figures
coloring (they will spread quickly, so only
add enough to make the convection cell         Where the Wind Dies While trade winds                      wind regions at 30 north and south latitude
visible). Ask students to explain what is      and westerlies occur where convection cells                are called the horse latitudes. This name has
causing the convection cell.                   blow across the surface, there are also areas              a gruesome historical origin. Colonial sailors
Expected Outcome The food coloring             where the wind dies out. These occur where                 traversing the Atlantic would frequently get
will reveal the circulation of water in a      the convection cells produce areas of rising or            stuck around 30 N when the wind died. To
convection cell before dissipating. This       sinking air, such as at the equator, at 30 north           survive at sea with a limited supply of fresh
cell is produced when warm water               and south latitude, and at 60 north and south              water on board (and to lighten the ship’s
touches surface air, cools, and sinks again    latitude. The area of low winds at the equator             weight) the sailors would throw a few horses
to the bottom. Visual, Logical                 is referred to as the doldrums, and the low

758 Chapter 24
    If Earth were not rotating on its axis, global winds would move in
                                                                                                                            3 ASSESS
                                                                               A    Non-rotating Earth
roughly straight paths from the poles to the equator. However, because                            Movement of              Evaluate
Earth rotates, global winds move in a curved path between the poles                                  rocket                Understanding                            L2
and the equator. Notice in Figure 13 that global winds curve to the                                                        Ask students to create a flowchart
right in the Northern Hemisphere and to the left in the Southern                                      Equator              describing how local winds are created.
Hemisphere. The curving effect that Earth’s rotation has on all free-
moving objects, including global winds, is called the Coriolis effect. If                                                  Reteach                                  L1
Earth were not rotating, a rocket launched from the North Pole toward
                                                                                              B   Rotating Earth           Use Figure 13 to explain convection cells
the equator would move in a straight line, as shown in Figure 15.                                                          and the Coriolis effect.
However, because Earth is rotating underneath the rocket, the rocket               Movement of
would appear to an observer on Earth to curve to the right. Similary,
Earth’s rotation causes global winds to curve.                                     Equator
                                                                                     Direction of
Monsoons Seasonal changes in the heating of Earth’s surface affect                 Earth’s rotation
the circulation of the atmosphere. A monsoon is a wind system that is                                                      Water has a high specific heat, higher
characterized by seasonal reversal of direction. Monsoons are similar to       Figure 15 The Coriolis effect               than that of land. As a result, water
                                                                               causes free-moving objects, such
land and sea breezes except that they occur on a much wider scale and          as rockets and global winds, to
                                                                                                                           warms up slower during the day and
longer time frame. For example, the summer monsoon that occurs over            move in a curved path. A A rocket           cools down slower at night than land.
much of South and Southeast Asia blows warm, humid air from the                launched from the North Pole                This affects the temperature of the air
                                                                               toward the equator would move
ocean onto land. As this air rises over land, it cools and brings heavy        in a straight line if Earth were not
                                                                                                                           above the water and land. Land and sea
rainfall to parts of that region. In winter the monsoon reverses, blowing      rotating. B The Coriolis effect             breezes are created by this daily cycle of
from land onto water and bringing drier weather.
                                                                               causes such a rocket to appear to           unequal heating of air in coastal regions.
                                                                               curve to the right. Similarly, the
                                                                               Coriolis effect causes global winds
Jet Stream Global wind patterns are also affected by fast-moving               to curve to the right in the                                If your class subscribes to
streams of air at high altitudes. A belt of high-speed wind in the upper       Northern Hemisphere.
                                                                                                                           the Interactive Textbook, use it to
troposphere is called a jet stream. Jet streams are caused by great dif-                                                   review key concepts in Section 24.3.
ferences in air pressure that develop at high altitudes.

Section 24.3 Assessment

   Reviewing Concepts                                      7. Applying Concepts You and your family
     1.       What happens to solar energy when it            vacation at a cabin on the shore of a large
          reaches Earth’s atmosphere?                         lake. At night, you notice that a breeze blows
                                                              over your cabin toward the lake. Explain what
     2.       Explain how energy is transferred within
                                                              causes the wind to blow in that direction.
          the troposphere.
     3.       What causes the wind to blow?
     4.       How are local winds and global winds
          similar? How are they different?
     5.   What are monsoons, and what causes them?
                                                              Thermal Energy Recall what you learned
   Critical Thinking                                          in Chapter 16 about the specific heat of
     6. Relating Cause and Effects How does the               water. Use this information to explain why
        Coriolis effect influence global wind patterns?        land and sea breezes undergo daily rever-
                                                              sals in direction.
                                                                                                                             Answer to . . .
                                                                                                                             Figure 14 A sailing ship would use
                                                                                    Weather and Climate 759                  the westerlies to move cargo from
                                                                                                                             Canada to Europe.

   Section 24.3            Assessment                      the unequal heating of Earth’s surface. For                6. The Coriolis effect causes global winds to
                                                           local winds, this unequal heating takes place              turn to the right in the Northern Hemisphere
   1. Solar energy is distributed in three ways:           within a small region, and the resulting wind              and to the left in the Southern Hemisphere.
   some is reflected, some is absorbed by the              blows over only a short distance. In contrast,             7. When night falls, the lake water remains
   atmosphere, and some is absorbed by Earth’s             global winds are caused by unequal heating                 warm as the land cools off quickly. The warmer
   surface.                                                across a large area, and blow over long                    air over the water has a lower pressure than
   2. Energy is transferred within the troposphere         distances for extended periods of time.                    the cooler air over the land. The result is a land
   by radiation, convection, and conduction.               5. Monsoons are large wind systems that                    breeze, which is when the cooler air over land
   3. Wind is caused by differences in air                 have seasonal reversals of direction. They are             moves toward water.
   pressure between different locations.                   caused by air pressure differences that result
   4. Both local and global winds are produced             from the unequal heating of air above the
   by differences in air pressure that result from         ocean and land.

                                                                                                                                         Weather and Climate 759

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