Download Weather and the water cycle

LZVi]Zg
VcYi]Z
LViZg8nXaZ
Photo Credits: Cover: NASA/Science Photo Library; 3 (t) Joseph Sohm/ChromoSohm
Media/Photo Researchers, Inc.; 6 (t) Joseph Sohm/ChromoSohm Media/Photo
Researchers, Inc., (b) Thomas Wiewandt/ChromoSohm Media/Photo Researchers, Inc.;
8 (r) K.H. Hanel/Panoramic Images/National Geographic Image Collection; 11 K.H.
Hanel/Panoramic Images/National Geographic Image Collection; 12 George Post/Photo
Researchers; 15 (bl) Alden Pellett/The Image Works, (br) Jeff Greenberg/Age Fotostock;
16 (bl) ANA/The Image Works, (br) Mark Antman/The Image Works; 17 Frank S. Balthis;
21 J.A. Kraulis/Masterfile; 22 Matheisl/Getty Images.
If you have received these materials as examination copies free of charge, Harcourt
School Publishers retains title to the materials and they may not be resold. Resale of
examination copies is strictly prohibited and is illegal.
Possession of this publication in print format does not entitle users to convert
this publication, or any portion of it, into electronic format.
LZVi]Zg
VcYi]Z
LViZg8nXaZ
Copyright © by Harcourt, Inc.
All rights reserved. No part of this publication may be reproduced or transmitted
in any form or by any means, electronic or mechanical, including photocopy,
recording, or any information storage and retrieval system, without permission in
writing from the publisher.
Requests for permission to make copies of any part of the work should be
addressed to School Permissions and Copyrights, Harcourt, Inc., 6277 Sea Harbor
Drive, Orlando, FL 32887-6777. Fax: 407-345-2418.
HARCOURT and the Harcourt Logo are registered trademarks of Harcourt, Inc.,
registered in the United States of America and/or other jurisdictions.
Printed in Mexico
ISBN 978-0-15-362063-8
ISBN 0-15-362063-3
2 3 4 5 6 7 8 9 10
805
16 15 14 13 12 11 10 09 08
1
VOCABULARY
atmosphere
troposphere
air pressure
local wind
prevailing winds
L]Vi
8VjhZh
LZVi]Zg4
The atmosphere is a blanket of air surrounding Earth.
The atmosphere is thin compared to the size of Earth. The
atmosphere is made up of several layers. The layer closest
to Earth’s surface is the troposphere. This is where most
of our weather occurs. The troposphere has about 90% of
the gases in the atmosphere.
2
Air pressure is the weight of
air. In the picture, you could
blow through the straw and
make air pressure lift the
book.
A local wind is movement
of air that results from local
changes in temperature.
Prevailing winds are global winds that always blow
from the same direction.
3
READING FOCUS SKILL
B6>C>9:66C99:I6>AH
The main idea is what the text is mostly about. Details
are pieces of information about the main idea.
Look for information about what causes weather and
details about each cause.
I]Z6ibdhe]ZgZ
Earth is surrounded by a blanket of air called the
atmosphere. The atmosphere is made up of layers.
The layer closest to Earth is the troposphere.
Gas molecules in the atmosphere are always moving.
Gravity pulls them toward Earth’s surface. Air pressure is
the weight of the atmosphere pressing down on Earth.
Tell one detail about the atmosphere.
AVnZghd[:Vgi]Éh6ibdhe]ZgZ
4
JcZkZc=ZVi^c\
When the sun’s energy reaches Earth, some of the energy
bounces off objects. Earth takes in the rest of the energy.
Different surfaces take in different amounts of energy. For
example, soil takes in energy from the sun faster than water
does. This means that the sand at a beach heats up faster than
the water does. This causes the air over the sand to be warmer
than the air over the water.
Wind is caused by uneven heating in the atmosphere.
Cool air is denser than warm air. Dense air sinks because it is
heavier. When cool air sinks, less dense air is pushed up. So,
cold air sinks and warm air is pushed up. This movement of air
causes wind.
What causes winds to form?
5
AdXVaL^cYh
Winds always blow from cool areas to warm areas. A local
wind forms when two places in the same area have different
temperatures. Local winds often happen where water and land
meet. During the day, the air over the land is warmer than the
air over the water. So the wind blows from the water toward
the land. This is called a sea breeze. At night, the air over the
water is warmer than the air over the land. So the wind blows
from the land toward the water. This is called a land breeze.
What wind will occur when the air over the land is
warmer than the air over the water?
HZV7gZZoZ
AVcY7gZZoZ
6
EgZkV^a^c\L^cYh
Prevailing winds are global winds that always blow from
the same direction. Prevailing winds are caused by uneven
heating of Earth’s surface. Earth’s movement in space also
plays a part.
Cool air above the Earth’s poles sinks and moves toward the
equator. Warm air above the equator moves up and moves
toward the poles. The air moves on a curved path because of
Earth’s rotation. This rotation causes prevailing winds to blow
mainly from the east or the west.
Why does the air in the
atmosphere move on
a curved path?
<adWVa
L^cYh
Review
8dbeaZiZi]^hbV^c^YZVhiViZbZci#
of Earth’s atmosphere causes wind.
1.
8dbeaZiZi]ZhZYZiV^ahiViZbZcih#
2. A
forms when two places in the same
area have different temperatures.
3.
are global winds that blow from the
same direction.
4. Earth’s
causes air to move in curved paths.
7
2
VOCABULARY
water cycle
evaporation
condensation
humidity
precipitation
L]Vi
8dcY^i^dch
6[[ZXii]Z
LViZg8nXaZ4
Evaporation occurs when
liquid water changes to a
gas.
8
Condensation occurs when
water changes from a gas to a
liquid. When large amounts of
water condense, clouds form.
HaZZi
GV^c
=V^a
Hcdl
Humidity is the amount of water vapor in the air. High
humidity can lead to precipitation. Precipitation is water
that falls from the atmosphere to Earth’s surface. Rain, snow,
sleet, and hail are types of precipitation.
The water cycle is the process by which water moves
from Earth’s surface, to the atmosphere, and back
again.
9
READING FOCUS SKILL
H:FJ:C8:
Sequence is the order in which events take place.
Look for information about the water cycle and the
sequence of steps in which water moves through the
water cycle.
I]ZLViZg8nXaZ
Do you know where fresh water comes from? It comes from
the water cycle. In the water cycle, water moves from Earth’s
surface to the atmosphere and back to Earth’s surface.
Water is found in three states: liquid (water), solid (ice),
and gas (water vapor). During one part of the water cycle,
liquid water on Earth’s surface changes to a gas. Then it moves
into the atmosphere. This process is evaporation.
I]ZLViZg8nXaZ
10
Water remains a gas in warm air. When the air cools, the
water becomes a liquid again. The process of water changing
from a gas to a liquid is called condensation. When large
amounts of water vapor condense, a cloud forms.
When water drops in clouds become heavy enough, they
fall back to Earth’s surface. When the water reaches Earth’s
surface, it may flow into streams or lakes. It may also soak into
the ground and become groundwater. From Earth’s surface,
the water can evaporate and continue the water cycle.
What are the steps in the water cycle?
8adjYh[dgbYjg^c\XdcYZchVi^dc#
11
8adjYhVcYEgZX^e^iVi^dc
When water evaporates, it becomes water vapor. The amount
of water vapor in the air is called humidity. The greater the
amount of water vapor, the higher the humidity. Warm air can
hold more water vapor than cold air can. Warm air is light. So
it moves above cool air. As warm air moves up, it cools. As the
air cools, water vapor begins to condense and form a cloud.
In the cloud, small water droplets join together and form
larger water drops. Eventually the water drops become
too heavy to stay in the cloud. They fall as precipitation.
Precipitation is water that falls from the atmosphere to
Earth’s surface. Rain is a liquid form of precipitation. Snow,
sleet, and hail are solid forms of precipitation.
Water vapor also forms dew. Dew forms when the ground
is cold. Then water vapor in the air above it condenses. When
water vapor turns directly to ice, it forms frost. Fog is formed
when water vapor condenses into droplets close to the ground.
What happens before clouds form?
EgZX^e^iVi^dc[Vaah[gdbXadjYh#
12
;VXidghI]Vi6[[ZXii]ZLViZg8nXaZ
Several factors affect the water cycle. One factor is location.
Areas close to the poles are always cold. So they are more
likely to get snow than areas close to the equator.
Landforms also affect the water cycle. Air has to move over
mountains. As the air moves up a mountain, it cools and
clouds form. This causes rain or snow to fall on one side of the
mountain.
Temperature and landforms affect the water cycle. This
is because they change air pressure. Any other factor that
changes air pressure will also affect the water cycle.
What happens
after air is
pushed up
the side of
a mountain?
Review
8dbeaZiZi]^hhZfjZcXZd[ZkZcih#
1. Water
from a lake and forms water vapor. The
water vapor cools as it rises and
. A cloud forms
from this process.
2. Small water droplets join inside the cloud and form
larger water droplets. When these drops are heavy
enough, they fall to Earth’s surface as
. On
Earth’s surface, water moves into bodies of water. The
water cycle continues when this water
again.
13
3
VOCABULARY
air mass
front
climate
=dl8Vc
EViiZgch^c
LZVi]Zg7Z
DWhZgkZY4
An air mass is a large body of air that has the same
temperature and humidity throughout.
14
A front is the border where two air masses meet.
There are two kinds of fronts: cold fronts and
warm fronts.
B^Vb^7ZVX]!;adg^YV
I]Z6Y^gdcYVX`h!CZlNdg`
Climate is the pattern of weather an area experiences
over a long period of time. Miami Beach and the
Adirondack Mountains have different climates.
15
READING FOCUS SKILL
86JH:6C9:;;:8I
A cause is what makes something happen. An effect
is what happens.
Look for the causes of weather patterns. Look for the
effects of the weather patterns.
BZVhjg^c\LZVi]Zg
We use tools to measure the weather. You might have used
a thermometer. A thermometer measures air temperature.
A hygrometer measures humidity. Humidity is the amount
of water in the air. A barometer measures air pressure.
Air temperature and air pressure are related. A barometer
shows an increase in air pressure as cold air arrives. A rising
barometer also means lower humidity and less chance of rain.
=n\gdbZiZg
7VgdbZiZg
16
Different instruments measure the wind. An anemometer
measures wind speed. Windsocks and wind vanes show wind
direction. Knowing wind direction helps us predict changes in
the weather. For example, suppose you live in the North and
it is winter. Wind blowing from the south will probably bring
warmer weather.
For many years, people simply looked at the sky to predict
the weather. Have you ever seen a red sky in the morning? The
red sky is caused by the rising sun reflecting on storm clouds.
So you can predict it will rain later in the day. Different types
of clouds can also be used to predict weather.
How can you predict the weather by noting the
direction the wind is blowing from?
NdjXVcjhZVlZVi]ZghiVi^dcid
XdaaZXiYViVVcYegZY^Xii]ZlZVi]Zg#
17
6^gBVhhZhVcY;gdcih
Earth’s atmosphere is unevenly heated. This
uneven heating causes Earth’s air to move. Air
moves in regular ways in air masses. An air
mass is a large body of air that has the same
temperature and humidity throughout.
I]ZbVeh]dlhY^[[ZgZci
ineZhd[V^gbVhhZh#
18
Air masses can be warm or cold, humid or dry.
An air mass takes its features from the area over which
it forms. An air mass that forms over a warm sea will
be warm and humid. An air mass that forms over cold
land will be cold and dry.
The map on the facing page shows four kinds of air
masses. Continental polar air masses bring cool, dry
weather. Continental tropical air masses bring hot,
dry weather. Maritime polar air masses bring cool,
humid weather. Maritime tropical air masses bring
warm, humid weather.
One air mass can replace another air mass. The
border where two air masses meet is called a front.
Most weather changes happen along fronts.
6XdaY[gdciWg^c\hXddaZg!
Yg^ZglZVi]Zg#6lVgb[gdci
Wg^c\hlVgbZg!bdgZ]jb^YlZVi]Zg#
19
There are two main kinds of fronts: cold fronts and warm
fronts. A cold front forms when a cold air mass moves under
a warm air mass. The cold air pushes the warm air up. Clouds
form that produce heavy rains or snow. Cold fronts move
quickly.
A warm front forms when a warm air mass moves over a
cold air mass. Clouds also form at this front, but they cause
long, steady rains.
What kind of air mass causes cool, wet weather?
I]^hlZVi]ZgbVeh]dlhVXdaY[gdci#
20
LZVi]ZgEViiZgchVcY8a^bViZh
Most places have a pattern of regular weather. Many places
have temperature patterns. For example, mornings may be
cooler than afternoons. This is because the sun warms up the
air by the afternoon.
We can also see seasonal weather patterns. We see how the
weather changes during the spring, summer, fall, and winter.
The angle of the sun’s rays causes these seasonal weather
patterns. In the warmer months, the longer days warm Earth’s
atmosphere and surface more. In the cooler months, the
shorter days warm Earth’s atmosphere and surface less.
21
Climate is the pattern of weather an area experiences over
a long period of time. Climate and weather are not the same.
Weather is the condition of the atmosphere at a certain time.
Climate is the average weather conditions over many years.
Climate depends on many factors. One factor is how close
an area is to the equator. Areas close to the equator have
warm climates. Another factor is how close an area is to
a large body of water. Areas near water usually have wetter
and milder climates than areas inland.
What causes seasonal temperature patterns?
I]ZigZZh]dlh]dli]ZhZVhdch
X]Vc\Z^cbjX]d[i]ZJc^iZYHiViZh#
22
AVcY[dgbh6[[ZXi8a^bViZ
Mountains are one type of landform that affects climate.
As air moves up a mountain, it cools and forms clouds. These
clouds cause rain or snow to fall on one side of the mountain.
When the air mass reaches the other side of the mountain, it
does not have much water. So one side of the mountain has
a wet climate and the other side has a dry climate.
What causes one side of a mountain to have
a dry climate?
I]ZXa^bViZhdci]Z
ildh^YZhd[i]Z
bdjciV^cVgZkZgn
Y^[[ZgZci#
Review
8dbeaZiZi]ZhZXVjhZVcYZ[[ZXihiViZbZcih#
1. If a barometer shows increasing air pressure, then the
humidity is probably
.
2. If a
air mass moves over an area, then
the weather will become warm and humid.
3. Two air masses meeting causes a
to form.
4. The
that the sun’s rays strike the Earth causes
temperatures to be cooler during the winter months
in the United States.
23
GLOSSARY
air mass (AIR MAS) a large body of air that has the same
temperature and humidity throughout.
air pressure (AIR PREssher) the weight of the atmosphere
pressing down on Earth.
atmosphere (ATsmuhssfeer) the blanket of air
surrounding Earth.
climate (KLYsmuht) the pattern of weather an area
experiences over a long period of time.
condensation (kahnsduhnsSAYsshuhn) the process of a
gas changing into a liquid.
evaporation (eesvapsuhsRAYsshuhn) the process of a
liquid changing into a gas.
front (FRUHNT) the border where two air masses meet.
humidity (hyoosMIDsuhstee) a measurement of the
amount of water vapor in the air.
local winds (LOHskuhl WINDZ) movements of air that
result from local changes in temperature.
precipitation (preessipsuhsTAYsshuhn) water that falls
from the air to Earth.
prevailing winds (preesVAYLsing WINDZ) global winds
that always blow from the same direction.
troposphere (TROHspuhssfeer) the layer of air closest to
Earth’s surface.
water cycle (WAWster SYskuhl) the process in which
water continuously moves from Earth’s surface into the
atmosphere and back again.
24
Think About the Reading
1. What can you do to help you remember what you have
learned in this book?
2. What questions do you have after reading this book? How
can you find the answers to your questions?
Hands-On Activity
Make a model of the water cycle by placing 1 to 2 inches of water
into a clear half-gallon jar. Swirl in a few drops of blue food coloring
and seal the jar. Place the model on a sunny windowsill.
1. Observe evaporation, condensation, and precipitation in
the jar.
2. Explain why the sun’s energy is needed for this activity.
School-Home Connection
Share with a family member what you have learned about
weather and the water cycle. Ask the family member to describe
any climates he or she has lived in, other than the one you both
currently live in.
GRADE 5
Book 11
WORD COUNT
1321
GENRE
Expository NonÞction
LEVEL
See TG or go Online
Harcourt Leveled
Readers Online Database
www.eharcourtschool.com
ISBN-13: 978-0-15-362063-8
ISBN-10: 0-15-362063-3
>
j]Y+6.%3'Z[W