California Leveled Science Readers (Grade 5) Content leveled readers teach science concepts, vocabulary, and reading skills – at each student’s reading level – and allow students to read and explore the wonders of nonfiction. Leveled science readers deliver science content to help address the individual needs of all students. They reinforce reading skills and strategies while promoting science understanding. Each grade 5 science reader is a richly illustrated, selfcontained little book with 10 to 14 double pages. BELOW 5.1 Building Blocks of Matter (Physical Sciences) 5.2 Changes in Matter (Physical Sciences) 5.3 Basic Structures of Organisms (Life Sciences) 5.4 MISSING 5.5 Water on Earth (Earth Sciences) 5.6 Weather (Earth Sciences) 5.7 The Solar System (Earth Sciences) ON 5.1 Understanding Matter (Physical Sciences) 5.2 How Matter Changes (Physical Sciences) 5.3 The Building Blocks of Organisms (Life Sciences) 5.4 Systems of the Human Body (Life Sciences) 5.5 Earths Hydrosphere (Earth Sciences) 5.6 How Weather Works (Earth Sciences) 5.7 Earths Solar System (Earth Sciences) ADVANCED 5.1 Atoms (Physical Sciences) 5.2 Acids and Bases at Work (Physical Sciences) 5.3 MISSING 5.4 MISSING 5.5 MISSING 5.6 Hurricanes (Earth Sciences) 5.7 The Red Planet (Earth Sciences)
Trang 1Genre Comprehension Skill Text Features Science Content
• Labels
• Charts
• Glossary
Weather
Scott Foresman Science 5.6
Standards Preview
Standard Set 4 Earth Sciences
4 Energy from the Sun heats Earth
unevenly, causing air movements that
result in changing weather patterns
As a basis for understanding this
concept:
4.a Students know uneven heating
of Earth causes air movements
(convection currents).
4.b Students know the influence that
the ocean has on the weather and
the role that the water cycle plays in
weather patterns.
4.c Students know the causes and
effects of different types of severe weather.
4.d Students know how to use
weather maps and data to predict local weather and know that weather forecasts depend on many variables.
4.e Students know that the Earth’s
atmosphere exerts a pressure that decreases with distance above Earth’s surface and that at any point it exerts this pressure equally in all directions.
ISBN 0-328-23468-0
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by Lisa Oram
Earth Sciences
Trang 2air mass
anemometer
atmospheric pressure
barometer
convection current
cyclone
front
rain gauge
tempered
wind
Picture Credits
Every effort has been made to secure permission and provide appropriate credit for photographic material
The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions.
Unless otherwise acknowledged, all photographs are the copyright © of Dorling Kindersley, a division of Pearson.
Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd).
10 (B) PhotoEdit; 12 (TL) Bruce Coleman Inc., (TR) David Frazier/PhotoEdit, (BR) Jim Sugar/Corbis, (BL) Sky Bonillo/
PhotoEdit; 18 (B) Damian Dovarganes/AP/Wide World Photos; 19 (B) Indranil Mukherjee/Getty Images;
22 (B) Tony Freeman/PhotoEdit; 23 (B) Andy Newman/AP/Wide World Photos
ISBN: 0-328-23468-0
Copyright © Pearson Education, Inc All Rights Reserved Printed in the United States of America
This publication is protected by Copyright, and permission should be obtained from the publisher prior to any
prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic,
mechanical, photocopying, recording, or likewise For information regarding permission(s), write to
Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025.
1 2 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06
by Lisa Oram
Trang 3Air Moves
Air is all around you even though you can’t see it Air is a
mixture of gases These gases form our atmosphere There are
different layers in the atmosphere Most of our weather happens
in the layer that is closest to Earth
The air that surrounds Earth is pulled by gravity
Atmospheric pressure, or air pressure, is the weight of air
pushing down on an area Atmospheric pressure changes as
elevation changes There is more atmospheric pressure close to
Earth’s surface Higher air presses down on lower air The air
particles are squeezed tightly together from the weight of the air
above them As you go up, there is less air above you, so there
is less air pushing down The air pressure is lower because the
particles are farther apart
You’ve learned that air is matter
Even if it’s invisible, you know it’s there You can feel the effects in different places Air has mass and takes up space On Earth, it is pulled
by gravity, so it has weight When air particles bump into things, they exert pressure As you move away from Earth’s surface, air particles are more spread out There are fewer particles farther from Earth and fewer things to bump into
The mountains are a good place to learn about air pressure As you hike from a low altitude to a higher one, it can become diffi cult to breathe There
is less air pressure At a high altitude, the oxygen particles are spread far apart Each breath at the top of a mountain contains less oxygen for your body than each breath at the bottom of the mountain
As you go higher, air pressure becomes lower.
Air pressure is lowest where air particles are farthest apart.
Air pressure is highest near Earth’s surface, where air particles are squeezed close together by the weight of the air above.
Higher in the atmosphere, air particles can spread farther apart Air pressure is lower.
3
Trang 4Convection Currents
You’ve learned that distance from Earth affects air pressure
Air temperature also affects air pressure The surface of the
Earth heats unevenly Sunlight heats land and water Land heats
and cools more quickly than water So air over land heats and
cools more quickly than air over water
These temperature differences cause
convection currents to form A convection
current is the rising and sinking of matter
in a circular pattern Cool air is heavier
than warm air When cool air and warm
air are next to each other, cool air sinks
and warm air rises These temperature
differences in air cause wind
Rising air will cool This cooled air is pushed over the water by the rising air below it.
As the cool air sinks below the warm air, it moves from an area
of high pressure to an area
of low pressure Wind
at Earth’s surface
is created.
The cool water won’t
warm the air above it
as much as the land
warms the air above it.
5
Wind
The movement of air due to differences in air pressure
caused by temperature differences is known as wind The
convection current below is happening during the day near the ocean This kind of current can also happen off large lakes The convection current is different during the day than at night Cool air sinks and warm air rises, forming a pattern This circular pattern repeats and can form other patterns of clouds, rain, or air pressure
Convection doesn’t just happen in the air It can affect oceans and even rock layers deep below Earth’s surface
Winds cause currents on the surface of oceans But underwater convection currents form when cold, salty water sinks under warmer water Ocean currents can infl uence climate For example, the Gulf Stream makes northern countries such as Ireland warmer than they would be otherwise Inside Earth, convection currents in the mantle move heat to the surface
Ocean currents are caused by convection currents in water.
The warm land makes air above it warm This warm air is forced up
by the cool air.
Gulf Stream
Trang 5Uneven Heating
Earth is heated unevenly These temperature differences
cause large convection currents The warm tropical areas around
Earth’s equator and the cooler Arctic areas around Earth’s poles
cause huge convection currents of air that circle the planet
The huge convection currents cause regional wind patterns In
the United States, most regional winds blow from west to east
That means weather in Ohio often starts with winds from the
California coast
The huge convection currents that
fl ow around Earth result in
regional wind patterns.
7
Earth spins around an axis that is tilted at a 23.5° angle
Because of this angle, the Sun’s energy hits places near Earth’s equator more directly than places near Earth’s poles The air is warmer where the Sun’s rays are more direct and concentrated
The air is cooler where the Sun’s rays are more spread out The poles are a good example of this The Sun’s energy is spread out over a bigger area This is why polar areas stay cold
Earth’s axis
The equator
The North Pole
The South Pole
Near the poles, the Sun’s rays are more spread out.
Near the equator, the Sun’s rays are more concentrated.
Trang 6Different Air Masses
An air mass is a large body of air with similar properties all
through it Air masses form when air stays over one area for a
period of time and takes on the properties of that area The most
important properties of an air mass are temperature and the
amount of water vapor
There are four basic kinds of air masses They are named
for the areas where they form An air mass over water will have
signifi cant moisture in it Air masses over polar oceans are called
maritime polar air They are wet and cool Air masses near the
equator are called maritime tropical air They are wet and warm
In desert areas like New Mexico, the air is warm and relatively
dry An air mass over the desert is called continental tropical air
Air over land near the poles is called continental polar air
This weather map displays
air pressure, fronts, and
precipitation.
Area of high air pressure Area of low air pressure
Warm front
Cold front Stationary front Snow
Rain
Thunderstorms
Sunny
Cloudy
Partly cloudy
Common Weather Symbols
The weather where you live is determined by air masses
Some weather only happens on the edge of air masses Wind moves air masses The wind may be close to the ground or high above the ground The jet stream is a wind high above the ground It can bring an air mass from Canada down into the United States These air masses are often cold and dry
Fronts
A front is the boundary where two air masses meet Most
air masses over North America move from west to east, so fronts have the same motion
A cold front brings colder air into
an area A warm front brings warmer
air into an area A front that does not move very much or moves back and forth over the same area is called a
stationary front.
Trang 7Highs and Lows
You have probably heard about high or low pressure on
the weather report Wind goes from areas with high pressure
to those with low pressure Cool air is heavier than the same
volume of warm air Cool air is under higher pressure Warm air
is lighter, so it is under lower pressure Low-pressure systems
usually bring wind, clouds, or wet weather High-pressure
systems usually bring good weather
Sometimes high-pressure air surrounds an area of
low-pressure warm air When the warm air at the center rises, the
high-pressure air around it fl ows in to take its place This fl ow of
air forms a wind that spirals inward, called a cyclone.
This weather map shows several areas of high pressure, along
with an area of low pressure in the bottom right-hand corner.
<PHOTO: diagram of cyclone and anticyclone; clocks and arrows to show what clockwise and counterclockwise mean>
11
In the United States, cyclone winds spin in a counterclockwise direction Because of Earth’s rotation, cyclone winds spin in the opposite direction in areas below the equator
Cyclones can bring stormy weather Cyclones that begin over tropical waters can become dangerous hurricanes with heavy rains and high winds
Anticyclones are the opposite of cyclones In an anticyclone, cool air at the center sinks The winds around the cool air spin clockwise and outward in the Northern Hemisphere rather than counterclockwise During an anticyclone, skies are usually clear and weather is often calm
Winds in cyclones spin in opposite directions from those in anticyclones.
Anticyclone
Cyclone
Trang 8Severe Weather
What is your favorite kind of weather? Do you like clear,
sunny days? Or do you prefer the excitement of high winds and
deep snow?
California is a great place to live if you like all kinds of
weather If you travel from the top of the state to the bottom,
you will experience many different climates
With mountains, deserts, an ocean coast, and big cities,
Californians experience a range of weather extremes
Temperatures have been recorded from –45° to 134°F There
could be over 100 inches of rain in one year in one part of
California, and in other parts, there might be no rain at all
Across the United States you can also experience a wide range
of severe weather Tornadoes are common in the Midwest and
Southeast, and hurricanes pound the Gulf and Atlantic coasts
California experiences many kinds of weather.
Thunderstorms
Wind plays an important role in severe weather
Thunderstorms usually begin when moist air rises in strong, fast-moving currents The water in the air condenses into clouds that contain both ice crystals and water droplets When the water begins to fall, some of the air is pulled downward with the rain Next, air is moving upward and downward at the same time Finally, as the clouds become smaller, all air currents move downward, and the storm ends
But what about the thunder in a thunderstorm? Thunder is the sound of air vibrating from the heat of lightning Lightning comes fi rst when a large electrical spark moves between
positively charged and negatively charged parts of a cloud
Lightning is hot, and it heats the air so quickly that it makes vibrations We hear those vibrations as thunder Whenever you see lightning or hear thunder, the safest place to be is indoors
What we see as one fl ash of lightning is often many fl ashes
of both positive and negative charges going up and down.
Trang 9Tornadoes
Thunderstorms can sometimes lead to tornadoes Tornadoes
are funnel clouds that touch the ground Not all thunderstorms
have clouds that become funnel clouds, and not all funnel clouds
become tornadoes
When a thunderstorm forms, the winds can begin to spin
and rise at the same time If the spinning wind tilts upward
on one side and the falling air pushes downward on the other
side, you get a column of spinning air The spinning column is
called a funnel cloud Sometimes called “twisters,” winds inside a
tornado can spin at hundreds of kilometers per hour
If you hear or see a tornado warning, the safest place to be is
a basement If you can’t get to a basement, move to a closet or a
room in the center of a building Stay away from windows that
could break during the storm
A tornado is a rotating column of
air that extends from clouds in a
thunderstorm to the ground.
15
About 1,000 tornadoes occur in the United States each year Most of these occur in the central part of the United States during March, April, and May.
Trang 10Hurricanes
Like tornadoes, hurricanes are systems of spinning winds
Hurricane winds are not as fast as those in a tornado, but they
can be more destructive Hurricanes can last for several days or
a week They can travel over many miles and affect many states
or countries They bring large waves that cause fl ooding Heavy
rains from hurricanes can travel several hundred kilometers
inland Hurricanes sometimes cause tornadoes around them
Hurricanes form over warm ocean water First, there are
thunderstorms The thunderstorms begin to move in a circular
motion As the winds in the thunderstorms blow faster, the
thunderstorms develop into a tropical storm A tropical storm
becomes a hurricane when the sustained winds gain speed The
center of the storm is called the eye of the hurricane The winds
in the eye are mild There is no rain
Hurricanes get their energy
from warm ocean water.
17
When a tropical storm has winds of 39 miles per hour, the National Hurricane Center gives it a name There are six lists
of twenty-three names in order from A to W When all six lists have been used, they start over again Names of hurricanes that cause extensive damage are retired In 2005, there were several strong hurricanes in the United States They caused severe fl ooding in the Southeast For the fi rst time in history, the National Hurricane Center went through its entire list of names
Look at the chart below for other names of hurricanes.
Hurricanes Around the World
Atlantic and Eastern Pacifi c Oceans
Hurricane
Northwest Pacifi c Ocean Typhoon Southwest Pacifi c Ocean Severe tropical cyclone Southwest Indian Ocean Tropical cyclone
North Indian Ocean Severe cyclonic storm