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1、Severe WeatherA Reading AZ Level T Leveled BookWord Count:1,775Visit www.readinga- for thousands of books and materials.www.readinga-SEVERE WEATHER Written by Bruce D.CooperIllustrated by Cende HillLEVELED BOOK TWritten by Bruce D.CooperIllustrated by Cende HillSEVERE WEATHER www.readinga-Severe Wea
2、therLevel T Leveled Book Learning AZWritten by Bruce D.CooperIllustrated by Cende HillAll rights reserved.www.readinga-Photo Credits:Front cover,page 18:courtesy of OAR/ERL/National Severe Storms Laboratory(NSSL)/NOAA;back cover,page 16:PhotoDisc;title page,pages 14,15,17:courtesy of NOAA/OAR/ERL/Na
3、tional Severe Storms Laboratory(NSSL);page 4:iStockphoto/Tupungato;page 5:Peter Barritt/SuperStock;page 10:Corbis/SuperStock;page 19:robertharding Productions/Newscom;page 21:courtesy of Robert Kaufmann/FEMA;page 22:Mark Hayes/D;page 23:courtesy of Dave Saville/FEMA News Photo CorrelationLEVEL TP383
4、8Fountas&PinnellReading RecoveryDRA3Table of Contents Introduction .4Building Blocks of Weather .5Temperature .6Air Pressure.9Wind.10Moisture .11Thunderstorms .14Tornadoes .18Hurricanes,Typhoons,and Tropical Cyclones .20Blizzards .22Storm Safety .24Glossary .28Severe Weather Level T4IntroductionWeat
5、her can be calm and peaceful,or it can be fierce and violent.We experience fierce,violent weather in the form of storms.Every place on Earth can experience some type of violent storm.We will explore types of violent storms,but first lets look at the causes of weather.Threatening storm clouds gather
6、over a road.5Building Blocks of WeatherWhen you think of good weather,you probably think of sunshine,but you might be surprised to know that the sun is responsible for bad weather,too.In fact,the sun is responsible for all weather.Lets talk about the things that make the weather what it isthe buildi
7、ng blocks of weather.These are temperature,air pressure,wind,and moisture.Lets learn how the sun affects these things.Sun,air,and moisture are the building blocks of weather.Severe Weather Level T6TemperatureWeather is caused by changes in the atmosphere,the air that surrounds Earth.All weather begi
8、ns when energy from the Sun strikes the earth.When sunlight hits the earth,it is either absorbed by the earth or reflected back into the atmosphere.The sunlight that is absorbed changes to heat.This heat comes off the earths surface like heat from a hot stove,and it heats the air that surrounds Eart
9、h.The Earths surface heats the air above it.ATMOSPHERE7Now,not all of the Earth is heated equally.Since the Earth is a giant rotating ball,only half of it is facing the sun at any time.While the sunny side gets heated,the dark side loses heat.In addition,some places absorb more sunlight than others.
10、For example,if sunlight strikes a dark surface,it will be absorbed more quickly,and the surface will get hotter.Also,land heats up more quickly than water.TRY THIS:Unequal HeatingPlace a piece of black paper and a piece of white paper in the sun.Let them sit for a couple of hours.Feel both pieces of
11、 paper before and after.Which one gets warmer?Place a thermometer on each piece of paper to see how much warmer one is than the other.SUNSunlight only hits half the Earth at any one time.Severe Weather Level T8The Suns rays also strike more directly near the equator,which means that water and land a
12、round the equator get hotter.Sunlight strikes areas around the poles at a sharp angle.Angled light does not get absorbed as much as direct light,which explains why the poles are colder.Also,the poles are covered with snow and ice,and these light-colored surfaces do not absorb sunlight as well.The an
13、gle of sunlight creates cold poles and a warm equator.9Air PressureThe air in the atmosphere has weight,and it is being pulled toward the Earth by gravity.Because it is pulled down,it pushes against things.This is what we call air pressure.We know that cold air is heavier than warm air,and because o
14、f this,it pushes down with more pressure.This air is called high-pressure air.Scientists have learned that high-pressure air always moves toward warmer,low-pressure air.The colder air being pulled toward the Earth pushes the warmer air up.WARMAIRCOLDAIRCold air is heavier,while warm air is lighter.S
15、evere Weather Level T10WindWind is caused by the unequal heating of the Earth.The unequal heating causes some air to be warmer than other air,which leads to a difference in air pressure.The unequal heating and the differences in air pressure set air in motion,creating wind.The greater the difference
16、 in temperature and pressure between two large masses of air,the stronger the wind along the borders of these air masses.Wind can be gentle or violent.11MoistureThe Sun also heats water in lakes,rivers,and,most importantly,oceans.The Suns energy causes water to evaporate and form water vapor,which i
17、s an invisible gas.Water vapor in the air has a lot to do with the weather we experience.TRY THIS:Make Your Own CloudWhen you are outside on a cold winter day,you can usually see your breath.This happens in the same way that clouds are formed.The air of your breath is warm and moist.When you breathe
18、 out,the warm,moist air rises and meets the cold outside air.The water vapor in your breath changes to tiny drops of water and turns into a little cloud.Do You Know?It takes about a million cloud droplets to form an average raindrop.Severe Weather Level T12Warm air can hold more moisture than cold a
19、ir,and cold air constantly pushes this warm,moist air upward.As this warm air rises,it cools down,and the water vapor begins to get squeezed out.When this happens,the water vapor changes to tiny water droplets that form clouds.The water droplets continue to cool and join together in clouds.In time,t
20、hey get so big that they are pulled to the earth by gravity.Precipitation is the name we give to this water falling to the earth.Precipitation can be in the form of rain,snow,or ice.The kind of precipitation that falls depends on the temperature in the clouds and the temperature between the clouds a
21、nd the ground.This table shows the conditions needed for different kinds of precipitation.Now that weve learned about the building blocks of weather,lets learn what happens when conditions are extreme.Remember,violent storms happen when temperature,air pressure,wind,and moisture are extreme.13Condit
22、ions Needed for Different Kinds of PrecipitationTemperaturein the cloudsTemperature between the clouds and groundAbove or below freezingBelow freezingAbove freezingAbove freezing in the lower cloud and below freezing in the upper part of the cloud.Also,high winds blowing upward in the cloud.Above fr
23、eezingBelow freezingBelow freezing.May start as ice,then melts,then freezes again as it passes through freezing air near the ground.Above freezingRainSnowSleet and freezing rainHailSevere Weather Level T14Thunderstorms Thunderstorms are the most common type of storm.They usually occur during hot,hum
24、id weather,and they form when warm,moist air rises quickly.Tall clouds form,and large amounts of water vapor in these clouds form water drops very quickly.Do You Know?There are approximately 40,000 thunderstorms in the world every day.Every day someone is struck by lightning.Thunderclouds over the p
25、rairie15Strong wind in a thunderstorm can blow large water drops far up in the cloud,where they freeze.Then they begin to fall and collect more moisture.The wind can blow the ice pellets back up into the cloud,where another layer of ice forms on the pellets.Sometimes this happens many times to the s
26、ame ice pellets.Each time,they get bigger until they become too heavy for the wind to blow them back up.Then they fall as hail.Hailstones the size of baseballs and grapefruits have been reported.The ruler(bottom left)shows the size of this hailstone.Severe Weather Level T16Thunderstorms get their na
27、me from the lightning and thunder they produce.Lightning can go from one cloud to another cloud,or it can go from cloud to ground or from ground to cloud.Lightning,which is very hot,heats the air to cause thunder.The hot air expands very quickly,which creates a shockwave.When the wave reaches your e
28、ar,you hear it as thunder.Lightning usually strikes the tallest object around.17You can tell how far away lightning is by counting the number of seconds between the time you see lightning and the time you hear thunder.If you count five seconds,the lightning is 1.6 kilometers(1 mi)away from you.If yo
29、u count ten seconds,it is 3.2 kilometers(2 mi)away.Do You Know?A bolt of lightning is hotter than the surface of the sun.Severe Weather Level T18TornadoesTornadoes,which have the strongest winds on Earth,have wind speeds that may reach 322 to 480 kilometers per hour(200300 mph).Tornadoes rarely last
30、 more than thirty minutes,but they can do great damage.They can flatten buildings,pick up cars and trucks,and tear out trees by the roots.Tornadoes form when warm air rises very quickly.Cold air rushes in to replace the rising warm air.It moves in so fast that it begins to rotate or spin,and this sp
31、inning causes a funnel cloud to form.Do You Know?On average,the United States experiences 100,000 thunderstorms each year,causing about 1,000 tornadoes.19When a tornado occurs over water,it is called a waterspout.Whirlwinds,sometimes called dust devils,form when hot air spins up from the ground over
32、 bare soil and deserts.These are different from tornadoes and waterspouts,which spin down from clouds.Waterspouts are often beautiful.Severe Weather Level T20Hurricanes,Typhoons,and Tropical CyclonesDuring the warm months of the year,great masses of warm,moist air form over warmer parts of the ocean
33、.They begin to swirl around when cooler air moves in to replace the rising warm air.When this happens,huge storms form.These storms have different names,depending on where in the world they occur.Look at the world map to see what these storms are called in different parts of the world.hurricanehurri
34、canetropical cyclonetropical cyclonetyphoonTropical ocean storms have different names in different parts of the world.21These huge storms can be hundreds of miles across.They have three parts.In the center is the eye of the storm,where the air is calm.The eye is surrounded by a wall of swirling clou
35、ds containing strong,violent winds.These winds whirling around the center can reach over 322 kilometers per hour(200 mph).The third part is the rain bands,which are bands of thunderclouds that reach out from the wall and produce heavy rain.The damage from these storms is done by wind and flooding.Wh
36、en these large storms reach land,they push large mounds of water ahead of them.When these mounds of water hit land,boats and buildings may be swept away and destroyed.The heavy amount of rain can also cause serious flooding.Hurricanes can cause a lot of damage.Severe Weather Level T22BlizzardsThe mo
37、st fierce winter storm is called a blizzard.This is a storm that has heavy snowfall and high winds of over 56 kilometers per hour(35 mph).Sometimes visibility is so limited that the blizzard is called a whiteout.Blizzards can dump several feet of snow quickly.This snow blows around and piles up into
38、 huge drifts of up to 15.2 meters(50 ft).Do You Know?A single snowflake can be made of 50 or more individual ice crystals clustered together.Blizzards make driving very dangerous.23These fierce storms can collapse buildings,bury cars and trucks,and knock out electrical power.In the mountains,heavy s
39、nowfall can lead to avalanches.Avalanches are huge walls of snow that break loose and tumble down a mountainside.They have been known to bury entire villages.An avalanche buried this car.Severe Weather Level T24Storm SafetyIt pays to know what to do when a storm is coming.It can save your life.Here
40、are some safety tips.Thunderstorm Safety Look for shelter,such as a building or car.No matter what,do not take shelter under trees because trees attract lightning.If you are in the open,never lie down on the ground during a storm,because after lightning strikes,it usually spreads out on the ground.T
41、he safest position is to put your feet close together and crouch down with your head as low as possible,curled up in a tight squat.25 Do not stand on a hilltop or open field.If you are in or on the water,get out or get off.Do not carry anything made of metal.Do not use the telephone.If lightning str
42、ikes the phone line,the strike can travel to you if you are holding the phone.If you must call someone,use a cordless phone or a cell phone.Do not use electrical appliances.Lightning could follow the wire.Stay away from plumbing pipes(sink,bathtub,or shower).Lightning can cause an electrical charge
43、in the metal pipes.Severe Weather Level T26Tornado Safety The key word in tornado safety is DOWN.Go to a basement if you can.If you are in a building without a basement,go to a closet or bathroom.In either case,get under a heavy piece of furniture or inside the bathtub and protect your head and neck
44、 with your arms.Mobile homes usually collapse or get blown off their foundations during a tornado.If you are inside one,get outside,preferably to a basement.Otherwise,lie down in a ditch or depression in the ground and protect your head and neck with your arms.Dont get in a car or other vehicle;vehi
45、cles have been blown over a mile away by tornadoes.Stay away from doors and windows.27Hurricane Safety Before a hurricane comes,board up windows.Pick up loose things in the yard.Get a battery-powered radio and store some water.If a hurricane is moving into your area,go to higher ground far inland.If
46、 you cannot leave the area,get inside a concrete building on the highest ground available.Stay away from doors and windows.Do not go outside.Severe Weather Level T28Glossaryair pressure the force of the air in the atmosphere when pulled to Earth by gravity(p.9)atmosphere a layer of gases surrounding
47、 a planet (p.6)avalanche a wall of snow that slides swiftly down a mountain(p.23)blizzard a severe snowstorm with cold temperatures and heavy snow drifts (p.22)dust devils currents of air whirling upward from the ground in a spiral motion(p.19)hail round pieces of ice that sometimes fall during thun
48、derstorms(p.15)precipitation moisture that falls to the ground,such as rain,snow,hail,or sleet(p.12)temperature the degree of hotness or coldness of anything,usually as measured on a thermometer(p.5)water vapor water in the form of gas(p.11)waterspout a whirling,funnel-shaped or tubelike column of air occurring over water,usually in tropical areas(p.19)whiteout a condition that occurs during a severe blizzard when visibility is very limited and everything looks white(p.22)