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1 What Is Climate? Name Class Date CHAPTER 17 Climate SECTION 1 What Is Climate? National Science BEFORE YOU READ Education Standards After you read this section, you should be able to answer ES 1f, 1j, 3d these questions: • What is climate? • What factors affect climate? • How do climates differ around the world? What Is Climate? How is weather different from climate? Weather is STUDY TIP the condition of the atmosphere at a certain time. The Ask Questions As you read weather can change from day to day. In contrast, climate this section, write down any questions that you have. describes the average weather conditions in a region over When you fi nish reading, talk a long period of time. The climate of an area includes the about your questions in a area’s average temperature and amount of precipitation. small group. Different parts of the world have different climates. What Factors Affect Climate? Climate is mainly determined by temperature and pre- cipitation. Many factors affect temperature and precipi- tation, including latitude, wind patterns, landforms, and ocean currents. READING CHECK 1. List What are the two SOLAR ENERGY AND LATITUDE main things that determine Remember that the latitude of an area is its distance climate? north or south of the equator. In general, the temperature of an area depends on its latitude. Latitudes closer to the poles tend to have colder climates. Latitude affects tem- perature because latitude determines how much direct solar energy an area gets, as shown in the figure below. 4HESUNSRAYSTRAVELINPARALLEL STRAIGHTLINES 4HESUNSRAYSHITTHEEQUATOR ATNEARLYAANGLE4HE ENERGYISFOCUSEDONASMALL AREAOF%ARTH4HESMALLAREA ABSORBSALLOFTHEENERGY SO ITTENDSTOHAVEHIGH TAKE A LOOK TEMPERATURES 2. Explain Why do areas %QUATOR 4HESUNSRAYSHITTHEPOLESAT near the equator tend to ASMALLERANGLETHANATTHE EQUATOR4HEENERGYISSPREAD have high temperatures? OVERALARGERAREA%ACHPART OFTHEAREAABSORBSLESS ENERGY SOTHEAREATENDSTO HAVELOWTEMPERATURES Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 325 Climate Name Class Date SECTION 1 What Is Climate? continued STANDARDS CHECK LATITUDE AND SEASONS ES 3d The sun is the major Most places in the United States have four seasons source of energy for phenomena during the year. However, some places in the world do on the earth’s surface, such as growth of plants, winds, ocean not have such large seasonal changes. For example, currents, and the water cycle. places near the equator have about the same tempera- Seasons result from variations in the amount of the sun’s energy tures and amounts of daylight all year. hitting the surface, due to the tilt Seasons happen because Earth is tilted on its axis by of the earth’s rotation on its axis and the length of the day. about 23.5°. This tilt affects how much solar energy an area gets as Earth orbits the sun. The figure below shows Word Help: major of great importance or how Earth’s tilt affects the seasons. large scale Winter During its winter, the Northern Hemisphere is tilted Word Help: energy away from the sun. It receives less the ability to make things direct sunlight than the Southern Hemisphere. Therefore, the North- happen ern Hemisphere experiences lower March 21 temperatures and shorter days. Word Help: phenomenon Spring any fact or event that December 21 June 21 can be sensed or described Winter scientifi cally (plural, Summer phenomena) September 22 Summer During its summer, the Fall Northern Hemisphere is tilted toward the 3. Explain Why don’t sun. It receives more direct sunlight than areas near the equator the Southern Hemisphere. Therefore, Areas near the equator do not tilt the Northern Hemisphere experiences toward or away from the sun very much. have large seasonal warmer temperatures and longer days. Therefore, they do not experience large changes in weather? changes in weather during the year. PREVAILING WINDS Prevailing winds are winds that blow mainly in one direction. The wind patterns on Earth are caused by the uneven heating of Earth’s surface. This uneven heating forms areas with different air pressures. Wind forms when air moves from areas of high pressure to areas of READING CHECK low pressure. 4. Identify What causes Prevailing winds affect climate and weather because wind to form? they move solar energy from one place to another. This can cause the temperature in one place to decrease and the temperature in another place to increase. Prevailing winds also affect the amount of precipita- tion an area gets. They can carry water vapor away from the oceans. The water vapor can condense and fall to the land somewhere far from the ocean. The figure on top of the next page shows the major prevailing winds on Earth. Notice that most prevailing winds blow from west to east or from east to west. Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 326 Climate Name Class Date SECTION 1 What Is Climate? continued 90°N PolarPolar easterlies easterlies 60°N PrevailingPrevailing westerlies 30°N Trade windswinds Trade winds 0° Equator Trade windswinds Trade winds 30°S TAKE A LOOK PrevailingPrevailing westerlies 5. Read a Map In which 60°S direction do the Prevailing Westerlies blow? PolarPolar easterlies easterlies 90°S Wind direction TOPOGRAPHY The sizes and shapes of the land-surface features of a region form its topography. The topography of an area affects its climate because topography can affect temperature and precipitation. For example, elevation is a feature of topography that can have a large impact on temperature. Elevation is the height of an area above sea level. As elevation increases, temperature tends to decrease. READING CHECK Mountains can also affect precipitation. As air rises to 6. Describe In general, move over a mountain, it cools. The cool air condenses, how does elevation affect forming clouds. Precipitation may fall. This process temperature? causes the rain-shadow effect, which is illustrated in the figure below. Air rises to flow over mountains. The air cools as The air on this side of the mountain it rises, and water vapor can condense to form contains much less water vapor. As clouds. The clouds can release the water as pre- the air sinks down the side of the cipitation. Therefore, this side of the mountain mountain, it becomes warmer. The tends to be wetter, with more vegetation. warm air absorbs moisture from the land. Therefore, this side of the mountain tends to be drier and more desert-like. TAKE A LOOK 7. Explain Why do clouds form as air moves over a mountain? Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 327 Climate Name Class Date SECTION 1 What Is Climate? continued LARGE WATER BODIES Large bodies of water can affect an area’s climate. Water absorbs and releases heat more slowly than land. This quality helps regulate the air temperature over the land nearby. This is why sudden temperature changes are READING CHECK not very common in areas near large bodies of water. 8. Explain Why aren’t An example of this effect is the climate of Michigan. sudden temperature Michigan is surrounded by the Great Lakes. It has more- changes common near large moderate temperatures than other places at the same bodies of water? latitude. However, the lakes also increase the humidity of the air. This can cause heavy snowfalls in the winter. OCEAN CURRENTS Surface currents can have a big effect on a region’s climate. Surface currents are paths of flowing water found near the surface of the ocean. As surface currents move, they carry warm or cool water to different places. Critical Thinking The temperature of the water affects the temperature of the air above it. For example, warm currents can heat the 9. Describe Processes Cool surface currents can surrounding air. cause the air above them to An example of the effects of ocean currents on climate become cooler. Explain how can be seen in Iceland. Iceland is an island near the Arctic this happens. Circle. The Gulf Stream, a warm surface current, flows past Iceland. The warm water in the Gulf Stream causes Iceland’s climate to be fairly mild. In contrast, the island of Greenland is at a similar latitude but is not affected by the Gulf Stream. Greenland’s climate is much colder than Iceland’s. Arctic Ocean North Europe America North Asia Pacific North Ocean Atlantic Ocean Africa Equator South America Indian Ocean Australia TAKE A LOOK South South Pacific Atlantic 10. Identify What kind Ocean Ocean of surface current is found off the East Coast of the Antarctica United States? Warm current Cold current Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 328 Climate Name Class Date SECTION 1 What Is Climate? continued What Are the Different Climates Around the World? Earth has three major climate zones: tropical, temper- ate, and polar. The figure below shows where these zones are found. Polar 66.5°N Temperate 23.5°N Tropical Earth’s three major climate zones 0° are determined by latitude. Tropical TAKE A LOOK 23.5°S 11. Identify What Temperate determines Earth’s major climate zones? 66.5°S Polar Each climate zone has a certain range of temperatures. The tropical zone, near the equator, has the highest tem- peratures. The polar zones, located at latitudes above 66.5°, have the lowest temperatures. READING CHECK 12. Describe Which BIOMES climate zone has the highest Each climate zone contains several different kinds of temperatures? climates. The different climates are the result of topography, winds, and ocean currents. The different climates affect the organisms that live in an area. A large area with a certain climate and types of organisms is called a biome. READING CHECK 13. Identify Relationships How are biomes and climate related? Equator Polar ice Temperate grassland TAKE A LOOK Tundra Savanna 14.
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