GLOBAL CLIMATES FOCUS

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1 which you will learn more about in Chapter 6. Refer to the climate map and chart on pages as you read the rest of this chapter. FOCUS GLOBAL CLIMATES What are the major influences on climate? Where are the major global climate regions located? People living in advanced industrial nations such as the United States have used technology to control the effects of climate on their daily lives. Such societies have invested billions of dollars to cool and heat homes and offices, to build water delivery systems for farms and cities, and to construct transportation systems that can operate in good weather and bad. But for four out of every five people on Earth, climate continues to have an immediate impact on every aspect of daily existence. The clothes people wear, the places they live, and the foods they eat all are influenced by climate. The major global climate types are classified mainly by temperature and precipitation differences, both of which are influenced by latitude. That is, latitude has the most control over which regions are hot or cold, wet or dry. To a slightly lesser degree, a region's location on land and its elevation also affect climate. Because the vegetation found in a place is a response to its climate, vegetation is sometimes used to classify climate. Some climate types are named for the dominant vegetation of the region, LOCATION Low-Latitude Climates The areas close to the equator mostly have warm temperatures and a large amount of rainfall yearround. These wet, hot areas have a humid-tropical climate. People who live in the humid tropics never experience winter or even cool weather. Because the equator is constantly being heated by the sun's rays, warm air is always rising in the humid tropics. This continuous rising of warm, unstable air brings almost daily thunderstorms and heavy rainfall. The combination of continuous warm temperatures and heavy rainfall creates ideal conditions for plant growth, and dense tropical rain forests thrive here. In some tropical areas, especially India and Southeast Asia, the rain is concentrated in one very wet season. During- the summer months, moist air flows into these parts of Asia from the warm ocean (high-pressure area) to the hotter land (low-pressure area), bringing heavy rains. During the winter, dry air flows off the cooling continent (high-pressure area) to the warm oceans (low-pressure area), bringing dry conditions to the area. The wind that blows from the same direction for months at a definite season of the year is called a monsoon. Text continues on page 30. Residents of Bombay, India, wade through the high waters caused by the wet monsoon. From where do monsoon winds blow during the wet monsoon season in India?

2 Climates have shaped the world's landscapes and created regions with distinct characteristics. Much of bitterly cold Greenland (above) is covered by an ice cap. A humid-tropical climate nurtures this rain forest in Suriname, South America (upper right). Across the same continent, the Andes Mountains of Peru (right) provide a climate with conditions that vary by elevation. Just to the north and south of the humidtropical climate is the tropical-savanna climate. This wet- and dry-tropical climate is produced by the seasonal change due to the way that the sun's rays strike the areas north and south of the equator. For example, during high-sun season (summer), the sun's rays strike most directly. This high sun increases the temperature and causes low pressure and unstable, rising air that produces heavy rainfall. During the low-sun season (winter), the opposite occurs. As the direct solar rays move to the opposite hemisphere, the subtropical high-pressure zone moves into the area. This causes stable, cool, sinking air and a dry season. BHBfflSB Dry Climates Though their temperatures may vary greatly, all dry climate regions share aridity, or low annual rainfall. The two types of dry climates are the arid desert climate and the semiarid steppe climate. Most of the desert climate areas are centered at about 30 north and south of the equator. The dryness is caused by the subtropical highpressure zone, which brings stable, sinking, dry air all year. Very little rain is produced, and few plants can survive. The largest desert is the Sahara, which stretches across all of northern Africa. As you read earlier, large deserts also form in the rain shadow to the leeward side of mountains. An example is the Great Basin of the United States. Other deserts are far into the interior of continents, away from moisture-bearing winds. These deserts include the Gobi and Taklimakan deserts of Asia, and the deserts of the dry interior of Australia. These desert regions are blocked from rain by mountain ranges and great distances across large continents. They experience temperature extremes ranging from extremely cold temperatures during winter to hot, scorching temperatures during summer. Small and very dry deserts are found along the west coasts of continents. Here, the cool ocean currents cause stable conditions, and it may not rain for many years. Examples of dry coastal deserts are found along the west coasts of South America, southwestern Africa, and Mexico. The semiarid steppe climate is a transition area between the arid deserts and the more humid climates. The term steppe refers to shortgrass vegetation. Areas with steppe climates

3 receive more moisture than the deserts but less than the more humid areas. Steppe climates generally support grasslands, and trees are rare except along river banks. Today, the natural grasslands in many places have been replaced with fields of food grains. Poor farming practices and overgrazing have turned some natural grasslands into human-made deserts. LOCATION Middle-Latitude Climates As is the case with low-latitude climates, there are several types of middle-latitude climates. Located between 30 and 40 latitude, the Mediterranean climate is confined mainly to the coastal areas of southern Europe and the west coasts of continents with cool ocean currents. Mediterranean climates usually do not extend far inland beyond mountain ranges. The stable, sinking air of the subtropical high-pressure zone causes long, sunny, dry summers. During the mild winter, however, cool middle-latitude storms enter the region with the westerlies and bring needed rains. The humid-subtropical climate is much more widespread than the Mediterranean climate. This climate is found on the eastern side of continents with warm ocean currents. The humid-subtropical climate is greatly affected by moist air flowing off the warm ocean waters. Summers are hot and humid. Winters are mild, with occasional frost and some snow. The warm ocean currents cause areas with the humid-subtropical climate to be struck by occasional hurricanes or typhoons. A climate type influenced mainly by oceans is called the marine-west-coast climate. This climate is generally found on the west coasts of continents in the upper middle latitudes. Temperatures are mild all year. Middle-latitude storms traveling across the oceans in the westerlies bring most of the rainfall to areas with this climate. Winters are foggy, cloudy, and rainy, but summers can be warm and sunny. This climate supports dense evergreen forests in the Northwest United States. The marine-west-coast climate is most widespread in northwestern Europe where the absence of mountain ranges along the coast allows the cool, moist ocean air to spread far into the interior of the continent. The humid-continental climate is found in latitudes that are subject to periodic invasions of both warm and cold air. This climate has the most changeable weather conditions and experiences four distinct seasons. Its midcontinental locations are responsible for extreme differences between summer and winter temperatures. Because this climate type is situated along the polar front, middle-latitude storms bring rain throughout much of the year and bring snow in winter. Precipitation is heavy enough to support forests. Chapter3 31

4 LOCATION High-Latitude Climates Located in the high latitudes, the subarctic climate is centered above 0 north latitude. This climate has long, dark, cold winters, with temperatures staying well below freezing for half of the year. During the short summers, however, very warm temperatures can occur. The subarctic climate has the greatest annual temperature ranges in the world. Though severe, the subarctic climate supports vast evergreen forests. The subarctic climate region is very large, extending across northern North America, Europe, and Asia. The Southern Hemisphere lacks this climate type because there is no land at these latitudes. Another climate with a long winter is the tundra climate. Temperatures are above freezing only during the short summers. The tundra climate takes its name from the only vegetation that can survive there. Tundra vegetation is made up of small, hardy plants such as mosses, lichens (LIEkuhnz), herbs, and low shrubs. The climate is so severe that no trees grow. Water below the tundra surface remains frozen throughout the year. This condition is called permafrost. Although the melting winter snow creates swamps and bogs on the surface during the summer, permafrost makes it difficult for the water to seep into the ground. These wet areas do, however, support great numbers of insects and birds during the short summer. The polar ice-cap climate has cold temperatures all year, and snowfall is likely year-round. Life is almost impossible in polar ice-cap climates. Only animals and plants that can live in the icy polar seas survive here. LOCATION Highland Climates As you learned earlier, an increase in elevation causes a decrease in temperature. Highland climates are determined by elevation rather than by latitude. Mountain areas of the world can have a variety of climate types in a very small area. The lowest elevations of a mountain will have a climate and vegetation similar to that of the surrounding area. As you climb higher up the mountain, the climate conditions change. Temperatures and air pressure are lower. The cooler temperatures limit the vegetation that can grow, especially trees. At the highest elevations, climate conditions are similar to those of the polar ice-cap climate. Here, temperatures remain below freezing, and ice and snow are always present. SECTION REVIEW 1. How does the latitude of a place influence its climate? 2. Give an example of a climate type found in each of the following climate regions: low-latitude, dry, middle-latitude, and high-latitude. 3. Critical Thinking Compare and contrast desert climates and tundra climates. 32 Unit 1

5 (A <U a ) l/> Q S 0) o o Climate HUMID TROPICAL TROPICAL SAVANNA DESERT STEPPE.^B MEDITERRANEAN HUMID SUBTROPICAL Geographic Distribution along Equator; particularly equatorial South America, Zaire Basin in Africa, Southeast Asia between humid tropics and deserts; tropical regions of Africa, South and Central America, southern and Southeast Asia, Australia centered along 30 latitude; some middlelatitude deserts in interior of large continents and along western coasts; particularly Saharan Africa, southwest Asia, central and western Australia, southwestern North America generally bordering deserts and interiors of large continents; particularly northern and southern Africa, interior western North America, central and interior Asia and Australia, southern South America west coasts in middle latitudes; particularly southern Europe, part of southwest Asia, northwestern Africa, California, southwestern Australia, central Chile, southwestern South Africa east coasts in middle latitudes; particularly southeastern United States, eastern Asia, central southern Europe, southeastern parts of South America, South Africa, and Australia Major Weather Patterns warm and rainy year-round, with rain totaling anywhere from 6 to more than 40 in. (16-1,143 cm) annually; typical temperatures are 90-9 F (32-3 < 'C) during the day and 6-70"F (18-21''C) at night warm all year; distinct rainy and dry seasons; precipitation during the summer of at least 20 in. (1 cm) and in some locations exceeding 10 in. (380 cm); summer temperatures average 90 F (32 C) during the day and 70 F (21 C) at night; typical winter temperatures are 7-80 F (24-27 C) during the day and -60 F (13-16 C) at night arid; precipitation of less than 10 in. (2 cm) annually; sunny and hot in the tropics and sunny with great temperature ranges in middle latitudes; typical summer temperatures for lower-latitude deserts are F (43-46 C) during the day and 60-6 F (16-18 C) at night, while winter temperatures average 80 F (27 C) during the day and 4 F (7 C) at night; in middle latitudes, the hottest month averages 70 F (24 C) semiarid; about in. (2-1 cm) of precipitation annually; hot summers and cooler winters with wide temperature ranges similar to desert temperatures dry, sunny, warm summers and mild, wetter winters; precipitation averages 1-20 in. (38-1 cm) annually; typical temperatures are 7-80 F (24-27 C) on summer days; the average winter temperature is0 F(10 C) hot, humid summers and mild, humid winters; precipitation year-round; coastal areas are in the paths of hurricanes and typhoons; precipitation averages 40 in. (102 cm) annually; typical temperatures are 7-90 F (24-32 C) in summer and 4-0 F (7-10 C) in winter Vegetation tropical rain forest tropical grassland with scattered trees sparse droughtresistant plants; many barren, rocky, or sandy areas grassland; few trees scrub woodland and grassland mixed forest s -0 3 TO <U O D Climate MARINE WEST COAST HUMID CONTINENTAL Geographic Distribution west coasts in upper-middle latitudes; particularly northwestern Europe and North America, southwestern South America, central southern South Africa, southeastern Australia, New Zealand east coasts and interiors of upper-middlelatitude continents; particularly northeastern North America, northern and eastern Europe, northeastern Asia Major Weather Patterns cloudy, mild summers and cool, rainy winters; strong ocean influence; precipitation averages in. (1-12 cm) annually, with some coastal mountains receiving more than 200 in. (08 cm); average temperature in hottest month usually is between 60 F and 70 F (16-21 C); average temperature in coolest month usually is above 32 F (0 C) four distinct seasons; long, cold winters and short, warm summers; precipitation amounts vary, usually 20-0 in. or more (1-127 cm) annually; average summer temperature is 7 F (24 C); average winter temperature is below freezing Vegetation temperate evergreen forest mixed forest VI VI SUBARCTIC higher latitudes of interior and east coasts of continents; particularly northern parts of North America, Europe, and Asia extremes of temperature; long, cold winters and short, warm summers; low precipitation amounts all year; precipitation averages -1 in. (13-38 cm) in summer; temperatures in warmest month average 60 F (16 C), but can warm to 90 F (32 C); winter temperatures average below 0 F(-18''C) northern evergreen forest 3 re i.c 01 X TUNDRA ICECAP high-latitude coasts; particularly far northern parts of North America, Europe, and Asia, Antarctic Peninsula, subantarctic islands polar regions; particularly Antarctica, Greenland, Arctic Basin islands cold all year; very long, cold winters and very short, cool summers; low precipitation amounts; precipitation average is -1 in. (13-38 cm) annually; warmest month averages 40"F (4 C); coolest month averages a little below 0 F(-18 C) freezing cold; snow and ice year-round; precipitation averages less than 10 in. (2 cm) annually; average temperatures in warmest month are not higher than freezing moss, lichens, low shrubs; permafrost bogs in summer no vegetation HIGHLAND 'SSSSBSSSSSfSk high mountain regions, particularly western parts of North and South America, eastern parts of Asia and Africa, southern and central Europe and Asia i greatly varied temperatures and precipitation amounts over short distances as elevation changes forest to tundra vegetation, depending on elevation

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