Chapter 3

Climates of Earth

Weather and Climate• Weather - changes in air that take place

over a short period of time.

• Climate - the usual, predictable pattern of weather in an area over a long period of time.

• Climate is affected by the sun, wind, water, landforms, and even people.

• To understand an area’s climate, scientists look at extremes of temperature and precipitation.

The Sun and Climate• The MAIN source of climate is the sun. • Climate is affected by latitude, which

affects the angle of the sun’s rays.

• Areas near the Equator are called the tropics. They lie between the Tropic of Cancer (23½°N latitude) and the Tropic of Capricorn (23½°S latitude).

• The sun’s rays are more direct here, so it is hotter.

Latitude Zones

The Wind’s Effect on Climate• Moving air is called wind.

• Wind is caused by the rising of warm air.

• Winds follow typical patterns, which affect climate.

Prevailing Winds

The Wind’s Effect on Climate• Monsoons are seasonal winds that blow

over regions for months at a time. They are found mainly in Asia and some areas in Africa.

The Wind’s Effect on Climate

• Local winds are patterns of wind caused by landforms in a particular area. Some local winds occur because land warms and cools more quickly than water.

• As a result, cool sea breezes keep coastal areas cool during the day. After the sun sets, land cools down, and land breezes blow out to sea.

The Wind’s Effect on Climate

The Wind’s Effect on Climate

The Wind’s Effect on Climate

The Wind’s Effect on Climate• Thunderstorms sometimes produce

tornadoes, or funnel-shaped windstorms.

• The United States experiences more tornadoes than any other country.

The Wind’s Effect on Climate

TORNADO ALLEY

Campbelltown, PA – July, 2004

The Wind’s Effect on Climate (cont.)

• Violent tropical storms, hurricanes, form over the warm waters of the Atlantic Ocean in summer and early fall.

• Hurricanes often strike the Caribbean Sea and North America. The same type of storm in Asia is called a typhoon.

The Wind’s Effect on Climate (cont.)

(pages 56–57)

The Wind’s Effect on Climate (cont.)

• A long period of extended dryness is called a drought. Droughts are caused by unusual weather patterns.

• A unique combination of temperature, wind, and water effects in the Pacific Ocean is called El Niño.

• El Niños occur about every three years when cold winds from the east are weak and the Pacific Ocean gets warmer than usual.

• When those winds are unusually strong, it is known as La Niña.

The Wind’s Effect on Climate (cont.)

Ocean and Currents• Oceans affect temperatures and rainfall.

• Moving streams of water called currents carry warm or cool water around the world’s oceans.

• Currents affect the climate of nearby land areas. Winds that blow over currents carry their temperatures to the land.

Ocean and Currents

San Francisco - 1989

Climate and Landforms• The higher the elevation a place has, the

cooler it will be.

• As air moves over mountain peaks, it can create a rain shadow.

Climate and Landforms

Climate and Landforms

The Impact of People on Climate

• People’s actions affect climate.

• Cities are warmer than rural areas.

• Streets and buildings absorb more heat than plants and trees do.

• Evaporation from plants has cooling effect.

The Impact of People on Climate

The Impact of People on Climate (cont.)

• The buildup of greenhouse gases prevents heat from rising and escaping into space.

• People burn fuels, which causes global warming due to the greenhouse effect.

The Impact of People on Climate (cont.)

The Impact of People on Climate (cont.)

The Impact of People on Climate (cont.)

The Impact of People on Climate (cont.)

• Dense forests that receive high amounts of rain each year are known as rain forests.

• People burn trees to clear rain forests, which releases greenhouse gases. Also, less water evaporates if there are fewer trees, decreasing rainfall and preventing growth.

(pages 56–57)

The Impact of People on Climate (cont.)

Climate Zones

• Geographers divide the world into 12 different climate zones.

• They are divided into 5 major categories.

1. Tropical

2. Mid-Latitude

3. High Latitude

4. Dry

5. Highland

Tropical Climates• There are two tropical climates – tropical

rain forest and tropical savanna. • Tropical rain forest - year-round rains

that produce thick rain forests. Tall hardwood trees such as mahogany, teak, and ebony form a canopy, or top layer of the forest.

Canopy

(page 64)

Tropical Climates

Tropical Rain forestHot and Wet all year

Tropical Climates

• Tropical savanna - hot, wet season and hot, dry season. Broad grasslands with few trees, called savannas, are found here.

Tropical savanna

(page 64)

Tropical Climates

Tropical savannaHot all year – wet and dry seasons

Tropical Climates (cont.)

Mid-Latitude Climates• Created by a mix of air masses: warm air

from the tropics and cool air from the polar regions.

• Marine west coast climate - along coastal areas that receive winds from the ocean.

• Winters - mild and rainySummers - wet and warmDeciduous trees and temperate rain forests grow here.

Temperate rain forest

Mid-Latitude Climates

Marine west coastwet with moderate temperatures

Tropical Climates (cont.)

Mid-Latitude Climates (cont.)

• Mediterranean climate also has rainy, mild winters but hot, dry summers. Shrubs and short trees grow in this climate.

• Humid continental climate - inland areas of North America, Europe, and Asia.

• Winters - long, cold, and snowySummers - short and very hot. Deciduous trees and grasslands grow here.

Mid-Latitude Climates (cont.)

MediterraneanHot dry summer, mild wet winter

Tropical Climates (cont.)

Mid-Latitude Climates (cont.)

Humid continentalwet – hot summer, cold winter

Tropical Climates (cont.)

• Mid-latitude regions close to the tropics experience a humid subtropical climate - hot, wet summers and mild winters. Oak, magnolia, and palm trees grow here.

Mid-Latitude Climates (cont.)

Mid-Latitude Climates (cont.)

Humid subtropicalMoist – hot summer, mild winter

Tropical Climates (cont.)

High Latitude Climates• In the high latitudes nearest the mid-

latitude zones, you will find the subarctic climate.

• Winters are severely cold and bitter. Huge evergreen forests called taiga grow here.

Taiga

High Latitude Climates

High Latitude Climates

SubarcticLong winter, short mild summer

High Latitude Climates

• Closer to the Poles lie areas of vast rolling plains without trees.

• This region is known as the tundra and is harsh and dry.

• In tundras, much of the lower layers of soil stay permanently frozen and are known as permafrost.

• Only sturdy grasses and low bushes grow here.

Tundra Vegetation

Tundra

High Latitude Climates

Tundra – cold, dry, permafrost

High Latitude Climates (cont.)

• Ice cap climate is found at the Poles and on the ice sheets of Antarctica and Greenland.

• No vegetation grows here; only lichens can live on the rocks.

High Latitude Climates (cont.)

Ice cap – always frozen

Tropical Climates (cont.)

Dry Climates

• Desert climates - the driest climates - get less than 10 inches of rainfall a year. Only scattered plants like cacti can live here.

Tropical Desert

Tropical Desert

Desert – less than 10 inches a year

Mid-latitude Desert

Mid-latitude Desert

DesertLess than 10 inches rain a year

Dry Climates• Many deserts are surrounded by partly dry

grasslands known as steppes. The Great Plains of the United States has a steppe climate, which averages 10 to 20 inches of rain a year.

Steppe Vegetation

Dry Climates

Steppe10-20 inches per year

Tropical Climates (cont.)

Highland Climates• Mountains tend to have cool climates -

even near the Equator. • A highland, or mountain, climate has cool

or cold temperatures throughout the year. No trees grow above the timberline.

Highland Climates

Alpine Tundra - Timberline

Tropical Climates (cont.)