HOLT World Geography Today CHAPTER 3 Weather and

HOLT World Geography Today CHAPTER 3 Weather and Climate Section 1: Factors Affecting Climate Section 2: Weather Factors Section 3: Climate and Vegetation Patterns 1 HOLT, RINEHART AND WINSTON

Section 1 Factors Affecting Climate HOLT World Geography Today Objectives: n How does the Sun affect Earth’s atmosphere? n How does atmospheric pressure distribute energy around the globe? n How do global wind belts affect weather and climate? n How do the oceans affect weather and climate? 2 HOLT, RINEHART AND WINSTON

Section 1 Factors Affecting Climate HOLT World Geography Today Effect of the Sun on Earth’s atmosphere: n Some solar energy, in the form of heat, reflects off Earth back into the atmosphere. n Atmosphere traps this heat energy in a process called the greenhouse effect. n Process helps keep the planet warm. 3 HOLT, RINEHART AND WINSTON

Section 1 Factors Affecting Climate HOLT World Geography Today Atmospheric pressure and energy distribution: n Low-pressure zones are caused by warm air, which expands and rises. n High-pressure zones are caused by cold air, which is dense and sinks. n Pressure differences cause air flow and energy distribution around the globe. n Warm air moves through the upper atmosphere until it cools and falls; cold air moves along Earth’s surface until it heats up and rises. 4 HOLT, RINEHART AND WINSTON

Section 1 Factors Affecting Climate HOLT World Geography Today Global winds affect weather and climate: n Pressure differences cause wind. n Winds move heat and cold across the Earth’s surface. n Prevailing winds blow from the same direction most of the time, causing similar weather. n A front occurs when two air masses of widely different temperatures or moisture levels meet. 5 HOLT, RINEHART AND WINSTON

Section 1 Factors Affecting Climate HOLT World Geography Today Oceans affect weather and climate: n Water heats and cools more slowly than land, making coastal areas milder than inland areas. n Ocean currents move heat between the tropics and polar regions, helping to maintain Earth’s energy balance. 6 HOLT, RINEHART AND WINSTON

Section 2 Weather Factors HOLT World Geography Today Objectives: n What are the common forms of precipitation, and how are they formed? n How do mountains and elevation affect weather and climate? n What are the different types of storms, and how do they form? 7 HOLT, RINEHART AND WINSTON

Section 2 Weather Factors HOLT World Geography Today Forms of precipitation: n rain—liquid formed through condensation of water vapor n snow—ice crystals formed in clouds n sleet—rain that freezes as it falls n hail—chunks of ice formed in storm clouds 8 HOLT, RINEHART AND WINSTON

Section 2 Weather Factors HOLT World Geography Today Effects of mountains and elevation on weather and climate: n Increase in elevation causes drop in temperature. n Mountains cause orographic effect: moist air meets a barrier and is pushed upward, causing cooling, condensation, and precipitation. n Mountainside facing wind is the windward, wetter side; side facing away from wind is the leeward, drier side, called the rain shadow. 9 HOLT, RINEHART AND WINSTON

Section 2 Weather Factors HOLT World Geography Today Types of storms: n Middle-latitude storms form when cold dry polar air mixes with moist warm tropical air. Examples include thunderstorms and tornadoes. n Tropical storms are usually smaller and lack fronts. Examples include hurricanes and typhoons. 10 HOLT, RINEHART AND WINSTON

Section 3 Climate and Vegetation Patterns HOLT World Geography Today Objectives: n How do the two tropical climates differ? n What conditions are common in dry climates? n What climates are found in the middle latitudes? n What characterizes high-latitude and highland climates? 11 HOLT, RINEHART AND WINSTON

Section 3 Climate and Vegetation Patterns HOLT World Geography Today Differences in the two tropical climates: n Tropical humid climate n close to equator n generally warm and wet year-round n climate supports dense rain forests n Tropical wet and dry climate n farther from equator; north and south of the tropical humid zone n warm wet season alternates with cooler, drier season n seasonal variation supports savannas: tropical grasslands with scattered trees and shrubs 12 HOLT, RINEHART AND WINSTON

Section 3 Climate and Vegetation Patterns HOLT World Geography Today Dry climate areas: n generally centered about 30 degrees north and south of equator n subtropical high-pressure zone causes sinking dry air, with little rain n winters may be cold, summers very hot n hardy plants and animals 13 HOLT, RINEHART AND WINSTON

Section 3 Climate and Vegetation Patterns HOLT World Geography Today Middle-latitude climates: n Mediterranean—long, dry summers and mild winters; scrub woodland vegetation n humid subtropical—hot, humid summers and mild winters; temperate forests n marine west coast—mild year-round; may support dense forests n humid continental—variable, with four seasons; enough rain to support forests 14 HOLT, RINEHART AND WINSTON

Section 3 Climate and Vegetation Patterns HOLT World Geography Today High-latitude and highland climates: n subarctic—long cold winters and short warm summers; vast evergreen forests n tundra—long winters, with permafrost; low vegetation n ice cap—polar climates, with few plants or land animals n highland—climate varies by elevation, with low elevations relatively mild and high elevations similar to ice cap 15 HOLT, RINEHART AND WINSTON