World Geography TodayChapter 3 Weather and Climate Preview Section 1: Factors Affecting...

World Geography Today Chapter 3

Weather and ClimatePreview

Section 1: Factors Affecting Climate

Section 2: Weather Factors

Section 3: Climate and Vegetation Patterns

Chapter Wrap-Up


Read to Discover

• How does the Sun affect Earth’s atmosphere?

• How does atmospheric pressure distribute energy around the globe?

• How do global wind belts affect weather and climate?

• How do the oceans affect weather and climate?



Question

By which processes does the Sun interact with Earth’s atmosphere?



The Sun’s Effect on Earth

The Sun’s energy reaches Earth.

Half of the energy is reflected back

into space or absorbed by the

atmosphere.

The other half is absorbed by Earth’s

surface and converted into heat

energy.

The atmosphere traps this heat in a process called the greenhouse

effect.


The greenhouse effect helps keep the planet warm.


• Low-pressure zones are caused by warm air, which expands and rises.

• High-pressure zones are caused by cold air, which is dense and sinks.

• Pressure differences cause airflow and energy distribution around the globe.

• Warm air moves through the upper atmosphere until the air cools and falls; cold air sinks toward Earth’s surface and then heats up and rises.


Atmospheric Pressure


• Pressure differences cause wind.

• Winds move heat and cold across Earth’s surface.

• Prevailing winds blow from the same direction most of the time, causing similar weather.

• A front occurs when two air masses of widely different temperatures or moisture levels meet.


Global Winds


• Water heats and cools more slowly than land, making coastal areas milder than inland areas.

• Ocean currents move heat between the tropics and polar regions, helping to maintain Earth’s energy balance.


Oceans


Read to Discover

• What are the common forms of precipitation, and how are they formed?

• How do mountains and elevation affect weather and climate?

• What are the different types of storms, and how do they form?



Question

What are the steps in the formation of precipitation, and what are the

four common types of precipitation?



Formation of Precipitation

Rain Snow Sleet Hail

Condensationclouds, dew, fog, frostEvaporation Humidity



• Rain—Liquid formed through condensation of water vapor

• Snow—Ice crystals formed in clouds

• Sleet—Rain that freezes as it falls

• Hail—Chunks of ice formed in storm clouds


Forms of Precipitation


Question

How do mountains and elevation affect weather and climate?



• Increase in elevation causes drop in temperature.

• Mountains cause orographic effect: Moist air meets a barrier and is pushed upward, causing cooling, condensation, and precipitation.

• Mountainside facing wind is the windward, wetter side; side facing away from wind is the leeward, drier side, called the rain shadow.



• Middle-latitude storms form when cold, dry polar air mixes with moist, warm tropical air. Examples include thunderstorms and tornadoes.

• Tropical storms are usually smaller and lack fronts. Examples include hurricanes and typhoons.


Types of Storms


Read to Discover

• How do the two tropical climates differ?

• What conditions are common in dry climates?

• What climates are found in the middle latitudes?

• What characterizes high-latitude and highland climates?



Question

What are the characteristics of tropical humid and tropical wet and dry climates?



Tropical Humid Climate

• Close to equator• Warm temperatures• Rainfall all year• Receives Sun’s rays

directly all year• Rising warm air• Rain forests• Monsoons

Tropical Wet and Dry Climates

• North and south of tropical humid

• Caused by seasonal change in this area

• Alternating wet and dry seasons

• Savannas



• Generally centered about 30 degrees north and south of equator

• Subtropical high-pressure zone causes sinking dry air, with little rain.

• Winters may be very cold, summers very hot.

• Hardy plants and animals


Dry Climate Areas


• Mediterranean—Long, dry summers and mild winters; scrub woodland vegetation

• Humid Subtropical—Hot, humid summers and mild winters; temperate forests

• Marine West Coast—Mild all year; may support dense forests

• Humid Continental—Variable, with four seasons; enough rain to support forests


Middle-Latitude Climates


• Subarctic—Long, cold winters and short, warm summers; vast evergreen forests

• Tundra—Long winters, with permafrost; low shrubs, lichens, mosses, ferns

• Ice Cap—Polar climates; few land plants or animals

• Highland—Varies by elevation, with low elevations relatively mild and high elevations similar to ice cap


High-Latitude and Highland Climates


Chapter Wrap-Up Understanding the Main Ideas

1. How does latitude relate to climate?

2. How do atmospheric pressure zones and ocean currents affect Earth’s energy balance?

3. On a global scale, where is precipitation most common?

4. What effects can hurricanes have on local environments?

5. Where will you find climates that are generally warm and wet all year? What creates dry weather conditions in arid regions?

World Geography TodayChapter 3 Weather and Climate Preview Section 1: Factors Affecting...

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