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World Geography Today
Chapter 3
Weather and Climate
Preview
Section 1: Factors Affecting Climate
Section 2: Weather Factors
Section 3: Climate and Vegetation Patterns
Chapter Wrap-Up
World Geography Today
Chapter 3
Section 1: Factors Affecting Climate
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?
World Geography Today
Chapter 3
Section 1: Factors Affecting Climate
Question
By which processes does the Sun interact
with Earth’s atmosphere?
World Geography Today
Chapter 3
Section 1: Factors Affecting Climate
The Sun’s Effect on Earth
The Sun’s energy
reaches Earth.
The other half is
absorbed by Earth’s
surface and
converted into heat
energy.
Half of the energy
is reflected back
into space or
absorbed by the
atmosphere.
The greenhouse
effect helps keep
the planet warm.
The atmosphere traps
this heat in a process
called the greenhouse
effect.
World Geography Today
Chapter 3
Section 1: Factors Affecting Climate
Atmospheric Pressure
• 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.
World Geography Today
Chapter 3
Section 1: Factors Affecting Climate
Global Winds
• 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.
World Geography Today
Chapter 3
Section 1: Factors Affecting Climate
Oceans
• 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.
World Geography Today
Chapter 3
Section 2: Weather Factors
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?
World Geography Today
Chapter 3
Section 2: Weather Factors
Question
What are the steps in the formation of
precipitation, and what are the
four common types of precipitation?
World Geography Today
Chapter 3
Section 2: Weather Factors
Formation of Precipitation
Evaporation
Rain
Humidity
Snow
Condensation
clouds, dew, fog, frost
Sleet
Hail
World Geography Today
Chapter 3
Section 2: Weather Factors
Forms of Precipitation
• 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
World Geography Today
Chapter 3
Section 2: Weather Factors
Question
How do mountains and elevation affect
weather and climate?
World Geography Today
Chapter 3
Section 2: Weather Factors
• 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.
World Geography Today
Chapter 3
Section 2: Weather Factors
Types of Storms
• 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.
World Geography Today
Chapter 3
Section 3: Climate and
Vegetation Patterns
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?
World Geography Today
Chapter 3
Section 3: Climate and
Vegetation Patterns
Question
What are the characteristics of tropical
humid and tropical wet and dry climates?
World Geography Today
Chapter 3
Section 3: Climate and
Vegetation Patterns
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
World Geography Today
Chapter 3
Section 3: Climate and
Vegetation Patterns
Dry Climate Areas
• 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
World Geography Today
Chapter 3
Section 3: Climate and
Vegetation Patterns
Middle-Latitude Climates
• 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
World Geography Today
Chapter 3
Section 3: Climate and
Vegetation Patterns
High-Latitude and Highland 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
World Geography Today
Chapter 3
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?