UNIT THREE: Matter, Energy, and
Earth
 Chapter 8 Matter and Temperature
 Chapter 9 Heat
 Chapter 10 Properties of Matter
 Chapter 11 Earth’s Atmosphere and
Weather
Chapter Eleven: Earth’s Atmosphere
and Weather
 11.1 Earth’s Atmosphere
 11.2 Weather Variables
 11.3 Weather Patterns
11.2 Learning Goals
 Explain the causes of weather.
 Discuss the role of convection in moving air
through Earth’ s atmosphere.
 Describe the characteristics of Earth’s major
climate regions.
Investigation 11B
Observing the Weather
 Key Question
 How can you use weather data to make
predictions?
11.2 Weather Variables

Weather is a term that
describes the condition
of the atmosphere in
terms of temperature,
wind, and atmospheric
pressure.

There are many
conditions on earth
that affect how and why
weather changes.
11.2 Convection, pressure, and wind
 Convection occurs
naturally in Earth’s
atmosphere due to
the heating and
cooling of air.
 A thermal is a small,
upward flow of warm
air caused by
convection.
Gliding birds like hawks often
ride a thermal as they hunt.
11.2 Convection

Heated air near a hot
surface is less dense than
the colder air above it.

The heated air rises,
forcing the colder air to
move aside and sink
toward the ground.

Then this colder air is
warmed by the surface,
and it rises.

Wind is created.
11.2 Wind
 An air mass is a large body of air with
consistent temperature and moisture
content throughout.
 Wind is the horizontal movement of air
that occurs as a result of a pressure
difference between two air masses.
11.2 Convection in the atmosphere
 Convection near coastlines causes
sea breezes during the day and land
breezes at night.
11.2 Global Convection
 The combination of
global convection
and Earth’s rotation
sets up a series of
wind patterns called
convection cells.
11.2 Global patterns

Three important global
wind patterns exist in
each hemisphere:
 Trade winds
 Prevailing westerlies
 Polar easterlies
11.2 Coriolis effect
 The bending of currents of air due to the Earth’s
rotation is called the Coriolis effect.
11.2 Polar fronts
 At a boundary called
the polar front, the
dense, polar air forces
the warmer, westerly air
upward.
 During the winter, polar
fronts slide toward the
equator and during the
summer they retreat
northward.
11.2 Air and water vapor

Water in gas form is called
water vapor.

Like a soggy sponge, air
reaches a point and can’t
hold anymore vapor.

The vapor turns back into
liquid and form droplets.
Use these pictures to explain
how the cycle can continue.
11.2 Precipitation
 Rain is the result of a
cooling air mass.
 Cooling an air mass is
like wringing out a wet
sponge.
 Tiny droplets form a
cloud or fog.
 Larger droplets fall as
rain.
11.2 Precipitation
 Tiny water droplets
are suspended in the
atmosphere.
 Whether the particles
are liquid water or
water vapor depends
changes in pressure
and temperature.
11.2 Precipitation
 When the rate of
evaporation is
greater than the rate
of condensation, we
see clearing skies.
 When the rate of
condensation
exceeds the rate of
evaporation, it rains.
11.2 Snow
 Snow usually forms
when both ice crystals
and water droplets are
present in the sky.
 The water droplets
attach to ice crystals
and freeze.
 When the ice crystals
are large enough, they
will fall to the ground.
11.2 Relative Humidity
 Relative humidity is a measure of how much
water vapor an air mass contains.
11.2 Climate and biomes
 Climate is the type of
weather that a place
has, on average, over a
long period of time.
 Climate depends on
many factors:





latitude,
precipitation,
elevation,
topography, and
distance from large
bodies of water.
11.2 Climate and biomes
 Scientists divide the planet into climate
regions called biomes.
 Earth has six main biomes: deserts,
grasslands, temperate deciduous
forests, rainforests, taiga, and tundras.
 Each biome has a unique set of plants
and animals that thrive in its climate.
11.2 Climate and biomes
 The Serengeti is a home to thousands of
predators species and 1.6 million herbivores.
11.2 Climate and biomes
 Humidity is related to
plant and animal
diversity.
 From the poles to the
equator, humidity and
the diversity of plants
and animal increases.
11.2 Biomes and temperature
 At the equator, sunlight
is direct and intense.
 As a result, the
average yearly
temperature at the
equator is 27 °C (80 °F),
while at the North Pole
it is -18 °C (0 °F).
11.2 Biomes and elevation
 Elevation is
another
important factor
in determining
the type of
biome.
11.2 Biomes and temperature
 Compare the data below for Portland, OR and
Minneapolis, MN.
 If these cities are about the same latitude, why
don’t they have the same climate?
11.2 Biomes and temperature
 The differences in
temperature between the
two cities have to do
with water.
 Water warms up and
cools down slowly.
 Regions near water—like Portland, OR—do
not have extremely hot or cold weather, even
though they are farther north.
11.2 Plants and animals in biomes
 A biome consists of
plant and animal
communities.
 The plants and
animals in a
community survive in
a shared environment.
11.2 Plants and animals in biomes
 Within a biome, there are
many interrelated
ecosystems.
 An ecosystem is made up
of the plants and animals
that live there, plus
nonliving things like soil,
air, water, sunlight, and
nutrients.
11.2 Plants and animals in biomes
 What features of this
jackrabbit help it
survive in it’s desert
biome?