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Weather and Climate
Chapter 24 -- pg. 744-787
Chapter 24.1
 Key Terms:
 Atmosphere
 Air pressure
 Barometer
 Troposphere
 Weather
 Stratosphere
 Ozone layer
 Mesosphere
 Thermosphere
 Ionosphere
 Aurora
The Atmosphere
24.1 Key Concepts
 How does the atmosphere affect conditions
on Earth?
 What is Earth’s atmosphere composed of?
 How do pressure and density vary with
altitude?
 What are the characteristics of the major
layers of the atmosphere?
24.1 The Atmosphere
 The study of the atmosphere is called Meteorology.
 The study of meteorology also covers the study of
weather and climate.

Weather is the general condition of the
atmosphere at a particular time and place.

Climate is the general weather conditions over a
period of years.
24.1 The Atmosphere
 Atmosphere: A layer of
gas that surrounds Earth
 The atmosphere forms a
protective boundary
between Earth and space
and provides conditions
that are suitable for life
24.1 The Atmosphere
 The atmosphere holds in heat
and helps regulate
temperatures that are suitable
for life.
 The two most prevalent
substances in our atmosphere
are carbon dioxide and water
vapor (both are waste products
we exhale).
24.1 The Atmosphere
 Air Pressure: the force exerted
by the weight of a column of air
on a surface.
 This weight is a result of
gravity
 Air pressure changes with
altitude.
 Is most dense near surface and
less dense as altitude rises.
 As altitude increases, air
pressure and density decreases
24.1 The Atmosphere
 Barometer: an
instrument used to
measure air pressure.
 As air pressure
increases, mercury in
the column rises.
 As air pressure
decreases, mercury in
the column falls.
24.1 The Atmosphere

Layers of The Atmosphere:
1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere
5. Ionosphere
24.1 The Atmosphere
 Troposphere: lowest layer
 Contains almost all
atmosphere’s water vapor
 Most weather takes place
here
 Average height is 12 km
24.1 The Atmosphere
 Stratosphere: 2nd
layer of atmosphere
 12-50 km is height
 Layer in which ozone
is present

Absorbs UV radiation
which is harmful to
life
 Layer in which planes
and weather balloons
travel
24.1 The Atmosphere
 Mesosphere: 3rd layer
of atmosphere
 50-80 km in height
 At top of mesosphere
temps reach -90
 Air moves 320 km/hr
 Meteoroids that enter
the atmosphere burn
up here
24.1 The Atmosphere
 Thermosphere:
outermost layer of the
atmosphere
 80-? Km

no boundaries
marks end of
atmosphere
24.1 The Atmosphere
 Ionosphere: not a distinct
layer
 Region of charged particles,
or ions, that overlaps the
lower thermosphere
 Aurora: a colorful display of
light in the sky
 Ions become attracted to
magnetic poles of Earth and
start to glow. EXAMPLE:
Northern Lights
24.2 The Sun and the Seasons
 Key terms:







Rotation
Revolution
Tropic zone
Temperate zones
Polar zones
Solstice
Equinox
24.2 Key Concepts
 What are two ways in which Earth moves?
 Who is Earth’s surface divided into zones
based on latitude?
 What causes the seasons?
24.2 The Sun and the Seasons
 The Earth moves in two different
ways
 Rotation: the spinning of Earth
on its axis
 Causes day and night
 24 hours for Earth to make
one rotation
 Revolution: the movement of
one body around another
 Earth revolves around the
sun
 Takes 365.25 days for Earth
to make one revolution
24.2 The Sun and the Seasons
 Latitude Zones: three regions within which
the temperatures are generally the same



Tropic zone
Temperate zone
Polar zone
24.2 The Sun and the Seasons
 Seasons: caused by the
tilt of Earth’s axis as it
moves around the sun
 23.5 degree tilt
 Summer
 Fall
 Winter
 Spring
24.2 The Sun and the Seasons
 Solstices: occurs on the two days a year when the sun is
directly overhead
 Northern hemisphere:
 Summer solstice  June 21st


Longest day of the year
Winter solstice  December 21st
 Shortest day of the year
24.2 The Sun and the Seasons
 Equinox: neither hemisphere is tilted towards the
sun, the length of both day and night are
approximately equal.
 Northern Hemisphere

Vernal equinox  March 21st

Autumnal equinox  September 21st
24.3 Solar Energy and Winds
 Key terms:
 Greenhouse effect
 Wind
 Local wind
 Sea breeze
 Land breeze
 Global winds
 Coriolis effect
 Monsoon
 Jet stream
24.3 Key Concepts
 What happens to the energy the Earth
receives from the sun?
 How is energy transferred within the
troposphere?
 What causes winds?
 What are some examples of local winds and
global winds?
24.3 The Sun and the Seasons
 Some solar energy that
reaches Earth’s atmosphere is
reflected back, some is
absorbed by the atmosphere,
and some is absorbed by
Earth’s surface.




50% absorbed by surface
25% reflected by clouds, dust,
and gases
20% absorbed by clouds and
gases
5% reflected by surface
24.3 The Sun and the Seasons
 Greenhouse effect: Gases in the atmosphere
releases absorbed energy to the Earth’s surface
 Energy is transferred in three ways:



Radiation
Conduction
Convection
24.3 The Sun and the Seasons
 Wind: horizontal movement of air

Caused by differences in air pressure
 Caused by unequal heating of Earth’s surface
 Naturally flows from areas of high pressure to areas
of low pressure.
 As air is heated it expands and becomes less dense
and rises. Cool air flows to replace it thus creating
wind.
24.3 The Sun and the Seasons
 Local Winds: The breezes that occur where land meets a large body
of water are examples of local winds.
 Water has a higher specific heat than land.
 The sun heats and cools the land quicker than the water.
 The air above the land heats quicker than the air above the water

During the day:
 The warmer air above the water will expand and rise,
creating a low pressure area above the water.
 The cooler air above the land flows to replace it.

During the night:
 The warmer air above the water will expand and rise,
creating a low pressure area above the water.
 The cooler air above the land flows to replace it.
24.3 The Sun and the Seasons
 Sea Breeze: The cooler air over
the water flows towards land

Occurs during the day time
 Land Breeze: The cooler over
land flows towards the water

Occurs during the night time
24.3 The Sun and the Seasons
 Global winds: Winds that blow over long
distances from a specific direction
24.3 The Sun and the Seasons
 Convection Cells: global
winds move in a series of
huge bands
 If Earth wasn’t rotating on
its axis winds would flow
in straight lines.
24.3 The Sun and the Seasons
 Coriolis Effect: the curving
effect the Earth’s rotation
has on all free-moving
objects.
 If the United States shoots a
rocket towards the north
pole it will travel exactly in a
straight line. It’s the Earth’s
rotation underneath the
rocket that gives it the
illusion of curving.
24.3 The Sun and the Seasons
 Monsoon: a wind system that is
characterized by seasonal
reversal of direction
 Extreme land and sea breeze

Summer monsoon:
 Brings cool temperatures
and heavy rain

Winter monsoon:
 Brings very hot and dry
weather
24.3 The Sun and the Seasons
 Jet stream: a belt of high-speed wind in the upper
troposphere
 Develop at high altitudes by great differences in air
pressure.
24.4 Water in the Atmosphere
 Humidity: the amount of
water vapor in the air.
 Relative Humidity: is
expressed in %.

40% humidity means
the air contains 40%
water vapor.
24.4 Water in the Atmosphere
 Clouds form as warm, moist air rises and
water vapor condenses in the atmosphere.
 Types of clouds:

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Stratus
Cumulus
Cirrus
24.4 Water in the Atmosphere
 Stratus: flat layers of
clouds that cover much
or all of the sky.
 Meaning: “Spread
out”
 When Nimbo or Nimbus
is added to cloud’s
name, it means that the
cloud produces
precipitation.
 EXAMPLE: Nimbostratus
24.4 Water in the Atmosphere
 Cumulus: puffy white clouds that look like
piles of cotton balls with flat bottoms.

Meaning: “Heap”
24.4 Water in the Atmosphere
 Cirrus: Thin, white, wispy clouds, often with a
feathery or veil-like appearance.

Often blow into an area ahead of rain-producing
clouds.
24.4 Water in the Atmosphere
 Forms of precipitation:
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Rain
Snow
Hail
Sleet
Freezing Rain
24.5 Weather Patterns
 Air Mass: forms when a large body of air
becomes fairly stationary over a region of
Earth’s surface or as air moves over a large,
uniform region like an ocean.
24.5 Weather Patterns
 Fronts: a defined boundary that forms when
two unlike air masses meet.

4 types of fronts:

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Cold
Warm
Stationary
Occluded
24.5 Weather Patterns
 Cold front: occurs when a cold air mass overtakes a
warm air mass.
 Cumulus or cumulonimbus clouds are often
produced. Causing severe wind and
thunderstorms
24.5 Weather Patterns
 Warm fronts: occurs when a warm air mass
overtakes a cold air mass.
 Usually produces stratus or nimbostratus clouds
and a heavy steady rain.
24.5 Weather Patterns
 Stationary front: two unlike air masses have
formed a boundary but neither is moving.
24.5 Weather Patterns
 Occluded front: occurs when a warm air mass is caught
between two cold air masses
 A rare front that forces the warm air mass up, cutting it off from
the ground and trapping it between two cold air masses.
 Causes cloudy days and some precipitation.