Download Chapter 3 ppt

World Geography
Ch. 3 Weather & Climate
Earth’s Atmosphere & Climates


The Sun plays the major role in
Earth’s weather and climate.
The four main attributes affecting
climate are:
• the Sun
• Atmospheric pressure
• Wind currents
• The ocean
Global Energy Systems


Temperature – the measurement of
heat energy.
Greenhouse Effect – earth’s
atmosphere allows sunlight to pass
through it, but when the sunlight is
changed into heat energy it is
trapped by the atmosphere, and this
keeps the planet warm.
SECTION 1
Factors Affecting Climate
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.
Air Pressure & Wind






Air Pressure is the force of air around you
extending from the top of the atmosphere that is
constantly pushing on you
Low Pressure Areas –bring unstable weather
conditions.
High Pressure Areas – bring stable, clear, dry
weather.
All low-pressure centers are called cyclones.
Wind – is the horizontal flow of air.
Wind always flows from high to low pressure
areas.
Air Pressure & Wind






Air Pressure is the force of air around you
extending from the top of the atmosphere that is
constantly pushing on you
Low Pressure Areas –bring unstable weather
conditions.
High Pressure Areas – bring stable, clear, dry
weather.
All low-pressure centers are called cyclones.
Wind – is the horizontal flow of air.
Wind always flows from high to low pressure
areas.
4 major air pressure zones
1.
2.
3.
4.
Equatorial low pressure – at the
equator
Subtropical high pressure – equator
to 30° N and equator to 30° S
Subpolar low pressure – 30° N to
60° N & 30° S to 60° S
Polar high pressure – 60° N to
North Pole & 60° S to South Pole
Wind Systems

Prevailing Winds – Winds that usually blow
from the same direction
• Trade Winds –blow from the subtropical high
pressure zone toward the equatorial low
pressure zone. There are NE and SE Trade
Winds.



Doldrums – calm areas with no prevailing
winds along the equator.
Westerlies – West-to-East winds at Middle
Latitudes.
Polar Winds –mainly come from the east
and occur at the poles.
Wind Systems


Front – two air masses with very
different temperatures and amounts
of moisture meet. Fronts usually
cause stormy weather.
Jet Stream – High speed westerly
moving winds in the upper
atmosphere. Not felt directly, but
they move major weather patterns.
Ocean Circulation


Ocean Currents – occur from the
prevailing winds blowing across the
surface of the ocean
El Nino
 El
Nino: The warming of the waters
off the west coast of South America
and is a natural change in the
climate.
 About every 2 – 7yrs the easterly
winds will slow or reverse direction,
changing the ocean temperature and
thus affecting the weather world
wide.
Water & the Atmosphere




Evaporation – process where water is
changed to gas
Humidity – amount of water vapor in
the air
Condensation – process by which
water vapor changes from a gas into
a liquid
Precipitation – Rain (condensed
droplets become large and fall)
SECTION 2
Weather Factors
Formation of Precipitation
evaporation
Condensation
humidity
clouds, dew, fog, frost
rain
snow
sleet
hail
Elevation & Temperature


Orographic Effect – Air comes off the
ocean and hits the mountains. It is forced
to rise and it cools and condensation
begins. This results in rain or snow
Rain Shadow Effect – Deserts form on the
side of the mountain away from the wind,
because areas in the rain shadow do not
receive much rain
Orographic & Rain Shadow Effect
The 12 types of climate regions












Tropical humid
Tropical wet and dry
Arid
Semiarid
Mediterranean
Humid Subtropical
Marine West Coast
Humid Continental
Sub artic
Tundra
Ice Cap
Highland
SECTION
Climate3
and
Vegetation
Patterns
Tropical humid
climate
• close to equator
• warm temperatures,
rainfall all year
• receives Sun’s rays
directly all year
• rising warm, unstable air
• monsoons
Tropical wet and dry
climates
• north and south of
tropical humid
• seasonal change in how
Sun’s rays hit Earth
• alternating wet and dry
seasons
• savannas
Global Warming
Global Warming and to the extent in which
it is occurring is often a topic of
controversy
 However scientists have documented a
rise of 1 degree and suggest that the
increase will reach 3.5 degrees.

Two Different Points of View
Earth’s Natural Warming
and Cooling Cycles


Warming and cooling
cycles
These scientist point
to our past periods of
cold and hot. When
the glaciers advanced
and retreated shaping
our current
landscapes.
Greenhouse effect
 Other scientist argue
that the layer of gases
released from the
burning of coal and
petro traps solar
energy causing higher
temperatures in the
same way a
greenhouse traps
solar energy.