Download Global and Local Weather Patterns

Global and Local Weather Patterns
The Earth is heated by the energy
from the sun.
1. Radiation – the transfer of energy as electromagnetic waves. (The
sun’s energy travels through space.)
2. Conduction – the transfer of thermal energy by direct contact.
(Walking barefoot on a hot sidewalk.)
3. Convection – transfer of thermal energy by the circulation or
movement of a liquid of gas. (Hot air rises and cool air sinks.)
The GREENHOUSE EFFECT is the Earth’s
heating process in which gases in the
atmosphere trap thermal energy and heat up
the atmosphere.
This is a normal occurrence and we could not survive without it.
An increase of the greenhouse gas, carbon dioxide
may be causing an increase in the greenhouse
effect. This rise in average global temperatures is
called GLOBAL WARMING.
The RADIATION BALANCE explains the
balance between incoming energy and
outgoing energy.
If greenhouse gases continue to increase the
radiation may be affected. If this balance is not
maintained, the ability of Earth to support life
may also be affected.
One way to compensate for the increase of
carbon dioxide is to plant trees. Plants absorb
the harmful carbon dioxide in their food making
process.
Atmospheric Pressure and Winds
WIND is moving air and is created by the difference in air pressure.
• The greater the pressure difference, the faster the wind blows.
• The difference in air pressure is generally caused by the unequal
heating of the Earth.
• Warm air is less dense and rises.
(Low pressure)
• Cold air is more dense and sinks.
(High pressure)
• Air generally move from areas
of high pressure to areas of low
pressure.
• Winds generally move from the
poles towards the equator.
Pressure Belts – areas of pressure created by
the movement of air. These are caused by the
uneven heating of the Earth. These belts occur
at about every 30 degrees of latitude.
The Coriolis Effect – the curving of moving objects
such as wind by the Earth’s rotation.
• The winds in the Northern
Hemisphere curve to the right.
• The winds in the Southern
Hemisphere curve to the left.
There are two main types of winds: local winds
and global winds. They are both caused by the
uneven heating of the Earth’s surface.
• Local winds generally move short distances and can blow from any direction.
• Global winds are part of air circulation that moves across the Earth. They travel longer
distances and only in a specific direction.
Global Winds
1. The DOLDRUMS are an area of low pressure around the equator. This is
where the trade winds of the Northern and Southern Hemispheres meet.
• Very little wind because of the warm, rising air.
• An Old English word meaning “foolish” because sailors were considered foolish
to get stuck there.
2. The HORSE LATITUDES are at about 30° north and 30° south latitude.
• Sinking air creates an area of high pressure with weak winds.
• Named because sailors stuck in this area would throw horses overboard to
conserve water.
3. The POLAR EASTERLIES are wind belts that extend from the poles
to 60° latitude in both hemispheres.
• Formed from cold, sinking air from the poles.
4. The JET STREAMS are narrow belts of high-speed winds that blow
in the upper troposphere and the lower stratosphere.
• Do not follow regular paths around the Earth.
• The jet streams controls the movement of storms.
5. TRADE WINDS are winds that blow from 30° north and south
latitude to the equator. The Coriolis Effect causes these winds to
curve.
• Used by early traders to sail from Europe to the Americas.
6. The WESTERLIES are wind belts found in both the Northern and
Southern Hemispheres between 30° and 60° latitude.
• Used by early traders to return to Europe.
Local Winds
Local winds are influenced by the
geography of an area.
1. SEA BREEZES are created when warm air over the
land rises creating an area of low pressure. Air from
over the water moves toward the land creating a sea
breeze.
2. LAND BREEZES are created when air over land cools
and creates an area of high pressure. The cool air
moves toward the water producing a land breeze.
(Water holds its temperature MUCH
better than land does.)
3.
VALLEY BREEZES are created when the
sun heats the valley floor and warms the
air above it. The warm air moves
upslope creating a valley breeze.
4. MOUNTAIN BREEZES are created when
the cold air from the mountains sinks
down into the valley. This is caused by
the mountains cooling faster than the
valleys.
Air Masses and Fronts
Changes in weather are caused by the movement
and interaction of air masses. AIR MASSES are
large bodies of air that have similar temperature
and moisture throughout.
Air masses get their moisture and temperature
characteristics from the area it forms over. The
characteristics of these air masses are represented
on maps with a two-letter symbol.
• The first letter indicates the moisture characteristics.
• The second letter indicates the temperature characteristics.
Symbol Meanings:
M – maritime – forms over water – wet air mass.
C – continental – forms over land – dry air mass
P – polar – forms over polar regions – cold air mass
T – tropical – forms over the Tropics – warm air
mass
Examples:
cP =
mP =
mT =
cT =
Fronts are the boundaries between air masses. Weather at a
front is usually cloudy and stormy. There are 4 types of fronts:
1. Cold front – cold air mass meets
and displaces a warm air mass. The
cold air moves under the warm air
pushing it up.
• Move fast producing
thunderstorms, heavy rain, or snow.
• Cooler weather usually follow a cold front.
2. Warm front – warm air mass meets and overrides a cold air mass. The warm air moves
over the cold air and gradually replaces it.
• Generally bring drizzly
precipitation.
• After the front has passed,
weather conditions are warm
and clear.
3.
Occluded front – faster moving cold air overtakes a slower moving warm air mass and forces the
warm air
mass up. The cold air
mass then moves on
until it meets another
cold air mass that is
warmer than it is. The
cold air mass then forces
this air mass to rise.
•
Has cool temperatures and large amounts of precipitation.
3.
Stationary front – cold air mass meets a warm air mass and little horizontal movement occurs.
•
Similar weather as that
produced by a warm front.
Make sure you know each
of the symbols
associated with the 4
types of weather
fronts!!!!!
Severe Weather
SEVERE WEATHER is weather that can
cause property damage and even death.
There are several different types of severe
weather:
1.
•
•
•
•
Thunderstorms – small, intense weather systems that produce
strong winds, heavy rain, lightning and thunder.
Occur when warm, moist air rises rapidly in an unstable
atmosphere.
Lightning is a large electrical discharge that occurs between
two oppositely charged surfaces.
Thunder is the sound that results from a lightning strike.
Severe thunderstorms may produce high winds, hail, flash
floods, and tornadoes.
2.
Tornadoes – a small, rotating column
of air that has high wind speeds and low
central pressure and that touches the
ground.
•
•
•
Starts out as a funnel cloud that pokes
through the bottom of a cumulonimbus
cloud and hangs in the air.
It is only called a tornado when it makes
contact with the Earth’s surface.
Cause a lot of damage due to their strong
spinning winds.
3.
Hurricanes – large, rotating tropical weather systems with
wind speeds of at least 119 km/h.
•
Called typhoons in the Pacific Ocean.
•
Called cyclones in the Indian Ocean.
•
Generally form in the area between 5° and 20° north or
south of the equator over warm, tropical oceans.
•
Get their energy from the condensation of water vapor.
They are fueled by contact with the warm ocean water.
•
Eye wall – group of cumulonimbus clouds that produce
heavy rains and winds.
•
Eye – core of warm, relatively calm air.
•
Rain bands – circle the center of the hurricane.