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.