Download air mass - Ms. D. Science CGPA

Weather Patterns
Table of Contents
6.3
Masses and Their Movements
Vocabulary 6.3
1. Air mass: A huge body of air that has similar temperature, humidity, and
air pressure at any given time.
2. Maritime A humid air mass that forms over oceans.
3. Continental A dry air mass that forms over land.
4. Tropical: A warm air mass that forms in the tropics and has low pressure.
5. Polar: a cold air mass that forms 50 degrees north latitude or south
latitude of 50 degrees south latitude and has high air pressure.
6. Jet Stream- bands of high-speed winds about 10 km above Earth’s
surface.
7. Front- The boundary where unlike air masses meet but do not mix.
8. Occluded- Cut off, as in a front where warm air mass is caught between
two cooler air masses.
9. Cyclone- A swirling center of low-pressure air.
10. Anticyclone- A high-pressure center of dry air.
(Prefix anti= opposite of)
What are the Major Air Masses?
An air mass is a huge body of air in the lower atmosphere that has
similar temperature, humidity, and air pressure at any given height.
Four major types of air masses influence the weather in North
America:
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•
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maritime tropical
continental tropical
maritime polar
continental polar.
temperature
Characteristics of an air mass:
humidity
Major Air Masses
Maritime
Continental
air masses form over the ocean and can be very humid.
air masses form over land, and are drier than maritime air masses.
Tropical
air masses are warm, form in the tropics, and have low air
pressure.
Polar
air masses are cold, form near the poles, and have high air
pressure.
In North America, most air masses move from WEST to EAST
Air Masses and Their Movements
Types of Air Masses
Air masses can be classified according to temperature and humidity.
Air Masses and Their Movements
North American Air Masses
Air masses can be warm or cold, and humid or dry.
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What Are the Major Air Masses? Pg. 203
How Air Masses Move type of air mass (cold/warm)
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•
When air masses interacts with other air masses, it causes the weather to
change.
In the U.S., air masses are moved by prevailing westerlies and jet streams.
The ___________ ____________, the major wind belts over the continental U.S.
push air masses from west to east.
The jet stream is a band of _______-_______ wind about 10 kilometers above the
surface of Earth that pushes air masses along. (within Prevailing winds)
Fronts (The boundary where air masses meet but do not mix) occur along the boundaries
between air masses.
Changeable weather develops along fronts.
What Are the Main Types of Fronts? Pg.204
Air masses collide and can form four types of
fronts:
cold front , warm front, stationary front ,occluded
fronts
When a faster cold air mass runs into a slower
warm air mass, a cold front forms. The cold air
slides under the warm air. As the warm air rises,
it cools and condenses, often resulting in heavy
rain or snow.
When a faster warm air mass runs into a slower
cold air mass, a warm front forms. The warm
air slides up over the cold air, possibly causing
light rain or snow.
direction the move
The characteristic of front depends on:
temperature
What Are the Main Types of Fronts? Pg.205
• When a cold air mass and warm air
mass collide, but neither displaces the
other, a stationary front occurs. Water
vapor in the warm air condenses into
rain, snow, fog, or clouds, lingering
for days.
• When a warm air mass is caught
between two cooler air masses, the
warm air is pushed up and an
occluded front forms. (The warm air
mass is cut off, or occluded, from the
ground.) Temperatures at the ground
get cooler, and it may get cloudy and
rain or snow.
Air Masses and Their Movements
Types of Fronts
What type of weather is brought by each front?
What Weather Do Cyclones and Anticyclones Bring? Pg. 206
swirling center of low-pressure air is
called a cyclone. In the Northern
Hemisphere, cyclones spin
counterclockwise when viewed from
above. Cyclones and decreasing air
pressure are associated with
clouds, wind, and precipitation.
An anticyclone is the opposite of a
cyclone. The descending air in an
anticyclone generally causes dry
clear weather
Air Masses and Their Movements
Cyclones and Anticyclones
Which image is a cyclone and which is an anticyclone? What is the air
motion direction of each?
Air Masses and Their Movements
Which circles are low-pressure centers and which are high-pressure
centers?
Clouds
Cirrus
Cloud Types
There are many
different types of
clouds.
Cirrocumulus
Cumulonimbus
Altocumulus
Altostratus
Cumulus
Nimbostratus
Stratus
Fog