1. AIR MASSES AND FRONTS
By: Ms. Nail

2. Air Masses
An air mass is a large body of air that develops over a particular region.
Warm air forms over tropical regions near the equator. Has low air pressure.
T- Tropical
Cold air forms over polar regions. Has high air pressure
P- Polar
Wet air masses form over oceans.
m- maritime
Dry air masses from over land.
c- continental

3. Air masses Moisture content is noted by the first letter.
m – maritime – wet
c – continental – dry
Temperature is noted by the second letter.
P – polar – cool
T – tropical - warm

6. Air Masses mP- maritime polar cP – continental polar
mT – maritime tropical
cT – continental tropical

7. Fronts A front is a boundary between air masses. Cold front Warm front
Four types of fronts and map symbols
Cold front
Warm front
Occluded front
Stationary front

8. COLD FRONT
What is a cold front? A cold front forms when a cold air mass pushes under a warm air mass.
Bring thunderstorms, rain or snow.
This produces cumulonimbus clouds.
Cold front followed by cooler drier air.

9. Cold Front

10. WARM FRONT
What is a warm front? A warm front forms when a warm air mass moves up and over a cold air mass.
This produces stratus and cirrus clouds.
Brings drizzly precipitation.
Followed by clear warm weather.

11. Warm Front

12. STATIONARY FRONT
What is a stationary front? A stationary front forms when a warm air mass and a cold air mass meets but neither advances.
Many days of cloudy, wet weather.

13. Stationary Front

14. OCCLUDED FRONT
What is an occluded front? An occluded front forms when a fast moving cold air mass overtakes a slower warm air mass. The warm air is caught between two cooler air masses. The cool dense air moves under the warm less dense air and cuts the warm air mass off.
Brings cool temperatures with large amounts of rain or snow

15. Occluded Front

17. Quiz: Take this on the paper provided.
1. Describe a maritime polar (mP) air mass, in terms of moisture and temperature.
2. What is the name of an air mass that forms over water?
3. What is the name of an air mass that forms over land?
4. What is the name of an air mass that forms in a cold region?
5. What is the name of an air mass that forms in a warm region?
6. Describe a continental tropical (cT) air mass, Moisture and temperature.
7. The boundary between two air masses is called a ______________________.
8. A cold air mass meets and pushes a warm air mass out of the way.
What type of front am I?
9. A warm air mass is trapped between to cold air masses.
10. A warm air mass meets and pushes a cold air mass out of the way.
11. I am a front that brings drizzly rain and am followed by warm clear weather. Name me
12. A cold air mass meets a warm air but neither is very strong. They are separated and many days of wet , cloudy weather occur.

18. Pressure Systems What is air pressure?
The force that a column of air applies ON the air
or a surface below it. Air flows from areas of:
HIGH pressure to areas of low pressure.
Air pressure is the same thing as saying
Barometric Pressure.

19. What is a HIGH pressure system?
Circulating air with HIGH pressure at it’s center and lower
Pressure outside of the system.
In the center of a HIGH pressure system, what
happens to the density of the air?
It increases & thickens. The density of the air sinks and
move to areas of low pressure.
What does the level of density cause the air to do?
Move away from the center
What kind of weather does a high-pressure system bring?
Clear skies and fair weather. High pressure = Happy weather.

20. What kind of air mass has a HIGH pressure?
Cool Air Masses
How do the air molecules circulate in a high-pressure system?
CLOCKWISE.
AND what does it cause the air to do in terms of the center of the system?
Move DOWN & AWAY from the center of the system.
What is the weather map symbol for a high-pressure system?
(USE YOUR colors)

21. What is a LOW pressure system?
Circulating air with LOW pressure at it’s center and higher
Pressure outside of the system.
In the center of a LOW pressure system, what
happens to the density of the air?
It decreases & gets lighter; Rises and moves to areas
of high pressure.
What does the level of density cause the air to do?
Move toward the center
What kind of weather does a low-pressure system bring?
Clouds, rain or snow. Low pressure = Lousy weather.

22. What kind of air mass has a LOW pressure?
Warm Air Masses
How do the air molecules circulate in a LOW-pressure system?
COUNTER CLOCK-WISE
AND what does it cause the air to do in terms of the center of the system?
Move UP & TOWARD the center of the system.
What is the weather map symbol for a low-pressure system?
(USE YOUR COLORS)

23. What weather instrument is used to measure air pressure in the atmosphere?
Barometer, Air pressure is the SAME thing as saying Barometric pressure.
What unit of measure is used when measuring air pressure?
MILLIBARS (mb) or INCHES OF MERCURY (in.HG)

24. Compare/Contrast Chart
High and Low Pressure
High Pressure
Low Pressure
Moving inward on isobars…
Pressure Increases
Pressure Decreases
Density of air
Higher
Lower
Representation on a map
H (typically blue)
L (typically red)
Motion of air
Clockwise, air sinks
Counterclockwise, air rises
Also known as…
Anticyclone
Cyclone
Motion of air causes a zone of…
Divergence
Convergence
Stability of atmosphere
Stable
Unstable

25. High Pressure

26. LOW PRESSURE