1. Air Masses and Fronts

2. Air Mass: Large section of the troposphere
uniform temperature
Uniform humidity
As air masses move from one area to another they bring
changes in the temperature
Changes in the

3. Two Categories of Air Masses
Maritime: Air mass that originates over the ocean and has
Dry air
Moist air
Continental: Air mass that originates of land and has

4. The Four Kinds of Air Masses
Maritime Tropical (mT)
Originates in the tropics
Warm and humid
Continental Tropical (cT)
Originates in tropical land masses
Hot and dry
Continental Polar (cP)
Originates of high altitude land areas (Canada)
Dry and cold
Maritime Polar (mP)
Originates over cold polar ocean (Gulf of Alaska)
Cold and humid

5. Weather in CA Which type of air mass controls our weather?
Continental Tropical
Continental Polar
Maritime Polar
Maritime Tropical

6. Weather in CA C. Dominated by Maritime Polar (mP)
Originates over cold polar ocean (Gulf of Alaska)
Cold and humid

7. Fronts Front: a boundary between two air masses
Warm air always rises over cool air
Fronts are associated with stormy conditions

8. Cold Front
A cold front: the transition zone where a cold air mass is replacing a warmer air mass.
Associated with
a. low pressure
b. High pressure
c. No pressure

9. Cold Front- draw this

10. Cold Front the cold air mass meets warmer air mass ahead of it
The less dense warm air rises & cools
water vapor condenses & clouds form

11. Cold Front
Which of these symbols represents a cold front on a weather map? A C B

12. Cold Front
As air moves vertically at a cold front, what type of clouds would form?
Stratus clouds
Cumulus clouds
No clouds
Cold clouds
In particular, cumulonimbus clouds, which can cause thunderstorms

13. Warm Front
A warm front: the transition zone where a warm air mass is replacing a cold air mass.
Draw this:

14. a warm air mass (in yellow) meets a colder air mass (in blue) ahead of it
The less dense warm moist air behind the front is lifted upward and "overrides" the colder air
As the air rises, it cools
widespread clouds (fog) and precipitation develop until the front passes.

15. Warm Front
As air moves horizontally at a warm front, what type of clouds would form?
Stratus clouds
Cumulus clouds
No clouds
Warm clouds

16. Warm Front
Which of these symbols represents a warm front on a weather map? A C B

17. Stationary Front When a warm or cold front stops moving, it becomes
a stationary front.
Neither air mass is
strong enough to advance
Can remain for several days
Clouds and precipitation
Once this boundary moves again, it once again becomes a warm front or cold front.

18. Occluded Front
when a cold front overtakes a warm front because it moves faster
Forms in areas of low pressure
Usually brings even colder drier weather than before, sometimes thunderstorms.

19. Temperature Inversions
A reversal of the normal temperature profile in the lower atmosphere
Cooler air gets trapped underneath warmer air
Can trap pollutants
Often occurs in valleys