Air Masses and Fronts

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

Two Categories of Air Masses

Maritime: Air mass that originates over the ocean and has

a. Dry air

b. Moist air

Continental: Air mass that originates of land and has

a. Dry air

b. Moist air

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

Weather in CA Which type of air mass controls our

weather?

A. Continental Tropical

B. Continental Polar

C. Maritime Polar

D. Maritime Tropical

Weather in CA

C. Dominated by Maritime Polar (mP) Originates over

cold polar ocean (Gulf of Alaska)

Cold and humid

Fronts Front: a boundary between two air

masses Warm air always rises over cool air Fronts are associated with stormy

conditions

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

Cold Front- draw this

Cold Front1. the cold air mass meets warmer air mass ahead of it

2. The less dense warm air rises & cools

3. water vapor condenses & clouds form

Cold Front

Which of these symbols represents a cold front on a weather map?

AB C

Cold Front As air moves vertically at

a cold front, what type of clouds would form?

A. Stratus clouds

B. Cumulus clouds

C. No clouds

D. Cold clouds

In particular, cumulonimbus clouds, which can cause thunderstorms

Warm Front A warm front: the transition zone where a warm air mass

is replacing a cold air mass.

Draw this:

1. a warm air mass (in yellow) meets a colder air mass (in blue) ahead of it

2. The less dense warm moist air behind the front is lifted upward and "overrides" the colder air

3. As the air rises, it cools4. widespread clouds (fog) and

precipitation develop until the front passes.

Warm Front As air moves horizontally at a warm front,

what type of clouds would form?

A. Stratus clouds

B. Cumulus clouds

C. No clouds

D. Warm clouds

Warm Front

Which of these symbols represents a warm front on a weather map?

AB C

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.

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.

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