16.2 CHANGING WEATHER

Learning Targets

1. Describe the characteristics of air masses and how they get those characteristics

2. Discuss what happens when air masses meet

3. List the differences between stationary, cold, warm, and occluded fronts

Formation of Air Masses

1. Air with similar temperature and humidity (characteristics)

2. Source Region - Temperature and humidity based on where they form or travel across

3. May be 1000 miles across

Formation of Air Masses

1. Storms form when air mass and region it moves over have different characteristics

a) Cold air mass moving over warmer ground

i. Bottom layer heated, air rises, form clouds and precipitation

b) Warm air mass moving over colder ground

i. Forms inversions

Types of Air Masses

1. Cold air masses flow toward equator2. Warm air masses flow toward poles3. Continental (c) or Maritime (m) –

Source Regiona) Arctic (A)b) Polar (P)c) Tropical (T)d) Equatorial (E)

} Latitude

Fronts

1. Storms2. Where 2 air masses meet

a)Different temperature, humidity, density

3. Do NOT mix4. One goes up; one goes down5. Hot is less dense goes up

Stationary Front

1. Neither air mass is moving2. Steady wind and precipitation

Cold Front

1. Cold air moving into area covered by warm air

2. Cold (dense) air pushes warm (less dense) air up

a) Humidity high enough forms clouds and precipitation

b) Remember - warm air holds more moisture

Cold Front varies with Seasons

1. Spring & Summer – Air unstable create thunderstorms & tornadoes

2. Spring – If temperature gradient high, strong winds blow

3. Autumn – Strong rains4. Winter – Source region in arctic

bringing frigid temperatures and snows

Warm Front

1.Warm air moving over land covered by cold air

2.Warm air is slides over cold aira)Atmosphere is stable

create inversions

Occluded Front

1. Forms around a low pressure zone L

2. Cold front catches up with a warm front

a) Air masses are cold, warm, coldb) Variable and unpredictable

weather as the various air masses mix

c) Cyclones more on this later