Download Air and Weather p. D12-17

Air and Weather
p. D12-17
Ingredients of Weather
•Air
•Wind
•Moisture
Greenhouse Effect
• Heat from the sun that is trapped in
Earth’s atmosphere
• This is how the planet is warmed
Air Masses
• Huge bodies of air that can cover
thousands of miles
• Two properties-moisture and
temperature
• Moist air masses - form over water
• Dry masses - form over land
• Warm masses- form near the equator
• Cold masses- form near the poles
Polar Air Masses
•Bring cold, dry air
Tropical Air Masses
•Bring warm, moist air
Weather Fronts
• When air masses meet, they
don’t mix.
• Instead, they form a border
called a “front”.
• Active weather happens along
these fronts.
Cold Front
• Forms when cold air catches up with
warm air.
• The cold air pushes the warm air
higher up in the atmosphere.
• Rising warm air cools and forms
clouds.
• Rain develops.
• Storms often develop along a cold
front.
Warm Front
• Forms when warm air catches up to
cold air.
• The warm air slides up over the cold
air.
• Clouds form.
• Precipitation may fall as the front
passes.
• Then the sky clears and the
temperatures rise.
Stationary Front
• This is a front that stops moving.
• It may stay in one place for
several days.
• If precipitation is involved, heavy
rain or snow may fall.
Clouds
• Clouds form along fronts.
• Therefore, they can help
meteorologists predict
weather.
Cirrus Clouds
• High-altitude clouds
• Made of ice crystals
• Winds stretch them into long, wispy
horsetail or feather shapes.
• Mean cool, fair weather.
Cumulonimbus Clouds
“Storm Clouds”
• Associated with a cold front
• Towering and dark or gray-white
• Usually mean rain or storms
Cumulus Clouds
• Puffy cotton-ball clouds
• Seen on clear, warm days
• May eventually become cumulonimbus, or
storm clouds
Stratus Clouds
• Seen on gray, cloudy days
• Form in low, dark layers
• May bring rain or snow