1. Chapter 11: Movement in the Atmosphere

2. Movement in the Atmosphere
Air Mass – a huge body of air that has somewhat uniform temperature and humidity and covers hundreds or thousands of square kilometers of the earth’s surface
Squall Line – a line of violent thunderstorms that may occur just before a cold front arrives
(Cold fronts usually arrive faster than warm fronts, and when they force warm air to rise quickly, heavy showers and thunderstorms often follow.)
Monsoon – a season of heavy rain that lasts about 6 months in SE Asia
Cause: As the sun heats the land during the summer, hot air rises, creating low pressure area. Moist air from above the ocean flows into this partial “vacuum” and moisture falls as rain.

3. Movement in the Atmosphere
3 factors affecting wind flow and direction –
1: Horizontal atmospheric pressure differences
When a mass of air has a higher pressure on one side than the other, it will be pushed in the direction of the lower pressure
2: Coriolis Effect - Deflection due to earth’s rotation
Stronger the farther wind is from the equator and the greater the wind speed
3: Friction - Force opposing the motion of winds
Stronger closer to ground and greater the wind speed
How a sea breeze forms
Land absorbs energy from sun
Warmed air above land is less dense
Colder air over the sea is more dense, so it has a higher pressure
Cold air moves into the low pressure area over the land

4. Movement in the Atmosphere
Trade winds – consistent winds extending from the subtropical highs toward the equator, turned by the Coriolis effect into easterlies. They were formerly used by sailing ships to go from Europe to North and South America.
Polar easterlies – winds blowing consistently from NE to SW from northern polar region, bringing cold, dry air to the northern parts of North America, Asia, and Europe.
Why doldrums and horse latitudes are dangerous for sailing vessels – the air flowing straight up or down provides no wind

5. Movement in the Atmosphere
Trade winds – consistent winds extending from the subtropical highs toward the equator, turned by the Coriolis effect into easterlies. They were formerly used by sailing ships to go from Europe to North and South America.
Polar easterlies – winds blowing consistently from NE to SW from northern polar region, bringing cold, dry air to the northern parts of North America, Asia, and Europe.
Why doldrums and horse latitudes are dangerous for sailing vessels – the air flowing straight up or down provides no wind

6. Movement in the Atmosphere
What is the most common type of violent storm?
Thunderstorms
Lightning – an electrical discharge that occurs either between clouds or between a cloud and the ground
Fun Facts:
Estimated temperatures as high as 50,000 degrees F!
Calculate the distance to the storm: Count seconds between lightning and thunder. Sound travels 1/3km per second… For 15 sec. = 15 x (1/3) = 5 km

7. Movement in the Atmosphere
Tornado – a narrow funnel cloud extending down from a cumulonimbus cloud
Waterspouts – tornadoes occurring at sea (less intense than those over land)
Hurricane – giant cyclonic wind storms that form over the tropical or subtropical oceans; bring high winds and rain
Measure miles across!
Last up to 3 weeks!
Winds can be over 200 miles/hr.!
Eye – the center of a hurricane; clouds are thin and rain may stop completely; area of lowest atmospheric pressure