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Chapter 17

Chapter 17. EQ. 1. What are air masses?. Air mass- large volume of air that takes on the characteristics of the land or water below it. Continental Air Mass- forms over land , air becomes dry as is loses moisture to dry land below it.

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Chapter 17

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  1. Chapter 17

  2. EQ. 1. What are air masses? Air mass- large volume of air that takes on the characteristics of the land or water below it. Continental Air Mass-forms over land , air becomes dry as is loses moisture to dry land below it.

  3. Maritime air mass-air mass forms over water, it is a moist air mass Continental or Maritime- first word in the name of an air mass Tropical or Polar-2nd word in name of air mass Tropical – forms near the equator, air becomes warm as it gains energy from warm land or water.

  4. Polar air mass- forms far from equator, air becomes cool as it loses energy to cold land or water below it. *Air masses move from where they form by global winds. As it moves it carries its characteristic moisture and temperature. If the air moves slowly, it picks up new characteristics. If it moves rapidly it carries its characteristics with it.

  5. This is why we in the south sometimes have very cold wintery blasts from Canada. The cold air masses move very quickly.

  6. EQ 2: What happens when air masses meet. P. 26 • Air masses have fronts. These fronts usually bring stormy or cloudy weather as it passes. This happens because of the differences in the two air masses that surround it. • Cold, dense air pushes warm air makes a cold front. • Warm air pushes colder air makes a warm front.

  7. Cold fronts move quickly- • Cold dense air pushes warm less dense air upward. It condenses and produces rain and sometimes thunderstorms. (cumulonimbus clouds) • Warm fronts move slowly. Warm air moves up and over a mass of cold air. Can bring many days of rain. After front passes, air is warm

  8. Stationary fronts- occur when air masses first meet or when a cold or warm front stops moving. • If the boundary between 2 air masses stays in the same location it is said to be stationary or not moving. • The air in the masses can move sideways or up but remain in the same place.

  9. High pressure system- formed when air moves all the way around a high pressure center. Most high pressure systems are large and change slowly. Low pressure system- is a large weather system that surrounds the center of low pressure. It begins as air moves around and in ward toward the lowest pressure and then up to higher altitudes.

  10. A low pressure system can develop wherever there is a center of low pressure. This usually happens along a boundary between a warm air mass and a cold air mass.

  11. EQ –How do hurricanes form? Hurricanes begin as tropical storms, a low pressure system that starts near the equator with winds blowing at 40 mph. As the wind speed increases to 74 mph, a tropical storm becomes a hurricane. Hurricanes in the western Pacific and Indian oceans are called cyclones or typhoons. Energy from warm water fuels the storm . Warm water needs to be approximately 80 degrees.

  12. 4.Trade winds move the storm westward over water and near land they can move north, south or even back eastward. 5. At the center of a hurricane there is a small area of clear calm weather 10---30 miles wide know as the eye of the hurricane. 6. The eyewall is a very fast spinning ring of cumulonimbus clouds moving upward. The ring produces heavy rain and tremendous winds. 7. Farther out, bands of rain and heavy clouds spiral inward toward the eye.

  13. Effects of hurricanes: Storm surge- when a hurricane move into coastal areas it often pushes huge masses of water onto the land. During the storm surge the sea level rises several meters backing up rivers and flooding the shore. Effects of Hurricanes Storm surge, strong winds, heavy rain, tornadoes, floods, and huge waves. Define the following: Blizzards, lake effect snow, ice storms. (page 586-587.

  14. EQ- How do thunderstorms form? • Thunderstorms get their energy from humid air. When warm, humid air near the ground moves vertically into cooler air above, the rising air or updraft can build into a thunderstorm quickly. Rising humid air forms a cumulus cloud. The water vapor releases energy when it condenses into cloud droplets. The energy increases the air motion. The cloud continues to build into a cumulonimbus cloud. • Ice crystals form in the low temperatures near the top. These crystals grow large and begin to fall and pull cold air down with them.

  15. This brings strong wind, heavy rain and/or hail. This is the most severe stage of the thunderstorm. • The downdraft can spread out and block more warm air from moving upward in the clouds. • Thunderstorms can form at a cold front or within an air mass.

  16. Effects of a thunderstorm: • Flash floods • Winds • Hail • Lightning • Tornadoes can form during thunderstorms. A tornado is a violently rotating column of air stretching from a cloud to the ground. A tornado moves along the ground in a winding path under the cloud.

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