Air Masses, Global Winds, and Fronts

1. Air Masses, Global Winds, and Fronts

2. Meteorology, Weather and Climate • Meteorology is the study of atmospheric phenomena. Meteorology includes weather and climate. • Weather is the short-term variations in atmospheric phenomena that interact and interfere with the environment and life. • Climate is the long-term variations of weather in a certain area.

4. Doppler Effect • Used in radar devices to detect precipitation speed and direction • http://science.howstuffworks.com/27963-assignment-discovery-doppler-effect-video.htm

5. Air Masses An air massis a large volume of air that has the same characteristics, such as humidity and temperature, as its source region. A source region is the area over which an air mass forms.

6. Source Regions • Tropical • Polar • Arctic • Continental • Maritime

8. Global Wind Systems The directions of Earth’s winds are influenced by Earth’s rotation. This Coriolis effect results in fluids and objects moving in an apparent curved path rather than a straight line. http://www.youtube.com/watch?v=iCvaWWr_7GU&playnext=1&list=PL63987D0DF2D5AEDD&feature=results_main

9. Global Wind Systems The directions of Earth’s wind systems, such as the polar easterlies and the trade winds, vary with the latitudes in which they occur.

10. Global Wind Systems Polar easterlies The polar easterliesare the wind zones between 60 N latitude and the north pole, and 60 S latitude and the south pole. Prevailing westerlies The prevailing westerlies are the wind systems on Earth located between latitudes 30 N and 60 N, and 30 S and 60 S.

11. Global Wind Systems Trade winds Between latitudes 30 N and 30 S are two circulation belts of wind known as the trade winds. Near latitudes 30 N and 30 S, the sinking air associated with the trade winds creates an area of high pressure. This results in a belt of weak surface winds called the horse latitudes.

12. Global Wind Systems Trade winds Trade winds from the North and the South meet and join near the equator.The air is forced upward, which creates an area of low pressure. This process, called convergence, can occur on a small or large scale. Near the equator, it occurs over a large area called the intertropical convergence zone (ITCZ).

13. Global Wind Systems

14. Global Wind Systems

16. Jet Streams A jet streamis a narrow band of fast, high-altitude, westerly wind. Weather in the middle latitudes is strongly influenced by fast-moving, high-altitude jet streams.

17. Jet Streams Types of jet streams The major jet streams, called the polar jet streams, separate the polar easterlies from the prevailing westerlies. The minor jet streams are the subtropical jet streams. They occur where the trade winds meet the prevailing westerlies.

18. Fronts There are four types of fronts: • Cold Front • Warm Front • Stationary Front • Occluded Front

19. Cold Fronts Cold Fronts occur when cold, dense air displaces warm, less dense air forcing it up along a steep slope. This collision results in intense precipitation and sometimes thunderstorms.

20. Warm Fronts Warm fronts occur when advancing warm air displaces cold air developing a gradual boundary slope. Often causes widespread light precipitation.

21. Stationary Fronts Stationary Fronts occur when two air masses meet but neither advances resulting in light winds and precipitation.

22. Occluded Fronts Occluded fronts occur when a cold air mass moves so rapidly that it overtakes a warm front forcing the warm air upward. Strong winds and heavy precipitation are common along an occluded front.

23. Cold Front Warm Front Occluded Front Stationary Front

25. Pressure Systems In the northern hemisphere, winds move counterclockwise around a low-pressure center, and clockwise around a high-pressure center. Low-pressure center High-pressure center

26. Pulling it all together: • http://www.youtube.com/watch?v=LD4hSW2mys0