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Part 6 Air Sea Interaction

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  1. Chapter 6 Air–Sea Interaction Essentials of Oceanography 7th Edition

  2. Uneven solar heating on Earth • Solar energy in high latitudes: • Has a larger “footprint” • Is reflected to a greater extent • Passes through more atmosphere • Is less than that received in low latitudes Figure 6-1

  3. Earth’s seasons • Earth’s axis is tilted 23½º from vertical • Northern and Southern Hemispheres are alternately tilted toward and away from the Sun • Causes longer days and more intense solar radiation during summer Figure 6-2

  4. Oceanic heat flow • A net heat gain is experienced in low latitudes • A net heat loss is experienced in high latitudes • Heat gain and loss are balanced by oceanic and atmospheric circulation Figure 6-3

  5. Physical properties of the atmosphere: Composition (dry air)

  6. Physical properties of the atmosphere: Temperature • Troposphere is: • Lowermost part of the atmosphere • Where most weather occurs • Temperature of troposphere cools with increasing altitude Figure 6-4

  7. Physical properties of the atmosphere: Density • Warm, low density air rises • Cool, high density air sinks • Creates circular- moving loop of air (convection cell) Figure 6-5

  8. Physical properties of the atmosphere: Water vapor • Cool air cannot hold much water vapor, so is typically dry • Warm air can hold more water vapor, so is typically moist • Water vapor decreases the density of air

  9. Physical properties of the atmosphere: Pressure • A column of cool, dense air causes high pressure at the surface, which will lead to sinking air • A column of warm, less dense air causes low pressure at the surface, which will lead to rising air Figure 6-6

  10. Physical properties of the atmosphere: Movement • Air always moves from high-pressure regions toward low-pressure regions • Moving air is called wind

  11. The Coriolis effect • The Coriolis effect • Is a result of Earth’s rotation • Causes moving objects to follow curved paths: • In Northern Hemisphere, curvature is to right • In Southern Hemisphere, curvature is to left • Changes with latitude: • No Coriolis effect at Equator • Maximum Coriolis effect at poles

  12. A merry-go-round as an example of the Coriolis effect • To an observer above the merry-go-round, objects travel straight • To an observer on the merry-go-round, objects follow curved paths • Internet video of balls being rolled across a moving merry-go-round Figure 6-8

  13. The Coriolis effect on Earth • As Earth rotates, different latitudes travel at different speeds • The change in speed with latitude causes the Coriolis effect Figure 6-9a

  14. Missile paths demonstrate the Coriolis effect • Two missiles are fired toward a target in the Northern Hemisphere • Both missiles curve to the right Figure 6-9b

  15. Wind belts of the world Figure 6-10

  16. Characteristics of wind belts and boundaries

  17. Coriolis effect influences air movement • Northern Hemisphere winds curve to the right as they move from high to low pressure • Causes wind to circulate: • Clockwise around high-pressure regions • Counterclockwise around low-pressure regions Figure 6-12

  18. Air masses that affect U.S. weather Figure 6-14

  19. Origin and paths of tropical cyclones • Tropical cyclones are intense low pressure storms created by: • Warm water • Moist air • Coriolis effect • Includes: • Hurricanes • Cyclones • Typhoons Figure 6-16

  20. Hurricane occurrence • Hurricanes have wind speeds of at least 120 kilometers (74 miles) per hour • Worldwide, about 100 storms grow to hurricane status each year • In the Northern Hemisphere, hurricane season is generally between June 1 and November 30 • Current state of the tropical oceans

  21. Hurricane structure • Hurricanes have: • Circular cloud bands that produce torrential rain • The ability to move into the mid-latitudes • A central eye Figure 6-17 Figure 6-19a

  22. Hurricanes produce storm surge • Storm surge: • Is a rise in sea level created by hurricane coming ashore • Can be up to 12 meters (40 feet) high • Causes most destruction and fatalities associated with hurricanes Figure 6-18

  23. Climate regions of the ocean Figure 6-20

  24. How a greenhouse works • Sunlight passes through the clear covering of a greenhouse • It converts to longer wavelength heat energy • Heat cannot pass through the covering and is trapped inside Figure 6-21

  25. The heating of Earth’s atmosphere Figure 6-23

  26. Anthropogenic gases that contribute to the greenhouse effect

  27. Carbon dioxide is increasing in the atmosphere • As a result of human activities, carbon dioxide in the atmosphere has increased by 30% since 200 years ago Figure 6-24

  28. Earth’s average temperature is rising • Earth’s average surface temperature has risen at least 0.6°C (1.1°F) in the last 130 years • May be related to increase in atmospheric carbon dioxide Figure 6-25

  29. Predicted changes with increased greenhouse warming • Higher than normal sea surface temperatures that could affect world climate • More severe droughts or increased precipitation • Water contamination and outbreaks of water-borne diseases • Longer and more intense heat waves • Shifts in the distribution of plants and animals • Potential melting or enlargement of polar ice caps

  30. End of Chapter 6 Essentials of Oceanography 7th Edition