2. Atmospheric Motion

3. Nonrotating Earth Equator – Warming and rising of air – Rising air cools as it ascends – Surface winds blow towards equator to replace ascending air Poles – Cool, dry air descends

5. Global Wind Bands Hadley cells – Subtropical cells – Air rises at the equator due to solar heating, and falls due to cooling at ~30º

6. Global Wind Bands Ferrel cells – Temperate cells – Occurs between 30º and 50-60º latitude – Some air descending at 30º turns poleward

7. Global Wind Bands Polar cells – Centered over each pole – At 50-60º, the air is warm and wet enough to ascend, but too dense to mix with Ferrel cell

8. Wind Patterns Between Cells: – Vertical air movement – Weak surface winds Within Cells: – Horizontal air movement – Strong surface winds

9. Wind Patterns Between Cells: Hadley cells – Doldrums Near the equator Decrease in pressure gradient Variable breezes – Intertropical Convergence Zone (ITCZ)

10. Wind Patterns Between Cells: Hadley and Ferrel cells – Horse latitudes 30º latitude Subtropical high pressure Sinking air; dry – Many deserts are found at this latitude

11. Wind Patterns Within Cells: – Hadley cell Trade Winds – Easterlies Centered at 15º – Ferrel cell Westerlies Centered at 45º – Polar cell Easterlies 60-90º

13. Radiation and Latitude More heat gained at equator More heat lost at higher latitudes

15. Atmospheric Pressure

17. High vs. Low Pressure High Pressure Cell Anticyclonic rotation (clockwise) in N hemisphere Downward vertical motion Air is compressed and warmed Dry weather

18. High vs. Low Pressure Low Pressure Cell Cyclonic rotation (counter clockwise in N hemisphere) Upward vertical motion Air expands and cools as it rises Wet weather

19. Fig. 8.16

21. Wind Band Modification Seasonal Changes

22. Wind Band Modification Seasonal Changes

23. Wind Band Modification Seasonal Changes

24. Wind Band Modification Seasonal Changes

25. Monsoons - Summer Land heats more rapidly than ocean Air above land expands and rises creating low pressure Cool air flows from ocean Cool air is heated, expands, rises and condenses

26. Monsoons - Winter Land cools more rapidly than ocean Air contracts and sinks creating high pressure Dry surface winds move seaward

27. Onshore & Offshore Breezes (small, daily mini-monsoons) Onshore Breeze

28. Onshore & Offshore Breezes (small, daily mini-monsoons) Offshore Breeze

29. Topographic Effect Windward = wet Leeward = dry

30. Rain shadow

31. Jet Streams High speed winds in the upper troposphere Polar Subtropical Weather of temperate zone

33. Hurricanes Easterly wave > 26.5  C (80  F) Typhoon or cyclone

35. Hurricanes

36. El Niño – Southern Oscillation

38. El Niño Sea surface topography and temperature Normal El Niño End of El Niño

39. La Niña Colder phases

40. Storm Surge Low atmospheric pressure Strong onshore winds