1. Class 22 -- The Oceans ATMOSPHERE CIRCULATION AND WINDS Coriolis effect Prevailing winds and vertical circulation Factors modifying these winds -- Differential heating of land and sea

2. What drives the global wind patterns? Warm, moist air rising at low latitudes Cold, dry air sinking at higher latitudes

3. Fig. 6-7 If the earth were NOT rotating, convection cells in the atmosphere would look like this.

5. http://ww2010.atmos.uiuc.edu/

7. Coriolis effect Winds traveling long distances are deflected …turn to the right in Northern Hemis. …turn to the left in Southern Hemis. Why? --Speed due to earth’s rotation… 90˚ 0 km/hr 60˚ 800 km/hr 30˚1400 km/hr 0˚1600 km/hr 0˚1600 km/hr

8. But a person in Chicago is moving toward the east at ~1000 km/hr. Missile fired exactly southward from the north pole. Viewed from space, the missile follows a straight path.... What does that person see?

9. Student animations CD-ROM Coriolis effect animations

11. Coriolis Effect: Practical result: Things moving long distances on earth tends to be deflected by Coriolis “force”Things moving long distances on earth tends to be deflected by Coriolis “force” Deflection in N hemis.: “TO THE RIGHT” …(i.e., right hand turn relative to initial direction)Deflection in N hemis.: “TO THE RIGHT” …(i.e., right hand turn relative to initial direction) …in S hemis.: TO THE LEFT…in S hemis.: TO THE LEFT

12. Amount of deflection depends on...... time of travel (how long it moves)... distance of travel (how far it moves) Winds are deflected a large amount- they move for long time periods over long distances.

14. Fig. 6-7 If the earth were NOT rotating, convection cells in the atmosphere would look like this.

17. GLOBAL WIND SYSTEM Major zones Trade Winds Westerlies Polar Easterlies

19. 1. Convection Cells Occur at the Global scale, the continental scale, and the local scale Land/Ocean surface

20. Convergent & divergent zones between cells : Convergent -- air masses come together + riseConvergent -- air masses come together + rise Divergent -- sinking air comes down and spreads outDivergent -- sinking air comes down and spreads out

21. Descending air: –high atm. Pressure, dry air Ascending air:Ascending air: –low atm. Pressure, rising moist air, high rainfall

23. 1. Convection Cells Occur at the Global scale, the continental scale, and the local scale Earth surface

24. Seasonal heating/cooling cycles Daily “ / “ “ Oceans and lakes -- little T changeOceans and lakes -- little T change Land areas -- greater T changeLand areas -- greater T change Wind patterns, cont’d -- Air vs. land Temperature Contrasts:

25. Daily cycle of winds in many places: (think Miami Beach) Day: onshore winds Night: offshore winds Example 1. Convection in coastal areas

26. Day Night

27. San Francisco in the summer: Leave your shorts at home!

28. Land heats up- air risesLand heats up- air rises Onshore winds bring warm, moist air over cool water (upwelling)Onshore winds bring warm, moist air over cool water (upwelling) This creates Fog- moves inlandThis creates Fog- moves inland

29. Same idea, larger scale: Summer: Hot continent - rising air above it Creates onshore winds (and rain) Winter: Cold continent, offshore winds 2. Seasonal monsoon winds (India, Southeast Asia)

31. Summer (Wet) Winter (Dry)

32. Summer Winter

33. 3. Seasonal changes in H and L pressure zones over continents and oceans Land Ocean Summer- Where’s the Low Pressure Area?

34. Land Ocean Where’s the High Pressure Area? Winter

35. Winter: Low Pressure areas over oceans High ….. continents

36. Winter: Low Pressure areas over oceans High ….. continents JanuaryFig. 6-11

37. Summer: High Pressure areas over oceans Low …. continents January

38. 4. Winds circle around low/high pressure zones: Coriolis effect: Northern Hemisphere: Clockwise around H’sClockwise around H’s Counterclockwise around L’sCounterclockwise around L’s These motions are superimposed on the Trades, Westerlies, etc.These motions are superimposed on the Trades, Westerlies, etc. 4 Jan., 2008

43. Hot, humid air rising-- Intense LOW PRESSURE High Storm tides- sea surface “dome” in low-P center Plus wind-driven surface currents Flooding of coastal areas Hurricanes

46. Summer

47. Winter