1. Announcements Exam #2: Tomorrow, 7PM, 160 English Bldg.Exam #2: Tomorrow, 7PM, 160 English Bldg. Quiz 6: Due before 7PM tomorrowQuiz 6: Due before 7PM tomorrow No Class THIS Friday: EOHNo Class THIS Friday: EOH

2. Class 21 -- The Oceans ATMOSPHERE Composition -- review, human impact Troposphere, Stratosphere ConvectionPressure Global wind patterns

4. Why do we detour and study the atmosphere? O 2 and CO 2 for life processes Greenhouse effect- linked to oceans Ocean-atm. interactions **Heat, moisture exchange** **Winds drive ocean currents**

5. Ignoring water vapor…

6. Variable constituentsVariable constituents Gases: ozone (O 3 ), CO, CH 4, N+O gases, S+O gases Aerosols: dust, pollen, water droplets Water vapor

7. Human modification Added CO 2Added CO 2 –Enhanced greenhouse effect Ozone destruction by CFC’s -- Increased UVOzone destruction by CFC’s -- Increased UV Skin diseases Skin diseases Reduces global photosynthesis ??? Reduces global photosynthesis ???

8. The global CO 2 Cycle

9. Where is most of the C found on the earth?

10. Here it comes again- CONVECTION:

12. Ionosphere- above that ATMOSPHERIC ZONES Troposphere -- 0-12 km Stratosphere -- 12-50 km

13. 1) Troposphere -- 0-12 km Heated at its base (surface) -- Heated at its base (surface) -- Convection, turbulent motion Convection, turbulent motion Warmed at bottom --> warm air risesWarmed at bottom --> warm air rises Also: Humid air tends to riseAlso: Humid air tends to rise

14. Why does the troposphere have thermal convection?

15. troposphere stratosphere warm

16. 2) Stratosphere -- 12-50 km –Stratified -- little vertical mixing –"Lid" on the turbulent troposphere –Ozone absorbs UV radiation ATMOSPHERIC ZONES

19. Weight of overlying atmos. creates pressureWeight of overlying atmos. creates pressure We don’t notice -- equal in all directionsWe don’t notice -- equal in all directions Variations in pressure: Decreases with altitudeDecreases with altitude Pressure at Earth’s surface -- varies….Pressure at Earth’s surface -- varies…. –high pressure = descending air –low pressure = ascending air ATMOSPHERIC PRESSURE

24. GLOBAL WIND SYSTEM Prevailing wind “belts” Trade Winds: Low latitudes, E --> W Westerlies: Mid latitudes, W --> E Polar Easterlies: High latitudes, E --> W What causes this pattern? 1) Convection- Temp. diff. -- Low vs. High Lat. 2) Coriolis effect (next time)

25. Global Convection in the atmosphere Equatorial zone: Hot, Humid --> rising air masses Polar zones (and elsewhere- more later) --> sinking air masses. Result: – Global convection cells – Global Wind Patterns at surface Note: Local convection cells exist, too

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

29. Coriolis Video Thanks to UIUC Atmospheric Science

30. Google: coriolis video UIUC

32. Student animations CD-ROM Coriolis effect animations

33. Coriolis Effect: Practical result: Things moving long distances on earth tend to be deflected by Coriolis “force” Deflection in N hemis.: RIGHT-HAND TURN Deflection in S hemis.: LEFT-HAND TURN

34. 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

38. 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

39. Think of a missile moving southward: Fire from North Pole, southward Watch from space- a straight line path Earth rotates beneath it But, a person in Chicago looking up at it is moving eastward in space- ~1000km/h! Ask this person: Is the missile moving due south?

40. Winds and ocean currents have both.......initial velocity and direction, and.......initial rotational velocity that depends on latitude As they cross latitudes, winds and currents are rotating at different velocities than Earth's surface Result: Apparent deflection to Earth-bound observers. always right in N.H. always left in S.H.

42. Analogy -- launching a missle from different latitudes Fire from North Pole (no rotation) Earth rotates beneath it Deflection -- to the west (right) Fire from Equator (max. rotation) Missle rotates faster than Earth beneath it Deflection -- to the east (right)

43. Amount of wind/current deflection depends on...... time of travel (how long it moves)... distance of travel (how far it moves) Winds and currents are deflected a lot because they are in continuous motion over long distances.