1. Atmospheric Circulation and Weather Systems

2. Take-Away Points
Weather is driven by unequal solar heating and cooling
Air motions are affected by the Coriolis Effect and “centrifugal” force
High and Low Pressure Systems
Air flows parallel to pressure contours (Geostrophic winds)
Air masses meet along sharp boundaries or fronts
Weather is inherently chaotic and that limits our ability to forecast it

3. The Seasons

4. 1. Weather is driven by unequal solar heating and cooling
Heat Lag
1. Weather is driven by unequal solar heating and cooling

5. Heat Lag

6. Atmospheric Circulation
1. Weather is driven by unequal solar heating and cooling

7. Atmospheric Circulation
1. Weather is driven by unequal solar heating and cooling

8. 1. Weather is driven by unequal solar heating and cooling
Asymmetric Earth
1. Weather is driven by unequal solar heating and cooling

9. 1. Weather is driven by unequal solar heating and cooling
Asymmetric Earth
1. Weather is driven by unequal solar heating and cooling

10. Atmospheric Circulation
1. Weather is driven by unequal solar heating and cooling

11. Zonal and Meridional Flow
1. Weather is driven by unequal solar heating and cooling

12. Semi-Permanent Features, January
1. Weather is driven by unequal solar heating and cooling

13. Semi-Permanent Features, July
1. Weather is driven by unequal solar heating and cooling

14. Rotation Effects
2. Air motions are affected by the Coriolis Effect and “centrifugal” force

15. The Coriolis Effect Due to moving on a rotating earth
Things on equator are moving faster than points near poles
Affects:
Winds
Ocean Currents
Tides
2. Air motions are affected by the Coriolis Effect and “centrifugal” force

16. The Coriolis Effect
Things moving toward the equator are deflected west
Things moving poleward are deflected east
Deflected to Right in Northern Hemisphere
Deflected to Left in Southern Hemisphere
2. Air motions are affected by the Coriolis Effect and “centrifugal” force

17. The Coriolis Effect
2. Air motions are affected by the Coriolis Effect and “centrifugal” force

18. The Coriolis Effect
2. Air motions are affected by the Coriolis Effect and “centrifugal” force

19. The Coriolis Effect
2. Air motions are affected by the Coriolis Effect and “centrifugal” force

20. Inertial Circles
2. Air motions are affected by the Coriolis Effect and “centrifugal” force

21. “Centrifugal” Force ?
2. Air motions are affected by the Coriolis Effect and “centrifugal” force

22. Or No Force?
2. Air motions are affected by the Coriolis Effect and “centrifugal” force

23. “Centrifugal” Force Does Not Exist
When anything turns, the only forces that act are in the direction of the turn
These forces are called centripetal (center-seeking) force
“Centrifugal” force is an illusion
“Centrifugal” force is due to inertia and centripetal force opposing each other
2. Air motions are affected by the Coriolis Effect and “centrifugal” force

24. 3. High and Low Pressure Systems
High Pressure Systems
3. High and Low Pressure Systems

25. 3. High and Low Pressure Systems
High Pressure Systems
Air flows out from center
Spin clockwise in Northern Hemisphere
No air mixing
Stable, fair weather
Sinking Air, few clouds
Long duration can result in inversions, pollution
Winter: often extreme cold
Cold Air is Dense
Clear Skies and Radiational Cooling
3. High and Low Pressure Systems

26. 3. High and Low Pressure Systems

27. 3. High and Low Pressure Systems
Why Counterclockwise?
3. High and Low Pressure Systems

28. 3. High and Low Pressure Systems
Air flows in toward center
Spin counter-clockwise in Northern Hemisphere
Mixes air of different properties
Associated with fronts
Stormy, sometimes violent weather
Passage often results in sharp change in weather conditions
3. High and Low Pressure Systems

29. 4. Air flows parallel to pressure contours (Geostrophic winds)
As air flows in or out of pressure cells, Coriolis Effect deflects it
At surface, friction limits the deflection.
Winds blow about 45 degree angles to isobars
Aloft, friction not a factor
Deflection continues until limited by pressure gradient (winds can’t go against pressure)
Winds blow parallel to contours
This is called geostrophic flow
4. Air flows parallel to pressure contours (Geostrophic winds)

30. Geostrophic Flow

31. Geostrophic Flow

32. 4. Air flows parallel to pressure contours (Geostrophic winds)
Geostrophic Flow
4. Air flows parallel to pressure contours (Geostrophic winds)

33. 1905 Weather Map of US

34. First U.S. Weather Map With Fronts

35. Fronts and Low Pressure Systems
5. Air masses meet along sharp boundaries or fronts

36. 5. Air masses meet along sharp boundaries or fronts

37. 5. Air masses meet along sharp boundaries or fronts
Warm Fronts
5. Air masses meet along sharp boundaries or fronts

38. 5. Air masses meet along sharp boundaries or fronts
Warm Fronts
Gradual Onset
Warm Air over Cool Air
Little Turbulence
Weather Rarely Violent
5. Air masses meet along sharp boundaries or fronts

39. 5. Air masses meet along sharp boundaries or fronts
Cold Fronts
5. Air masses meet along sharp boundaries or fronts

40. 5. Air masses meet along sharp boundaries or fronts
Cold Fronts
Abrupt Onset
Cold Air Lifting Warm Air
Considerable Turbulence
Weather Sometimes Violent
Thunderstorms Common
Can Spawn Tornadoes
5. Air masses meet along sharp boundaries or fronts

41. Old Low Pressure Systems
5. Air masses meet along sharp boundaries or fronts

42. 5. Air masses meet along sharp boundaries or fronts
Occluded Fronts
5. Air masses meet along sharp boundaries or fronts

43. 5. Air masses meet along sharp boundaries or fronts
Occluded Fronts
Two fronts merge
Any two types of front can occlude
Most common: Cold Front overtakes Warm Front
Starts off like a warm front, finishes like a cold front
5. Air masses meet along sharp boundaries or fronts

44. 5. Air masses meet along sharp boundaries or fronts
Weather Prediction
5. Air masses meet along sharp boundaries or fronts

45. 5. Air masses meet along sharp boundaries or fronts
Weather Prediction
5. Air masses meet along sharp boundaries or fronts

46. 5. Air masses meet along sharp boundaries or fronts
Weather Prediction
5. Air masses meet along sharp boundaries or fronts

47. Chaos x

48. Does Not Mean: Chaos Theory Cloned Dinosaurs will run amok
Systems do not follow physical laws
Systems behave with wild unpredictability
Systems do not have limits
Phenomena cannot be predicted
6. Weather is inherently chaotic and that limits our ability to forecast it

49. Does Mean: Chaos Theory Small differences compound over time
There are limits to how accurately phenomena can be predicted
Examples:
Weather
The Planets
Traffic
6. Weather is inherently chaotic and that limits our ability to forecast it