1. Chapter 7 Circulation of the Atmosphere The Atmosphere 9e Lutgens & Tarbuck Power Point by Michael C. LoPresto

2. Microscale

3. Atmospheric Circulation Scales
Distance
Time scale
Examples
Macroscale
Planetary
Synoptic
1000 – 40,000 km
100 – 500 km
Weeks or more
Days to weeks
Westerlies
Hurricanes
Mesoscale
1 – 100 km
Minutes to hours
Thunderstorms, Land-sea breeze
Microscale
< 1km
Seconds to minutes
Gusts, dust devils

4. Mesoscale Sea Breeze (occurs in afternoon)

5. Mesoscale Land Breeze (occurs in early morning)

6. Valley Breeze (afternoon)

7. Mountain Breeze (early morning)

8. Other Common, Named Mesoscale Winds
Chinook – warm winter wind that descends off mountains (Foehn in Alps; Santa Ana in So. Cal.)
Katabatic – cold, powerful winter wind that descends off glaciers (mistral in Alps)

9. Over-simplified global model (why is it wrong?)
Macroscale: Global Circulation
Over-simplified global model (why is it wrong?)

10. Best Model for Global Circulation

11. Idealized & Actual Prevailing Global Winds

15. Seasonal Pressure and Wind Patterns

16. January Average Global Pressure and Winds

17. July Average Global Pressure and Winds

18. Monsoons Seasonal wind (and precipitation) events on large continents
Cooling of land during winter creates high pressure, pushes air offshore (cold dry winds)
Heating of land during summer creates low pressure, sucks air inland (warm wet winds)

19. Winter Monsoon Circulation

20. Summer Monsoon Circulation

21. North American
Monsoon L

22. The Westerlies and the Jet Stream

23. Jet Stream

24. Jet Stream

25. 300 mb Equal-Pressure Surface 4.15.05

26. 300 mb Equal-Pressure Surface 4.15.05

27. Rossby Waves

28. Meridional and Zonal Flow

29. Ocean Currents

30. El Nino/Southern Oscillation

33. Effects of El Nino

34. ENSO El Nino Winter Surface Air Pressure Anomaly low high high low
La Nina Winter Surface Air Pressure Anomaly

35. 1997 ENSO Movie http://www.noaanews.noaa.gov/stories/s997.htm

36. ENSO Movie

37. Average Tropical Pacific Sea Surface Temperature

38. Sea Surface Temperature March 2002

39. ENSO Rainfall in North America
El Nino Winter Precipitation Rate Anomaly
La Nina Winter Precipitation Rate Anomaly

40. Current ENSO conditions: Equatorial Pacific sea surface temperatures (top) and temperature anomalies (bottom)

41. Worldwide ENSO Effects
Drought
Flooding, erosion
Tropical Storms
Drought
Drought
Drought
Utah: On average, ENSO years are normal, but some ENSO years have brought severe flooding
Worldwide ENSO Effects
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