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Monsoon and extratropical climate

Monsoon and extratropical climate. Review of last lecture. Mean state: The two basic regions of SST? Which region has stronger rainfall? What is the Walker circulation? El Nino and La Nina: Which region has warm SST anomaly during El Nino? 4-year period. Global impacts of ENSO

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Monsoon and extratropical climate

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  1. Monsoon and extratropical climate

  2. Review of last lecture • Mean state: The two basic regions of SST? Which region has stronger rainfall? What is the Walker circulation? • El Nino and La Nina: Which region has warm SST anomaly during El Nino? 4-year period. • Global impacts of ENSO • Effects of El Nino on U.S. winter temperature and precipitation: Warm temperature around Great Lakes, Heavy rainfall in California and Gulf coast

  3. Land-sea Contrast: Seasonal “Monsoon” Seasonal temperature distributions: • T decreases poleward • Isotherms shift seasonally • T over land > water in summer

  4. Temperature Ranges (Summer minus Winter) Large over land, small over ocean

  5. The Seasonal “Monsoon” • A seasonal reversal of wind due to seasonal thermal differences between landmasses and large water bodies • is characterized by dry, offshore flow conditions during cool months and wet, onshore flow conditions during warm months. • Orographic lifting often enhances precipitation totals

  6. A 3D view of the Indian summer monsoon

  7. Seasonal variation of monsoon rainfall

  8. World’s major monsoon systems From Jay Fein 1987

  9. Impacts of monsoons:(1) Normal year Dry season Wet season

  10. Impacts of monsoons:(2) Failure of monsoon and droughts Drought affected area in Karnataka, India, 2012, image from Wikipedia

  11. Impacts of monsoons:(3) Excessive monsoon and floods Image from Doctors without Borders

  12. Video: Pakistan flood in 2010 http://www.youtube.com/watch?v=beCVQqqTlKQ

  13. Extratropical Climate

  14. Mean State • Westerly winds and jet streams • A constant Polar Vortex: transport/mixing, important for ozone hole

  15. The Pacific/North American Oscillation (PNA): The way El Nino/La Nina affect U.S.

  16. The Strengthening/Weakening of Polar Vortex • North Pole: Arctic Oscillation (AO) North Atlantic Oscillation (NAO) • South Pole: Antarctic Oscillation (AAO)

  17. The Arctic Oscillation • Positive phase: Stronger polar vortex, colder temperature over Greenland, warm winter in U.S. • Negative phase: Weaker polar vortex, warmer temperature over Greenland, cold winter in U.S.

  18. The Arctic Oscillation (AO) index • The AO does not have a preferred oscillation period, making it difficult to predict

  19. Tropical-extratropical Interaction • Zonal mean (3 cells) • ENSO • The interactions are mutual

  20. Summary Tropical climate: • Land-sea contrasts: seasonal monsoon Extratropical climate: • Mean state: westerly winds, polar vortex • What is the primary way El Nino affect extratropics? (PNA) • The oscillations associated with strengthening/weakening of polar vortex: AO, NAO, AAO

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