1. El Nino? • As a team draw the El Nino cycle from last lesson below:

2. What is El Nino? • A disruption along the equatorial Pacific of the east-west Walker circulatory cell. • A phenomena caused by a warm current of water that appears every 3-7 years in the eastern Pacific ocean. • This causes unusual weather patterns in some parts of the world.

5. Trade winds blow from the east to the west (taking warm water with them) as part of the Walker circulation. Normal Conditions Low pressure and warm waters. Evaporation leads to rainfall. The cold (20oC)Humboldt current creates nutrient-rich water ideal for fishing in Peru. La Nina is a heightening of these normal condition e.g. very cold waters off west coast of South America.

6. Trade winds weaken or reverse. El Nino conditions High pressure and very dry stable conditions. Cooler water means less evaporation. Pressure lowers and warm water sloshes east. Poor fishing yields. Evaporation leads to heavy rainfall.

11. El Nino is not totally predictable but on average occurs once every four years. It usually lasts for about 18 months after it begins NOAA's satellite view of El Niño, 1997-8 El Nino U.S. hurricane damage is affected by the phase of ENSO, with increased losses during La Niñaevents and reduced losses during El Niño events.

12. storms from Atlantic more hurricanes drought flooding Possible La Nina effects La Nina La Nina is characterised by unusually cold ocean temperatures in the Equatorial Pacific, compared to El Nino, which is characterised by unusually warm ocean temperatures in the Equatorial Pacific. In general, La Nina events tend to cause less widespread weather extremes than El Nino.

13. (b) Explain how El Niño cycles can lead to drought(5) • Expect explanations, which may include some description, of how El Nino leads to drought: • El Nino cycles occur roughly 3 – 7 years in the Pacific Ocean  • Colder water off Australia/ Indonesia / Asia  • Explains colder water means less evaporation so drought on land – Australia/ Indonesia / Asia  • Role of high pressure / anti –cyclone conditions plays in drought for western regions  • Explains change /cycle is associated with trade winds weakening / reversing  • And may develop this (e.g provides accurate account of warm weather ‘sloshing’ east, or details of cold currents)  • Credit La Nina droughts (as part of cycles) e.g. intensification of dry conditions in South America  • Credit definition of drought  and explanations of human factors that exacerbate drought in Australia. • Credit accurately drawn diagram(s) used to support the answer. Also credit other valid and located drought ideas and concepts (teleconnections ideas ideas, Walker circulation). • Do not credit details of what is happening in low pressure / high rainfall / flood rich regions or impacts of drought.

14. Useful Link – El Nino FAQs! • http://www.elnino.noaa.gov/lanina_new_faq.html