1. Impacts of El Nino Observations Mechanisms for remote impacts

2. Observations

3. Growth and Decay of El Nino

7. A closer look at impacts http://iri.columbia.edu/climate/ENSO ENSO and CLIMATE Temperature and Precipitation Tropical Cyclones ENSO and SOCIETY Regional impacts http://www.pmel.noaa.gov/tao/elnino/impacts.html

8. Mechanisms for remote impacts Latent heating associated with tropical precipitation anomalies excites waves in the atmosphere: –Atmospheric equatorial Kelvin and Rossby waves propagate zonally. Associated subsidence warms troposphere and suppresses precipitation –Rossby waves can also propagate into extratropics (especially in winter) causing large- scale circulation anomalies which impact weather. (Note that propagation requires a westerly mean flow and the relevant Rossby waves have an eastward group velocity)

9. Source: D. Neelin

11. Impacts on the North Atlantic Region El Nino – La Nina La Nina El Nino

12. Yearly average of Chlorophyll concentrations 1997 1998 El Niño low La Niña high Impacts on marine ecosystems Source: A. Timmermann

13. El Nino Prediction

14. El Nino research issues Phase locking to seasonal cycle (onset and termination) What determines and limits the amplitude of El Nino? What controls the frequency of El Nino events? How will El Nino respond to anthropogenic climate change?