1. Air-Sea Interactions
The atmosphere and ocean form a coupled system, exchanging heat, momentum and water at the interface.
Emmanuel, K. A. 1986: An air-sea interaction theory for tropical cyclones. Part 1: steady state maintenance. J. Atm. Sci

2. OBJECTIVES To understand air-sea interaction through teleconnections:
Planetary Waves
ENSO indices
NAO and the NAO index
To understand the global effects of large scale air sea interactions

3. Normal

4. El Niño

5. La Niña

6. Rossby Waves
Rossby waves, also known as planetary waves owe their origin to the shape and rotation of the earth
Travel from east to west, following latitude
Slow moving
Speed varies with latitude slower near the pole, faster near the Equator
On the order of a few cm/s (or a few km/day)

8. Influence of Rossby Waves

9. Kelvin Waves
Special gravity waves excited by an abrupt change in the overlying wind field
Travel west to east
Fast moving
Speeds of approximately 2-3 m/s (250 km/day) at the surface
Maximum amplitude at the Equator

10. Equatorial Kelvin Waves

11. Influence of Kelvin Waves
Warmest water is usually
m below the surface

12. Rossby and Kelvin Waves

13. Rossby and Kelvin Waves

14. Defining ENSO Events Multivariate ENSO Index (MEI)
Based on six observed variables over the tropical Pacific: sea-level pressure, components of the surface wind, SST, surface air temperature, and total cloudiness fraction
Southern Oscillation Index (SOI)
Measures monthly, or seasonal, fluctuation in pressure between Tahiti and Darwin
Niño 3.4/Oceanic Niño Index (ONI)
3 month running mean of SST anomalies in the 3.4 region

15. MEI
Blue: cold events (La Nina)
Red: warm events (El Nino)

16. SOI

17. TAO/TRITON Array
Tropical Atmospheric Ocean Project - real-time data from moored ocean buoys for improved detection, understanding and prediction of El Niño and La Niña.
The array consists of approximately 70 moorings in the Tropical Pacific Ocean, sending oceanographic and meteorological data to shore in real-time via the Argos satellite system.
The array is a major component of ENSO Observing System, the Global Climate Observing System (GCOS) and the Global Ocean Observing System (GOOS).
Support is provided primarily by the US and Japan

18. SOI
SST

19. Niño 3.4/ONI

20. SST Departures (˚C) Longitude Time
Since January 2011, negative SST anomalies have weakened in the central and eastern Pacific.
Recent equatorial SST anomalies are near zero across much of the Pacific.

21. SST Departures (˚C)
During the last four weeks, equatorial SSTs were near-average across the Pacific.
During the last 30 days, SST anomalies decreased in the extreme eastern tropical Pacific.

22. Niño 3.4/ONI

23. North Atlantic Oscillation
The NAO is the dominant mode of winter climate variability in the North Atlantic region ranging from central North America to Europe and much into Northern Asia.
The NAO is a large scale see-saw in atmospheric mass between the subtropical high and the polar low.
The corresponding index varies from year to year, but also exhibits a tendency to remain in one phase for intervals lasting several years.

24. Positive Phase of NAO Stronger subtropical high and Icelandic low
Increased pressure gradient results in more and stronger winter storms across the Atlantic on a more northerly track
Warm and wet winters in Europe; colder and drier in northern Canada and Greenland
US east coast experiences mild, wet winter conditions

25. Negative Phase of NAO
A weaker than normal subtropical high and Icelandic low
Reduced pressure gradient results in fewer, and weaker, winter storms on a more east-west track across the Atlantic
Moist air into the Mediterranean; cold air into northern Europe
US east coast has more cold air outbreaks and snowy conditions
Greenland has milder winter temperatures

26. NAO

27. NAO Index

28. Why Study Teleconnections?
There are correlations between these oscillations and our local climates
Impact every day life
Flooding, ‘Snowmageddon’ (DC 2010), Drought, Fires
Major impacts on the economy
Agriculture, Construction, Energy, Retail
US economic impact of the strong ’97/’98 El Niño -- $25 Billion!!
The mild mid-west winter resulted in:
Retail sales up 15%
Snow equipment sales down 35%
Skiing down - up in the west

31. Effects of El Niño/ La Niña

32. Effects of El Niño