What is normal Walker circulation?
The Walker Circulation refers to an east-west circulation of the atmosphere above the tropical Pacific, with air rising above warmer ocean regions (normally in the west), and descending over the cooler ocean areas (normally in the east).
What is Walker circulation?
THE WALKER CIRCULATION is an atmospheric system of air flow in the equatorial Pacific Ocean. The trade winds across the tropical Pacific flow from east to west: air rises above the warm waters of the western Pacific, flows eastward at high altitudes, and descends over the eastern Pacific.
What is Walker oscillation?
The east–west pressure gradient associated with the Walker circulation undergoes an irregular interannual variation. This global-scale “see-saw” in pressure, and its associated changes in patterns of wind, temperature, and precipitation, was named the southern oscillation by Walker.
What does a positive SOI mean?
Southern Oscillation Index
The Southern Oscillation Index (SOI) is a measure of the intensity or strength of the Walker Circulation. Sustained positive SOI values above about +8 indicate a La Niña event while sustained negative values below about –8 indicate an El Niño.
In what part of the world is the Walker circulation found?
Convection associated with rising branches of the Walker Circulation is found over the Maritime continent, northern South America, and eastern Africa. NOAA Climate.gov drawing by Fiona Martin. What creates such a broad, large-scale circulation along the equator?
What is Walker circulation Upsc?
The Walker circulation is the result of a difference in surface pressure and temperature over the western and eastern tropical Pacific Ocean. This air circulation displaces surface water towards the western pacific causing cold water from beneath the ocean to move upward.
What does El Niño cause?
El Niño causes the Pacific jet stream to move south and spread further east. During winter, this leads to wetter conditions than usual in the Southern U.S. and warmer and drier conditions in the North. El Niño also has a strong effect on marine life off the Pacific coast.
How long does La Niña last in Australia?
Although La Niña can sometimes persist for two years, seasonal forecasting agencies, such as the Bureau of Meteorology, are predicting neutral conditions for the rest of the year and next summer. The strong La Niña event of 2010/2011 resulted in massive floods in Queensland.
Is SOI positive during El Niño?
During La Niña (positive SOI), the pressure is higher than average (red) over the central Pacific near Tahiti, and lower than average (gray) over Australia. During El Niño, the SOI is negative, and the anomalies are reversed.
How does the Walker circulation work in El Nino?
The Walker Circulation is basically a thermally (fancy word for temperature) direct circulation that relies on temperature differences to drive the rising and sinking branches. During ENSO events like El Niño and La Niña, this circulation gets either pushed or pulled around (El Niño) or sent into overdrive (La Niña) across the Pacific.
When does the Walker circulation rise and fall?
During neutral ENSO conditions, upward branches of the Walker Circulation rise strongly across the Maritime Continent and more weakly over eastern Africa and northern South America. These rising branches coincide with bull’s-eyes of precipitation during December through February.
What is the relative strength of the Walker circulation?
The relative strength of the rising branch over South America is between those two extremes. The Walker Circulation is basically a thermally (fancy word for temperature) direct circulation that relies on temperature differences to drive the rising and sinking branches.
How is the Walker circulation related to the ocean circulation?
In addition to the air circulations describe above, there are also ocean circulations associated with the Walker circulation (see figure 21.28b above). As warm near-surface ocean water is pushed from east to west, the deeper cooler water along the eastern Pacific coast rises to the surface to fill the gap.