What are the Southern Oscillation and Southern Oscillation Index (SOI)?
The fluctuations in ocean temperatures during El Nio and La Nia are accompanied by even larger-scale fluctuations in air pressure between the western and eastern tropical Pacific known as the Southern Oscillation. During El Nio higher than average air pressure covers Indonesia and the western tropical Pacific and below-average air pressure covers the eastern tropical Pacific. These pressure departures are reversed during La Nia, which features below-average air pressure over Indonesia and the western tropical Pacific and above-average air pressure over the eastern tropical Pacific. Show me the surface air pressure patterns for El Nio and La Nia. The Southern Oscillation Index (SOI) is designed to measure the strength and phase of the Southern Oscillation. The SOI is calculated using departures from normal in the surface air pressure difference between Tahiti, French Polynesia and Darwin, Australia. These stations are used because of their long data records. During El Nio episodes the S
