ENSO and the temperature of the North Equatorial Counter Current

A study using the CESM climate model shows that when the sea surface temperatures are above 28.9 °C, increases in the temperature of the North Equatorial Counter Current result in significant increases in deep atmospheric convection above the Inter-Tropical Convergence Zone. This changes the longitudinal structure of the Hadley Circulation and so may have a global impact on weather and climate. At the same time, sea level atmospheric pressure increases over the Indian Ocean and decreases in the central and south-west Pacific Ocean, in a pattern similar to that of the Southern Oscillation. The longitudinal pressure gradient in the Central Pacific drops leading to weaker surface easterlies, reduced ocean upwelling along the Equator and increases in some near surface ocean temperatures. Together the results imply that the monthly and annual variations in the temperature of the North Equatorial Counter Current are responsible, at least in part, for many of the atmospheric and oceanic features associated with the El Niño and the Southern Oscillation.