From AMS Glossary
A direct cell oriented along the equator; originally used by Bjerknes (1969) to refer to the cell induced by the contrast between the warm waters of the western Pacific and the cooler waters of the eastern Pacific.
Variability in this cell is associated with the Southern Oscillation. The term is now sometimes used to refer to the entire chain of east–west equatorial circulation cells that stretches around the globe.
Bjerknes, J. 1969. Tellus. 18. 820–829.