El Nino and La Nina.

El Nino and La Nina are the two complementary phases of the Southern Oscillation. During El Nino, the area of high sea surface temperatures increases, while the atmospheric convection zones of the tropical Pacific expand and merge so that there is a tendency toward spatially homogeneous conditions. La Nina is associated with low sea surface temperatures near the equator, with atmospheric convergence zones that are isolated from each other, and with spatial scales smaller than those of El Nino. It is proposed that both phases of the Southern Oscillation can be attributed to unstable interactions between the tropical ocean and atmosphere. The zonal integral of winds along the equator, rather than winds over a relatively small part of the Pacific such as the region west of the date line, is identified as a useful indicator of subsequent developments in the Pacific. -from Author