Consequently they are approximately orthogonal.
Every event has a somewhat different and distinct character.
Nor does it determine the character of individual events in terms of different SST patterns throughout the rest of the tropical Pacific. This is the case not only throughout the tropics but, through teleconnections, in the extratropics as well. Hence, an index of average SST in one region can not adequately characterize the nature of the event. Simply characterizing the different flavors, as seen in the different structure of individual events and their evolution, has been done mainly through the indices in different parts of the tropical Pacific. In this note we describe two indices which characterize much of ENSO and its evolution.