qBased on the delayed oscillator theory of ENSO, the ocean basin has to be big enough to produce the “delayed” from ocean wave propagation and reflection.
qIt can be shown that only the Pacific Ocean is “big” (wide) enough to produce such delayed for the ENSO cycle.
qIt is generally believed that the Atlantic Ocean may produce ENSO-like oscillation if external forcing are applied to the Atlantic Ocean.
qAlthough the Indian Ocean is considered too small to produce ENSO.