Interdependence between El‐Niño/Southern Oscillation and Indian monsoon is analyzed with the use of Granger causality estimation from data for the period 1871–2006. Four different versions of the Niño‐3 and Niño‐3.4 index are used to check robustness of the results. We reveal a non‐symmetric bidirectional and even alternating character of coupling that extends previous knowledge about the presence of negative correlation and intervals of phase synchrony between the processes.

Abstract-The relationship between El Niño/Southern Oscillation (ENSO) and the Indian monsoon is analyzed using cross wavelet analysis and Granger causality estimation from empirical data for the period 1871-2003. In addition to the previously known negative correlation between the processes analyzed, their bidirectional coupling is detected and characteristics of its inertia and nonlinearity are estimated. The results from an analysis of variations in coupling characteristics in a moving window with a width ranging from 10 to 100 years demonstrate an alternation of different regimes of processes interaction, including intervals of almost unidirectional coupling.