El Niño–Indian summer monsoon relation—a nonlinear scale interactive energy exchange perspective

Abstract El Nino, the major large-scale driver of the Indian summer monsoon (ISM), being a trans-oceanic phenomenon, is nonlinearly related to ISM. The mechanistic exploration of this nonlinearity and its quantification in the energy exchange perspective has been demonstrated in this chapter. Considering El Nino as a low frequency oscillation having a time period of 12–18 months, the mechanism of El Nino—monsoon nonlinear relation is explored by quantifying this nonlinearity in terms of interscale transfer of kinetic energy through the process of nonlinear triad interactions in the frequency domain. The study illustrates that the variability of ISM rainfall is strongly dictated by the contrasting nonlinear interactions of El Nino with high and low frequency dominant monsoon modes and are examined for two opposite relationships between El Nino and ISM. This work has paved a way to propel further research in the space of nonlinearities through scale interaction mechanisms between these two large-scale phenomenon.