The socio-economic progress of a country like India strongly depends on agricultural sector and related industries and thereby to the timely and sufficient summer monsoon rainfall. So understanding of the variabilities of the summer monsoon is very important. The interannual variability of summer monsoon corresponds to biennial scale (TBO) and multi-year scale variability (ENSO). The relationship of interannual variability of monsoon to ENSO is established earlier, though the reverse relationship is weakening in recent decades. Different mechanisms involving coupled ocean-atmosphere processes...