Tropical Indian Ocean Wind Circulation- A Shift?

It has been observed that the teleconnections between Indian Summer Monsoon Rainfall(ISMR) and the Pacific Ocean has been weakening. In conformation with the earlier findings, Warm Water Volume (WWV) of the equatorial pacific has a lead predictive skill for ISMR over the whole period. However, we find that the interannual correlations between the ENSO and ISMR have continued to weaken since 1950s, irrespective of the choice of an index for tropical pacific variability- be it the NINO4 index or even the Tropical Pacific Warm Water Volume index.

A preliminary analysis has been carried out by exploring the low level summer monsoon wind circulation. Our analysis suggests that, in the post-1977 period, the western boundary of the Walker circulation, which is important for the ISMR variability, is confined to the east of 120E. This may be due to a basinwide broadening of the cross-equatorial flow in the equatorial Indian Ocean in the recent decades. This may imply that with the decrease of influence of Pacific Ocean over the ISMR, Indian ocean seems to play an even bigger role now than it did earlier. The probable cause for this shift of winds over Indian Ocean is being studied now.