Swapping of the Pacific and Atlantic Nino influences on north central India summer monsoon

The highly populated north central India receives 90% of annual rainfall during June to September. The interannual variation of summer monsoon rainfall is less studied compared to central and western India, due to its weak signal with the El-Nino-Southern Oscillation (ENSO). Previous studies have reported a marked decadal variation in the ENSO influences on north India rainfall, but the teleconnections of this variation are not satisfactorily understood. A pathway of the changing ENSO influences on north central India rainfall is revealed from observational data analysis and numerical experiments. While La Nina-like conditions produce anomalous northeasterly wind over India and reduce the tropospheric wind shear, the emergence of the Atlantic Nino appears to overtake this ENSO influence. The Atlantic Nino intensifies the meridional stationary wave affecting pressure anomaly over northwest Europe. This excites the Eurasian Rossby wave train along the mid-latitude producing upper-troposphere high pressure anomaly, subsequently affecting north India. Future work should examine the extent to which these teleconnections are represented in climate forecast models to aid the seasonal prediction of north central India rainfall.