Possible Roles of Atlantic Circulations on the Weakening Indian Monsoon Rainfall - ENSO Relationship

Abstract

Since the 1970s, the inverse relationship between the Indian monsoon rainfall and the El Nin˜o–Southern Oscillation (ENSO) has weakened considerably. The cause for this breakdown is shown to be most likely the strengthening and poleward shift of the jet stream over the North Atlantic. These changes have led to the recent development of a significant correlation between wintertime western European surface air temperatures and the ensuing monsoon rainfall. This western Europe winter signal extended eastward over most of northern Eurasia and remained evident in spring, such that the effect of the resulting meridional temperature contrast was able to disrupt the influence of ENSO on the monsoon.