Trend and variability in the long‐term relationship between Eurasian snow cover and Indian summer monsoon rainfall

Abstract

AbstractThe predictability of the Indian summer monsoon rainfall (ISMR) at any given time period depends on the strength of its relationship with predictable drivers like the El Nino–Southern Oscillation (ENSO) that are known to undergo significant epochal variations. While a similar relationship between the Eurasian snow cover fraction (SCF) and ISMR has also shown epochal variation in recent decades, its stationarity on centennial or longer timescales remains unknown. Here, on the basis of the observed relationship between the dominant modes of ISMR and SCF over a period of 115 years (1901–2015), we unravel two indices of SCF that encapsulate its space–time variability. We find that the SCF indices and ISMR relationship have a statistically significant increasing trend with a weak multidecadal variability superimposed on it, making significant positive correlations between the two highly probable in the coming decades. With SCF driving the North Atlantic Oscillation (NAO) that in turn driving the ISMR, we find that the NAO plays a pivotal role in modulating the SCF–ISMR teleconnection on a multidecadal time scale. Further, the SCF also regulates the ISMR low‐frequency variability through modulation of the tropospheric temperature gradient of the Indian region.