Tele connections between Indian summer monsoon rainfall on regional scale and sea surface temperature over equatorial Pacific Ocean

Abstract

El-Nino – anomalous warming over equatorial Pacific – has been identified as one of the major teleconnections of All-India Summer Monsoon Rainfall (AISMR). The AISMR is characterized by a considerable spatial variability. The largest variance in AISMR is observed over the regions of India that receive the least rainfall. As such, it is necessary to study the variability of Indian Summer Monsoon Rainfall (ISMR) on a regional scale. Appreciating this fact, an attempt is made in this study to examine the relationship between the ISMR over the five homogeneous regions of India [identified by Parthasarathy, et al., (1995)] and the Sea Surface Temperature (SST) over central and eastern equatorial Pacific Ocean. Also, an attempt has been made to investigate on weakening of the ENSO-Monsoon relationship, on regional scale, owing to global warming, after mid-1970s, in view of some recent studies in this field. It is observed that, the SST anomalies over the Nino regions of the Pacific show an oscillatory type of lagged correlations with the summer monsoon rainfall over the five homogeneous regions of India. This relationship is very strong and statistically significant during the pre-Global Warming period (1951-75) and rather ill-defined during the post-Global Warming period (1976-2000).