Relation between Indian Monsoon Variability and SST

Abstract

The relation between the intraseasonal modes of the South Asian monsoon and the sea surface temperature (SST) in the tropical oceans on a daily time scale has been investigated. Long lead?lag relations of the daily SST anomalies with the dominant monsoon modes obtained from a multichannel singular spectrum analysis (MSSA) of the daily outgoing longwave radiation (OLR) over the South Asian monsoon region are presented. The dominant MSSA monsoon modes, consisting of two oscillatory modes (at 45- and 28-day time scales) and two seasonally persistent modes, are found to have varying degrees of lead?lag relation with the SSTs in the Indian and Pacific Oceans. While the 45-day oscillatory mode has weak correlations with the SSTs in the Pacific and Indian Ocean, it also reveals a possible 45-day oscillation in the SST in the northwestern Pacific and northern Indian Ocean. The 28-day oscillatory mode has negligible correlation with the tropical SST. One of the persistent monsoon modes has a very strong relation with the El Niño?Southern Oscillation (ENSO)?related SST in the Pacific with correlation above 0.8 for a long lead?lag time range. The other persistent monsoon mode has moderate lead?lag correlation with the Indian Ocean dipole (IOD) SST as well as with the ENSO-like SST in the Pacific. The strong relation of the persistent modes, which mainly determine the seasonal mean monsoon, when the SST leads, provides hope for long-term prediction of the seasonal mean monsoon. The strong relation between the monsoon and the SST, when the monsoon leads, points toward the strong influence of the monsoon on the variability of ENSO and IOD.