Maritime Continent salinity as a new predictor for South Asian summer monsoon rainfall

On the basis of the synergistic seasonal evolution of sea surface salinity over the Maritime Continent (MC SSS) and South Asian rainfall, the singular value decomposition analysis is used to identify a robust coupled mode between springtime MC SSS and South Asian summer monsoon rainfall (SASMR). High MC SSS is accompanied by a SASMR dipole (suppressed rainfall in northern India and enhanced rainfall in the eastern Tibetan Plateau), which is largely caused by the negative and positive moisture flux convergence associated with ocean-to-land moisture transport. In addition, the negative rainfall anomalies in northern India decrease evapotranspiration and further suppress Indian summer monsoon rainfall (ISMR) because of land-to-atmosphere feedback. The seasonal forecast of ISMR can be improved by incorporating SSS into a physics-based empirical model, which was selected according to adjusted R² values, Mallows’ C_p values, and cross-validation. In this study, we found that a new predictor (ocean salinity) over the MC region can improve ISMR prediction, which highlights the importance of enhanced monitoring of salinity in the MC region.