Indian Ocean‐monsoon coupled interactions and impending monsoon droughts

Monsoon droughts over the Indian subcontinent emanate from failures in the seasonal (June–September) monsoon rains. While prolonged dry‐spells (“monsoon‐breaks”) pervade on sub‐seasonal/intra‐seasonal time‐scales, the underlying causes for these long‐lasting anomalies remain elusive. Based on analyses of a suite of observed data sets, we report an ocean‐atmosphere dynamical coupling on intra‐seasonal time‐scales, in the tropical Indian Ocean, which is pivotal in forcing extended monsoon‐breaks and causing droughts over the subcontinent. This coupling involves a feedback between the monsoonal flow and thermocline depth in the Equatorial Eastern Indian Ocean (EEIO), in which an anomaly of the summer monsoon circulation induces downwelling and maintains a higher‐than‐normal heat‐content. The near‐equatorial anomalies induce strong and sustained suppression of monsoon rainfall over the subcontinent. It is concluded that the intra‐seasonal evolution of the ocean‐monsoon coupled system is a vital key to unlocking the dynamics of monsoon droughts.