International audienceThis paper uses recent gridded and historical data in order to assess the relationships betweeninterannual variability of the Indian Summer Monsoon (ISM) and Sea Surface Temperature (SST)anomaly patterns over the Indian and Pacific oceans.Interannual variability of ISM rainfall and dynamical indices for the traditional summer monsoonseason (June-September) are strongly influenced by rainfall and circulation anomalies observedduring August and September, or the Late Indian Summer Monsoon (LISM). Anomalous monsoonsare linked to well-defined LISM rainfall and large-scale circulation anomalies. The east-westWalker and local Hadley circulations fluctuate during the LISM of anomalous ISM years. LISMcirculation is weakened and shifted eastward during weak ISM years. Therefore, we focus on thepredictability of the LISM in this study.Strong (weak) (L)ISMs are preceded by significant positive (negative) SST anomalies in thesoutheastern subtropical Indian Ocean, off Australia, during boreal winter. These SST anomaliesare mainly linked to south Indian Ocean dipole events, recently studied by Behera and Yamagata(2001), and to the El Niño-Southern Oscillation (ENSO) phenomenon. These SST anomalies arehighly persistent and affect the northwestward translation of the Mascarene high from austral toboreal summer. The southeastward (northwestward) shift of this subtropical high associated withcold (warm) SST anomalies off Australia causes a weakening (strengthening) of the wholemonsoon circulation through a modulation of the local Hadley cell during the LISM. Furthermore, itis suggested that the Mascarene high interacts with the underlying SST anomalies through apositive dynamical feedback mechanism, maintaining its anomalous position during the LISM.Our results also explain why a strong ISM is preceded by a transition in boreal spring from an ElNiño to a La Niña state in the Pacific and vice versa. An El Niño event and the associated warmSST anomalies over the southeastern Indian Ocean during boreal winter may play a key role in thedevelopment of a strong ISM by strengthening the local Hadley circulation during the LISM. On theother hand, a developing La Niña event in boreal spring and summer may also enhance the eastwestWalker circulation and the monsoon as demonstrated in many previous studies
