Indonesian Rainfall Variability: Impacts of ENSO and Local Air–Sea Interaction

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Abstract
Relationships between Indonesian rainfall and Indo-Pacific sea surface temperatures (SSTs) and circulation anomalies are investigated using observations for 1951–97. Indonesia receives significant rainfall year-round but experiences a wet season that peaks in January and a dry season that peaks in August. Dry season rainfall anomalies are spatially coherent, strongly correlated with SST, and tightly coupled to El Niño–Southern Oscillation (ENSO) variations in the Pacific basin. Drought conditions typically occur during El Niño, when SSTs surrounding Indonesia are cool and the Walker circulation is weakened, resulting in anomalous surface easterlies across Indonesia. The opposite tends to occur during La Niña. Broadscale Indonesian rainfall and SST anomalies tend to not persist from the dry season into the wet season. Rainfall in the heart of the wet season tends to be uncorrelated with SST and spatially incoherent. Seasonally varying feedback between Indonesian SST, winds, and rainfall explains t... Abstract Relationships between Indonesian rainfall and Indo-Pacific sea surface temperatures (SSTs) and circulation anomalies are investigated using observations for 1951–97. Indonesia receives significant rainfall year-round but experiences a wet season that peaks in January and a dry season that peaks in August. Dry season rainfall anomalies are spatially coherent, strongly correlated with SST, and tightly coupled to El Niño–Southern Oscillation (ENSO) variations in the Pacific basin. Drought conditions typically occur during El Niño, when SSTs surrounding Indonesia are cool and the Walker circulation is weakened, resulting in anomalous surface easterlies across Indonesia. The opposite tends to occur during La Niña. Broadscale Indonesian rainfall and SST anomalies tend to not persist from the dry season into the wet season. Rainfall in the heart of the wet season tends to be uncorrelated with SST and spatially incoherent. Seasonally varying feedback between Indonesian SST, winds, and rainfall explains t...