Indian Ocean and Asian Monsoon Influences on Indonesian Drought: Climate Signals in Tree Rings and Corals

We investigate a tree-ring and coral-based reconstruction of the Palmer Drought Severity Index (PDSI) for Java, Indonesia that preserves a history of ENSO and Indian Ocean dipole (IOD) related extremes over recent centuries. Extreme Javan droughts correspond well to known ENSO and IOD events during this period. Although Java droughts typically show the expected association with El Nino-like conditions and failed Indian monsoons, others (mainly linked to positive IOD conditions) co-occur with a strengthened Indian monsoon, suggesting linkages between the monsoon, Indonesian drought and Indian Ocean climate variability. An index of Indian Ocean dipole sea surface temperatures (SSTs), when combined with Nino-3.4 SSTs, provides a more accurate model of Java drought than Nino-3.4 SSTs alone. This result has implications for forecasting rainfall and crop productivity in the western part of the country most influenced by Indian Ocean climate variability.