Relations between Interannual Variability of Regional-Scale Indonesian Precipitation and Large-Scale Climate Modes during 1960-2007

Regional-scale precipitation responses over Indonesia to major climate modes in the tropical Indo-Pacific Oceans, namely canonical El Nino, El Nino Modoki, and the Indian Ocean dipole (IOD), and how the responses are related to large-scale moisture convergences are investigated. The precipitation responses, analyzed using a high-spatial-resolution (0.5 degrees x 0.5 degrees) terrestrial precipitation dataset for the period 1960-2007, exhibit differences between the dry (July-September) and wet (November-April) seasons. Canonical El Nino strongly reduces precipitation in central to eastern Indonesia from the dry season to the early wet season and northern Indonesia in the wet season. El Nino Modoki also reduces precipitation in central to eastern Indonesia during the dry season, but conversely increases precipitation in western Indonesia in the wet season. Moisture flux analysis indicates that corresponding to the dry (wet) season precipitation reduction due to the canonical El Nino and El Nino Modoki anomalous divergence occurs around the southern (northern) edge of the convergence zone when one of the two edges is located near the equator (10 degrees S-15 degrees N) associated with their seasonal migration. This largely explains the seasonality and regionality of precipitation responses to canonical El Nino and El Nino Modoki. IOD reduces precipitation in southwestern Indonesia in the dry season, associated with anomalous moisture flux divergence. The seasonality of precipitation response to IOD is likely to be controlled by the seasonality of local sea surface temperature anomalies in the eastern pole of the IOD.