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

Abstract:

Regional-scale precipitation responses over Indonesia to major climate modes in the tropical Indo–Pacific Oceans, i.e., canonical El Niño, El Niño Modoki, and the Indian Ocean Dipole (IOD), and how the responses are related to large-scale moisture flux convergences are investigated. The precipitation responses, analyzed using a high-spatial-resolution APHRODITE precipitation dataset for the period 1960–2007, exhibit differences between the dry (July–September) and wet (November–April) seasons. Canonical El Niño strongly reduces precipitation in central to eastern Indonesia in the dry season and northern Indonesia in the wet season (see Fig.), consistent with anomalous moisture flux convergence. It is found that the corresponding moisture flux convergence anomalies occur around the edge of the SPCZ (ITCZ), i.e., zero climatological convergence, in the period when seasonal migration of those edges comes to 10°–15°S (10°–15°N) from April–November (December–May) in the tropical west Pacific (see Fig.). This means that the seasonal migration of convergence zones is modulated by canonical El Niño strongly in the convergence zone edges, and this modulation explains regional and seasonal developments of precipitation responses. Similar precipitation responses are also found for El Niño Modoki associated with anomalous moisture flux convergence with slightly different spatio-temporal patterns from those for canonical El Niño. IOD reduces precipitation in southwestern Indonesia in the dry season, associated with anomalous moisture flux convergence. 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.