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Impacts of the Indonesian Throughflow on Rainfalls over Indonesia

Author(s): Han Soo Lee; Tsuyosi Ikeda; Takao Yamashita

Linked Author(s): Han Soo Lee

Keywords: Rainfall; Indonesian Throughflow; Indonesia; El Nino; La Nina; Indian Ocean Dipole

Abstract: Analyses on the relationships between the observed rainfall records and the ENSO and SST variations of the Pacific and Indian Oceans were conducted on a 1°latitude-longitude grid over Indonesia for a 26-year period from January 1985 to August 2010 using the Global Summary of the Day rainfall records from 173 stations throughout the Indonesian islands. The indices used for the ENSO and SST variations were the Multivariate ENSO Index (MEI), the Pacific Decadal Oscillation (PDO), NINO1+2, NINO3, NINO3.4, NINO4, the Dipole Mode Index (DMI) for the Indian Ocean Dipole (IOD), and the Indian Ocean basin-wide (IOBW). From the results, in Western Indonesia as defined in this paper, the Southern Sumatra and Southern Java Islands facing the Indian Ocean were positively correlated with a negative IOD period, as demonstrated by other studies, whereas the northwestern Sumatra Island was positively correlated with a positive IOD period. In Eastern Indonesia, the rainfalls were positively correlated with La Ni? a episodes. The PDO index was also strongly correlated with the rainfall in this region. In Central Indonesia, seasonal variations due to monsoons are predominant, and there were strong negative and positive correlations with the MEI and NINO. WEST, respectively, indicating high rainfalls during strong La Ni? a episodes. The orographic effect of mountain regions in the Sumatra and Java Islands was also noticeable in the rainfall characteristics. The interesting high negative and positive correlations with MEI and NINO. WEST, respectively, in Central Indonesia led us to further analyse the impacts of the Indonesian Throughflow (ITF) on the rainfalls over the region. From the 4 case scenarios based on the Pacific-Indian head difference due to the relative SSTs of each ocean, the ITF could impact the rainfalls along its pathway regions, as indicated by the correlation results. However, further studies are needed with more qualified long-term data to validate the relationship between the ITF and rainfalls.


Year: 2012

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