Coherent intraseasonal oceanic variations in the eastern equatorial Indian Ocean and in the Lombok and Ombai Straits from observations and a high-resolution OGCM

Iskandar, Iskhaq and Masumoto, Yukio and Mizuno, K and Sasaki, H and Affandi, Azhar Kholil and Setiabudidaya, Dedi and Syamsuddin, Fadli (2014) Coherent intraseasonal oceanic variations in the eastern equatorial Indian Ocean and in the Lombok and Ombai Straits from observations and a high-resolution OGCM. J. Geophys, Res119. ISSN doi:10.1029/2013JC009592

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    Abstract

    Ongoing acoustic Doppler current profilers (ADCP) observation in the eastern equatorial Indian Ocean and a recentInternational Nusantara Stratification and Transport (INSTANT) experiment in the Indonesian Throughflow (ITF) straits have shown coherent intraseasonal oceanic variations in this region. The intraseasonal variations are dominated by 30–70 day variations, with a tendency for the observed currents in the eastern equatorial Indian Ocean to lead those at the Lombok and Ombai Straits. Phase speed of these eastward propagating signals estimated using lag correlation analysis does not correspond to one particular baroclinic mode, though it is in the range expected for the first two baroclinic modes. In this study, the dynamics underlying this intraseasonal coherency is evaluated using output from a high-resolution ocean general circulation model developed for the Earth Simulator (OFES). The results from model simulation of January 2001 through December 2007 show that the first two baroclinic modes dominate the intraseasonal variations in this region. While the first and second baroclinic modes have comparable contribution to the intraseasonal oceanic variations in the eastern equatorial Indian Ocean and in the Ombai Strait, the intraseasonal oceanic variations in the Lombok Strait are dominated by the first baroclinic mode. Moreover, the analysis reveals that the intraseasonal variability at all mooring sites is mostly confined in the upper layer above 100 m depth. Both equatorial wind from the Indian Ocean and alongshore winds off Sumatra and Java play important roles in generating intraseasonal variations in the Lombok and Ombai Straits.

    Item Type: Article
    Uncontrolled Keywords: Remote and local forcing generate intrasesoanal variation in the ITF region
    Subjects: Q Science > QC Physics
    Divisions: Faculty of Mathematics and Natural Sciences > Department of Physics
    Depositing User: Dr. Iskhaq Iskandar
    Date Deposited: 02 Feb 2015 08:48
    Last Modified: 02 Feb 2015 08:48
    URI: http://eprints.unsri.ac.id/id/eprint/5108

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