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All Journal Jurnal Silvikultur Tropika (JST) Jurnal Ilmu dan Teknologi Kelautan Tropis Indonesian Journal of Geography JOURNAL OF COASTAL DEVELOPMENT Jurnal Penelitian Fisika dan Aplikasinya (JPFA) Jurnal Matematika & Sains Journal of Mathematical and Fundamental Sciences International Journal of Advances in Intelligent Informatics JURNAL ILMIAH PENDIDIKAN FISIKA AL BIRUNI Jurnal Fisika FLUX Science and Technology Indonesia Jurnal Penelitian Sains Jurnal Penelitian Pendidikan IPA (JPPIPA) IJEMS (Indonesian Journal of Environmental Management and Sustainability) Marine Research in Indonesia Jurnal Kelautan Nasional Jurnal Ilmu Fisika International Journal of Remote Sensing and Earth Sciences (IJReSES) Jurnal Teori dan Aplikasi Fisika Indobiosains SRIWIJAYA JOURNAL OF ENVIRONMENT JIFP (Jurnal Ilmu Fisika dan Pembelajarannya) Makara Journal of Science Kemas Journal:Jurnal Pengabdian masyarakat
Iskhaq Iskandar
University Of Sriwijaya
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Journal : Journal of Mathematical and Fundamental Sciences

 1 
Observed Intraseasonal Oceanic Variations in the Eastern Equatorial Indian Ocean and in the Outflow Straits of the Indonesian Throughflow Iskhaq Iskandar; Yukio Masumoto; Keisuke Mizuno
Journal of Mathematical and Fundamental Sciences Vol. 42 No. 2 (2010)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.sci.2010.42.2.3

Abstract

The observed currents in the eastern equatorial Indian Ocean and in the outflow straits of the Indonesian Throughflow (ITF) are shown to have significant intraseasonal variations and coherency during January 2004 "“ November 2006. The wavelet analysis between the eastern equatorial Indian Ocean and the ITF straits demonstrates significant intraseasonal coherency for the observed current at 50m depth. At 150m depth, the intraseasonal coherency only occurs between the observed currents in the eastern equatorial Indian Ocean and in the Lombok and Ombai Straits. On the other hand, at 350m depth the intraseasonal coherency is only found between the eastern equatorial Indian Ocean and the Ombai Strait. This intraseasonal coherency is associated with the wind-forced equatorial Kelvin waves which propagate eastward along the equatorial and coastal wave guides. Near-surface intraseasonal variations are associated with the first baroclinic mode with typical phase speed of 2.91 ± 0.46 m s-1, while the deeper layer intraseasonal variations are associated with the second baroclinic mode with typical phase speed of 1.59 ± 0.18 m s-1. Moreover, the lag correlations between the zonal winds and the observed currents at the ITF straits further demonstrate the source of intraseasonal variations in the ITF.
The Role of Equatorial Oceanic Waves in the Activation of the 2006 Indian Ocean Dipole Iskhaq Iskandar
Journal of Mathematical and Fundamental Sciences Vol. 44 No. 2 (2012)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.sci.2012.44.2.2

Abstract

Observations and a linear wave model were used to evaluate the role of equatorial oceanic wave processes in affecting the evolution of the 2006 positive Indian Ocean Dipole (IOD), focusing on the activation phase of the event. The observations indicate the presence of upwelling equatorial waves and westward near-surface zonal currents along the equator during the activation phase of the event in August 2006. These upwelling equatorial waves (negative sea surface height anomalies) and westward zonal current anomalies contributed to significant sea surface cooling in the eastern equatorial Indian Ocean. The model results reveal that the upwelling equatorial waves and westward nearsurface zonal currents were mainly generated by wind-forced Kelvin waves associated with the easterly wind anomalies. On the other hand, anomalous easterly winds along the equator during June caused downwelling waves (positive sea surface height anomalies) in the off-equatorial region which propagated westward and elevated sea levels in the western region. The model further shows that a complex interplay of wind-forced and boundary-generated Rossby waves elevated sea levels in the western equatorial Indian Ocean during the activations phase of the 2006 IOD event.
Simulated Interannual Modulation of Intraseasonal Kelvin Waves in the Equatorial Indian Ocean Iskhaq Iskandar; Dedi Setiabudidaya; Wijaya Mardiansyah; Muhammad Irfan
Journal of Mathematical and Fundamental Sciences Vol. 48 No. 3 (2016)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2016.48.3.3

Abstract

Outputs from a high-resolution ocean general circulation model (OGCM) for the period of 1990-2003 indicate an interannual modulation of intraseasonal Kelvin waves along the equatorial Indian Ocean. During normal conditions without IOD event, the first mode explains about 30-40% of the total variance in the western (60-65ºE) and central (75-80ºE) basin, while the second mode contributes up to 45% to the total variance in the central basin around the longitude of 82ºE. In contrast, during the 1997/98 IOD event, the fourth mode caused about 40% of the total variance in the central and eastern basin. During the 1994 IOD event, the contribution from the fourth baroclinic mode in the eastern basin caused 45% of the total variance. In the central basin, the second and the fourth baroclinic mode caused almost the same variance (~40%). The variations in the characteristics of the intraseasonal Kelvin waves are related to variations in the vertical stratification. During the IOD event, the pycnocline in the eastern basin was raised by about 50 m and the stratification at the upper level is strengthened, while it is weakened at lower levels. These changes lead to an increase in the contribution of higher-order baroclinic modes.
Respective Influences of Indian Ocean Dipole and El Niño-Southern Oscillation on Indonesian Precipitation Deni Okta Lestari; Edy Sutriyono; Sabaruddin Sabaruddin; Iskhaq Iskandar
Journal of Mathematical and Fundamental Sciences Vol. 50 No. 3 (2018)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2018.50.3.3

Abstract

The respective influences of the Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation (ENSO) on Indonesian precipitation were evaluated using monthly precipitation data from the Global Precipitation Climatology Centre (GPCC) for January 1948 to December 2013. Simultaneous correlation between seasonal precipitation anomalies and climate indices for these two types of climate modes revealed that IOD events have a significant correlation with the precipitation over southern Sumatra, Java, southern Kalimantan, the Nusa Tenggara Islands, some parts of Sulawesi and eastern Papua. Meanwhile, ENSO events have a significant correlation with the precipitation over southern Sumatra, Java, Kalimantan, Sulawesi, and Papua. Droughts during the dry season (JJA and SON) typically occur when a positive IOD event simultaneously occurs with an El Niño event associated with anomalous low SST observed in the Indonesian seas and the southeastern equatorial Indian Ocean. Low SST anomalies lead to low-level wind divergence and reduce water vapor in the lower atmosphere, supress atmospheric convection over the Indonesian region and then cause a decrease in precipitation.
Co-Authors AA Sudharmawan, AA Aan Johan Wahyudi Adam Darmawan Afdal Agus Dwi Saputra Akmal Johan Aldri Frinaldi ANDY MULYANA Anindya Wirasatriya Anna IS Purwiyanto Apriani, Yosi Arsali Arsali Assaidah, Assaidah Azhar Affandi Azhar Kholiq Affandi Bahiyah, Amirotul Dedi Setiabudidaya Deni Okta Lestari Dominikus Krisna Herlambang Dwi Setyawan Eddy, Syaiful Edy Sutriyono Edy Sutriyono FAUZIYAH Fitri Agustriani Hadi Hamdi Akhsan Hilda Zulkifli Hilda Zulkifli Indra Yustian Jamiatul Khairunnisa Putri Keisuke Mizuno Khairul Saleh Khakim, Mokhamad Yusup Nur Khofaria, Hafizhu Kusuma, Willy Anta Lestrai, Deni Okta Melly Ariska Moh. Rasyid Ridho Mokhamad Yusup Nur Khakim Muhammad Abu Bakar Sidik Muhammad Hendri Muhammad Irfan Muhammad Irfan Muhammad Nur Nuril Azhar Nurjuliasti Ningsih, Ellis Pradanto Poerwono Puad Maulana Mandailing Putriyani, Fena Siska Qurnia Wulan Sari Raden Putra Rendy M. Wahid Rezi Apri Rozirwan . Sabaruddin Kadir Sabaruddin Sabaruddin SABARUDDIN, . Septi Hermialingga Sofian, Ian Mochamad Suhadi Suhadi Suhadi Suhadi Suhanda, Alfin Supari Supari Supari Supari, Supari Wijaya Mardiansyah Wijaya Mardiansyah Wijaya Mardiansyah Wijaya Mardiansyah Wijaya Mardiansyah Wijaya Mardiansyah, Wijaya Yukio Masumoto Zulfikhar Zulfikhar Zulfikhar, Zulfikhar Zulkifli Dahlan