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All Journal Jurnal Matematika & Sains Science and Technology Indonesia Jurnal Penelitian Sains Jurnal Locus Penelitian dan Pengabdian Makara Journal of Science
Wijaya Mardiansyah, Wijaya
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Aerospace Engineering Automotive Engineering Biochemistry, Genetics & Molecular Biology Chemical Engineering, Chemistry & Bioengineering Chemistry Decision Sciences, Operations Research & Management Electrical & Electronics Engineering Environmental Science Materials Science & Nanotechnology Mathematics Physics

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Spatial and Temporal Variability of Sea Surface Height in the Southeastern Tropical Indian Ocean Based on the Satellite Altimeter Data Iskandar, Iskhaq; Mardiansyah, Wijaya; Setiabudidaya, Dedi
Jurnal Matematika dan Sains Vol 19 No 2 (2014)
Publisher : Institut Teknologi Bandung

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Abstract

Sea surface height (SSH) data from merged-satellite observations (e.g. TOPEX/Poseidon, JASON and ERS) were used to evaluate the spatial and temporal variations of sea surface circulations in the southeastern tropical Indian Ocean (SETIO). A Complex Empirical Orthogonal Function (CEOF) was used to extract the dominant mode of variability in the SETIO region. The results show that the first mode accounts for 41.2% of the total variance dominates the variation. The second mode accounts for 18.2% of the total variance, while the third and the fourth modes explain 6.5% and 2.6% of the total variance, respectively. The spectrum analysis indicates that the 35-day variations is a prominent feature in all CEOF modes. Furthermore, semiannual variation at period of about 180-day was observed in the first third modes, while the annual variation of about 300-day was only observed in the first two modes. A relatively strong variation at period of around 500-day was observed in the first, second and fourth modes. It is suggested that the spatial and phase pattern of the first and third modes are related to the propagation of the Kelvin waves generated by wind stress over the equatorial Indian Ocean. On the other hand, the second was likely related to the local upwelling and downwelling generated by the seasonal changes in the alongshore winds. Furthermore, the fourth mode represents the oceanic eddy generated from the downstream straits of the Indonesian Throughflow.Variasi Spasial dan Temporal Tinggi Muka Laut di Wilayah Tropis Samudera India Bagian Tenggara Berdasarkan Data Satelit AltimetriAbstrak Data tinggi permukaan laut hasil observasi dari beberapa satelit (yaitu: TOPEX/Poseidon, JASON dan ERS) digunakan untuk evaluasi variasi spasial dan variasi temporal sirkulasi permukaan laut di wilayah tropis Samudera Hindia bagian tenggara. Analysis dilakukan menggunakan metode Complex Empirical Orthogonal Function (CEOF) untuk mendapatkan mode variasi yang dominan di wilayah ini. Hasil analisis menunjukkan bahwa mode CEOF pertama menjelaskan 41,2% dari variasi total dan merupakan mode yang paling dominan. Mode CEOF kedua mengandung 18,2% dari variasi total, sedangkan mode ketiga dan keempat menjelaskan masing-masing 6,5% dan 2,6% dari variasi total. Analisis spektrum terhadap deret waktu masing-masing mode CEOF menunjukkan bahwa variasi dalam skala 35 hari merupakan variasi yang signifikan untuk setiap mode. Selanjutnya, variasi setengah-tahunan dengan periode osilasi sekitar 180 hari terekam pada tiga mode pertama, sementara variasi tahunan dengan periode osilasi sekitar 300 hari hanya terekam pada mode pertama dan mode kedua. Variasi yang cukup kuat pada periode osilasi sekitar 500 hari terekam pada mode pertama, mode kedua dan mode keempat. Hasil analisis ini juga menunjukkan bahwa pola spasial dan fase gelombang pada mode pertama dan mode ketiga adalah terkait dengan penjalaran gelombang Kelvin yang dibangkitkan oleh stres angin di wilayah ekuator Samudera Hindia. Sementara itu, mode kedua terkait dengan proses upwelling dan downwelling yang dibangkitkan oleh angin muson di sepanjang pantai. Selanjutnya, mode keempat merepresentasikan oceanic eddy yang terbentuk dari selat-selat arus lintas Indonesia (ARLINDO).  Kata kunci: Complex empirical orthogonal function, Analisis Fourier, Samudera Hindia, Tinggi permukaan laut. 
Coupled Ocean-Atmosphere Mode in the Tropical Indian Ocean during 2011 Iskandar, Iskhaq; Mardiansyah, Wijaya; Setiabudidaya, Dedi
Makara Journal of Science Vol. 18, No. 4
Publisher : UI Scholars Hub

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Abstract

Coupled ocean-atmosphere mode in the tropical Indian Ocean, so-called the Indian Ocean Dipole (IOD), occurred
An Updated Water Masses Stratification of Indonesian Maritime Continent (IMC) Attributed to Normal and ENSO Conditions by Argo Float Bahiyah, Amirotul; Wirasatriya, Anindya; Mardiansyah, Wijaya; Iskandar, Iskhaq
Science and Technology Indonesia Vol. 9 No. 2 (2024): April
Publisher : Research Center of Inorganic Materials and Coordination Complexes, FMIPA Universitas Sriwijaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26554/sti.2024.9.2.299-313

Abstract

The tropical area of the Indonesian Maritime Continent (IMC) is frequently regulated by El Niño Southern Oscillation (ENSO), resulting in various water mass stratification in every climate event, such as El Niño and La Niña occurrences. As a consequence, changes in the typical Indonesian Throughflow (ITF) are linked to ENSO circumstances that affect the Indian Ocean. This study used Argo float data to evaluate the change in water mass stratification and vertical density profiles along the main pathway of ITF at each event. However, due to a scarcity of observation data, the comparison study of normal to ENSO occurrences has been limited in the ITF area. In typical circumstances throughout the year, the entrance channel (the western Pacific Ocean, the northern waters of Molucca Island, and the Halmahera Sea) had a higher saline value and cooler water masses than other ITF channels, with a range of roughly 33.5 - 35.5 PSU/13 - 22 ◦C, particularly during the Northwest (NW) Monsoon (December to February or DJF). Unlike the inlet, the Temperature-Salinity (T-S) diagram showed a declining value in both parameters (Celebes Sea, Makassar Strait, and Molucca Sea). Still, the outflow pathway in the Southeastern Tropical Indian Ocean (SETIO) showed a rising T-S diagram. During La Niña events, IMC water masses are often portrayed as fresher and warmer, while reverse circumstances are depicted in El Niño events with exclusion at SETIO station, indicating saltier and colder water masses than normal conditions. An extreme alteration with a large T-S range is mostly depicted in Makassar Strait from Southeast (SE) monsoon (September to November or SON) to NW monsoon, followed by the Banda Sea and then the Molucca Sea.
Spatial-Temporal Analysis of Land Cover Change and Flood Risk Detection in North Musi Rawas District, South Sumatra, Indonesia: Approach Gis and Sentinel Imagery Fitra, Mahturai Rian; Suwignyo, Rujito Agus; Putranto, Dinar DA.; Mardiansyah, Wijaya
Jurnal Locus Penelitian dan Pengabdian Vol. 4 No. 7 (2025): JURNAL LOCUS: Penelitian dan Pengabdian
Publisher : Riviera Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.58344/locus.v4i7.4067

Abstract

This study aims to analyze the dynamics of land cover changes in North Musi Rawas Regency in the period 2017–2023 and triggers for flood risk using remote sensing and Geographic Information Systems (GIS) approaches. The research methods include Sentinel-2 satellite imagery classification using supervised classification techniques, accuracy validation, and spatial-temporal analysis to identify land conversion patterns and their relationship to hydrological dynamics. The results of the analysis show significant conversion of agricultural land vegetation (9,769 ha), built-up land (194 ha), shrubs (15,011 ha), and swamps (514.17 ha), which are driven by urbanization factors, expansion of the agricultural sector, and environmental degradation. These changes contribute to increased flood risk, with the area affected by the medium risk category reaching 133,586 ha, especially in Karang Dapo, Rupit, and Rawas Ilir Districts, while the low-risk area covers 31,397 ha. Meanwhile, areas with better vegetation cover show higher flood mitigation capacity. This study confirms that changes in land cover have a close correlation with increased flood risk, so that land management policies based on spatial data and the use of remote sensing technology are needed to support disaster mitigation and adaptation strategies more effectively
Perbandingan Normalized Difference Vegetation Index Antara Citra Satelit MODIS, Landsat, dan Planet Scope untuk Identifikasi Deforestasi Akibat Pertambangan di Kabupaten Lahat Mulya, Aldi Jati; Mardiansyah, Wijaya; Nur khakim, Mokhamad Yusup
Jurnal Penelitian Sains Vol 27, No 2 (2025)
Publisher : Faculty of Mathtmatics and Natural Sciences

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.56064/jps.v27i2.1206

Abstract

Eksploitasi pertambangan Batubara merupakan salah satu faktor utama yang menyebabkan deforestasi secara masif di Kabupaten Lahat. Untuk menyelaraskan laju deforestasi secara efektif, penelitian ini memanfaatkan data citra satelit dengan resolusi spasial yang berbeda. Tujuan dari penelitian ini adalah untuk membandingkan hasil indeks vegetasi NDVI (Normalized Difference Vegetation Index) dari tiga jenis citra satelit MODIS, Landsat 8, dan PlanetScope guna mendeteksi citra dengan akurasi terbaik dalam mendeteksi deforestasi akibat aktivitas pertambangan. Metodologi yang digunakan meliputi ekstraksi nilai NDVI dari masing-masing citra untuk periode tahun 2020–2024 secara spasial dan temporal, perbandingan nilai NDVI antara MODIS dan Landsat terhadap citra resolusi tinggi PlanetScope menggunakan parameter statistik Root Mean Square Error (RMSE), Mean Absolute Error (MAE), dan koefisien determinasi (R²), serta analisis laju deforestasi citra menggunakan satelit dengan korelasi terbaik terhadap data PlanetScope. Hasil analisis menunjukkan bahwa perbedaan resolusi spasial berpengaruh terhadap nilai akurasi NDVI yang dihasilkan. Citra Landsat memiliki nilai RMSE yang lebih rendah dibandingkan MODIS, yaitu berkisar antara 0,08 hingga 0,14 setiap tahunnya, sedangkan MODIS menunjukkan nilai RMSE antara 0,19 hingga 0,22. Nilai MAE Landsat berada pada kisaran 0,04 hingga 0,08, lebih kecil dibandingkan MAE MODIS yang berkisar antara 0,02 hingga 0,21. Dari hasil koefisien determinasi (R²), Landsat menunjukkan nilai yang lebih tinggi, yaitu antara 0,49 hingga 0,84, sedangkan MODIS hanya mencapai maksimum 0,44. Dengan demikian, citra Landsat dipilih sebagai dasar untuk identifikasi laju deforestasi. Berdasarkan hasil interpretasi NDVI dari citra Landsat, diketahui bahwa laju deforestasi di Kabupaten Lahat selama periode 2020–2024 mencapai sekitar 4% atau seluas 5.859,36 hektar.
Co-Authors Anindya Wirasatriya Bahiyah, Amirotul Dedi Setiabudidaya Fitra, Mahturai Rian Iskhaq Iskandar Mulya, Aldi Jati Nur khakim, Mokhamad Yusup Putranto, Dinar DA. Rujito Agus Suwignyo