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INDENTIFYING PATTERNS OF SATTELITE IMAGERY USING AN ARTIFICIAL NEURAL NETWORK Iskandar, Iskhaq; Affandi, Azhar; Setiabudidaya, Dedi; Irfan, Muhammad; Mardiansyah, Wijaya; Syamsuddin, Fadli
International Journal of Remote Sensing and Earth Sciences (IJReSES) Vol 9, No 1 (2012)
Publisher : National Institute of Aeronautics and Space of Indonesia (LAPAN)

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (620.1 KB) | DOI: 10.30536/j.ijreses.2012.v9.a1824

Abstract

An artificial neural network analysis based on the self-organizing map (SOM)  was used  to  examine  patterns  of  satellite  imagery.  This  study  used  3  ×  4  SOM  array  to  extract patterns  of  satellite-observed  chlorophyll-a  (chl-a)  along  the  southern  coast  of  the  Lesser Sunda Islands from 1998 to 2006. The analyses indicated two characteristic spatial patterns, namely the northwest and the southeast monsoon patterns. The northwest monsoon pattern was characterized by a low  chl-a concentration. In contrast, the southeast monsoon pattern was  indicated  by  a  high  chl-a  distributed  along  the  southern  coast  of  the  Lesser  Sunda Islands.  Furthermore,  this  study  demonstrated  that  the  seasonal  variations  of  those  two patterns  were  related  to  the  variations  of  winds  and  sea  surface  temperature  (SST).  The winds  were  predominantly  southeasterly  (northwesterly)  during  southeast  (northwest) monsoon, drived  offshore (onshore) Ekman transport and  produced  upwelling (downwelling) along  the  southern  coasts  of  the  Lesser  Sunda  Islands.  Consequently,  upwelling  reduce dSST  and  helped  replenish  the  surface  water  nutrients,  thus  supporting  high  chl-a concentration. Finally, this study demonstrated that the SOM method was very useful for the identifications of patterns in various satellite imageries.
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. 
Analisis Dinamika dan Sumber Massa Air Arus Lintas Indonesia Mardiansyah, Wijaya
Jurnal Penelitian Sains No 15 (2004)
Publisher : Faculty of Mathtmatics and Natural Sciences

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Abstract

Dalam penelitian ini dilakukan pengkajian dinamika massa air Arus Lintas Indonesia (Arlindo) dalam kaitannya dengan sumber asli air yang dapat teridentifikasi masuk dari Samudra Pasifik ke perairan Indonesia Bagian Timur. Wilayah studi berada pada 12.5° LU – 2.5° LS dan 122,5° BT - 140° BT. Sumber data adalah World Ocean Database 2001 dari National Oceanography Data Center (NODC), http://www.nadc.noaa.gov/PC5/WODo1/pacif_o.html. Analisis dilakukan dengan menggunakan metode core layer dan analisis isopiknal sedangkan untuk mengolah dan menampilkan data digunakan software Ocean Data View mp versi 1.2, http://www.awi-bremerhaven.de/GEO/odv.Dari analisis yang dilakukan teridentifikasi bahwa sumber air Arlindo yang masuk ke Perairan Indonesia bagian timur melalui gerbang Arlindo memiliki karakteristik dari berbagai massa air, antara lain adalah core dari; NPSW dengan densitas potensial sekitar 24 sq salinitas 34.76<S<35 psu, dan konsentrasi oksigen terlarut >4 ml/l; SPSW dengan densitas potensial ekitar 25 sq salinitas S>35 psu dan konsentrasi oksigen terlarut sekitar 3.3 ml/l; NPIW dengan densitas potensial 26.5 sq salinitas S<34.55 psu dan konsentrasi oksigen terlarut antara 2 -3 ml/l dan  AAIW dengan densitas potensial sekitar 27.2 sq. Secara umum semua karakteristik massa air ini mengidentifikasikan bahwasanya sumber air Arlindo berasal dari Samudera Pasifik.
Analisis Terhadap Korelasi Antara Jumlah Curah Hujan dan Temperatur Udara Irfan, Muhammad; Mardiansyah, Wijaya; Alhadi, Yudi
Jurnal Penelitian Sains No 17 (2005)
Publisher : Faculty of Mathtmatics and Natural Sciences

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Abstract

Telah dilakukan penelitian untuk mencari korelasi empirik antara jumlah curah hujan dengan temparatur udara. Data yang digunakan adalah data curah hujan bulanan dan temperatur udara bulanan periode tahun 1994-2003 untuk wilayah Kenten dan wilayah Bandara Sultan Mahmud Badaruddin II. Metoda yang dilakukan adalah dengan membuat grafis korelasi antara jumlah curah hujan bulan dengan temperatur bulanan, menganalisis grafik yang dihasilkan, dan membahas secara teori tentang kebenaran hasil yang didapat. Penelitian ini telah menunjukkan bahwa adanya korelasi yang kurang signifikan antara jumlah curah hujan dan temperatur udara, dimana semakin tinggi temperatur udara maka semakin rendah jumlah curah hujan dan sebaliknya.
On the Influence of Enso And IOD on Rainfall Variability Over The Musi Basin, South Sumatra Mardiansyah, Wijaya; Setiabudidaya, Dedi; Khakim, M. Yusup Nur; Yustian, Indra; Dahlan, Zulkifli; Iskandar, Iskhaq
Science and Technology Indonesia Vol 3 No 4 (2018): October
Publisher : ARTS Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (4342.559 KB) | DOI: 10.26554/sti.2018.3.4.157-163

Abstract

The southern Sumatera region experiences one rainy season and one dry season in a year associated with seasonal change in monsoonal winds. The peak of rainy season is occurring in November-December-January during the northwest monsoon season, while the dry season comes in June-July-August during the southeast monsoon season. This study is designed to evaluate possible influence of the coupled ocean-atmospheric modes in the tropical Indo-Pacific region, namely the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) on the rainfall variability over the catchment area of the Music Basin, South Sumatera. The ENSO and IOD occurrences were reflected by the variability of sea surface temperature (SST) in the tropical Pacific and Indian Ocean, respectively. During El Niño and/or positive IOD episode, negative SST anomalies cover the eastern tropical Indian Ocean and western tropical Pacific including the Indonesian seas, leading to suppress convective activities that result in reduce precipitation over the maritime continent. The situation is reversed during La Niña and/or negative IOD event. The results revealed that the high topography area (e.g. Bukit Barisan) was shown to be instrumental to the pattern of rainfall variability. During the 2010 negative IOD co-occurring with La Niña event, the rainfall was significantly increase over the region. This excess rainfall was associated with warm SST anomaly over the eastern tropical Indian Ocean and the Indonesian seas. On the other hand, extreme drought event tends to occur during the 2015 positive IOD simultaneously with the occurrence of the El Niño events Investigation on the SST patterns revealed that cold SST anomalies covered the Indonesian seas during the peak phase of the 2015 positive IOD and El Niño event.