Wijaya Mardiansyah

Normal.dotm 0 0 1 214 1220 University of Sriwijaya 10 2 1498 12.0 0 false 18 pt 18 pt 0 0 false false false 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 Altimetri Abstrak 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.

Karimata Strait is a vast strait which connecting the South China Sea to the Java Sea and has a geostrategic function. This study aims to determine oceanographic characteristics in the Karimata Strait which includes wave, current and tidal conditions. The data used is derived from National Oceanic and Atmospheric Administration (NOAA) and Babel Ocean Observation Science and Technologies Centre (BOOST CENTRE). This research is focused on oceanographic conditions in the eastern monsoon (August 2017). The analysis shows the current direction in the Karimata Strait has speed between 0 – 0.25 m/s to the northwest. The wave height in the southern waters of the Karimata Strait tends to be higher between 0.175 – 0.225 m. Furthermore, the tides in Karimata Strait has a diurnal type with formzahl numbers is F=12.33 and tidal mounts is 2m.

The existence of the Indonesian government's One Map Policy (OMP) demands synergy to the regions. Sumatra is one of the areas that captures this opportunity. One of the follow-up actions to this policy is regional readiness in preparing qualified human resources in the geospatial field. Sriwijaya University as one of the universities in Indonesia that focuses on developing human resources in South Sumatra, facilitates local governments in developing employee capacity. This program was carried out for 5 days to learn about the basic level Geographic Information System (GIS) for Bappeda Lahat employees. This program is carried out in 3 stages, namely identification of partner problems, training, and evaluation. This training program has a positive impact on employees in Bappeda Lahat, namely being able to make location points for regional planning with SmartGPS, making spatial shapefile data and making thematic spatial maps according to the main tasks of the job fields of employee...

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 s q salinitas 34.76 4 ml/l; SPSW dengan densitas potensial ekitar 25 s q salinitas S>3...

Subsurface chlorophyll-a (chl-a) concentration variability on Sumatera’s Northwestern coast is part of the phytoplankton biomass that supports and enriches the region’s fisheries supplies. During the 2017 northeast monsoon season from 25th November 25 to 11th December, the Ekspedisi Widya Nusantara (E-WIN) collected data from 16 stations. The finding demonstrates a rise in subsurface chl-a concentration as you get closer to the coast. Furthermore, the deep chl-a maximum (DCM) is only found offshore, with depths−3 between 30 to 50 m and chl-a concentrations of 0.07 to 0.25 mg.m. Surface chl-a concentrations near the coast were found to be high, ranging from 0.2 to 0.25 mg.m-3

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 ...

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...

Karimata Strait is a vast strait which connecting the South China Sea to the Java Sea and has a geostrategic function. This study aims to determine oceanographic characteristics in the Karimata Strait which includes wave, current and tidal conditions. The data used is derived from National Oceanic and Atmospheric Administration (NOAA) and Babel Ocean Observation Science and Technologies Centre (BOOST CENTRE). This research is focused on oceanographic conditions in the eastern monsoon (August 2017). The analysis shows the current direction in the Karimata Strait has speed between 0 – 0.25 m/s to the northwest. The wave height in the southern waters of the Karimata Strait tends to be higher between 0.175 – 0.225 m. Furthermore, the tides in Karimata Strait has a diurnal type with formzahl numbers is F=12.33 and tidal mounts is 2m.

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.

Normal.dotm 0 0 1 214 1220 University of Sriwijaya 10 2 1498 12.0 0 false 18 pt 18 pt 0 0 false false false 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 fi...

The peak time of rainfall occurrence over an area has certain characteristics in which the difference in time and intensity of rainfall varies depending on its location and distance from the sea. This variation can be determined based on the phase and amplitude obtained using harmonic analysis. In this study, combined data from in-situ observation, satellite remote sensing and reanalysis were used to analyze spatial and temporal variations of peak rainfall events over peatland area of the South Sumatra Province. The results show that most of the South Sumatra Province has a diurnal peak of rainfall during afternoon ranging from 16.00 to 19.00 Western Indonesian Time. In addition, the results also indicate that the analysis on the in situ data revealed seasonal variation both in amplitude and time of maximum diurnal rainfall, while the reanalysis data only indicated a weak seasonal variation on the amplitude of the diurnal rainfall. Furthermore, spatial analysis shows that the time o...

The Indonesian sea is the only low-latitude pathway connecting two tropical oceans, which plays an important role in the coupled ocean-atmosphere mode in the Indo-Pacific sector. A small change in the sea surface temperature (SST) in the Indonesian sea has a significant influence on the precipitation and air-sea heat flux. During the past 33 years, the SST in the Indonesian sea has indicated a warming trend on the average of 0.19 ± 0.04 decade−1, which is larger than global SST warming trend. Moreover, the warming trend indicates seasonal variations, in which maximum trend occurred during boreal summer season. Investigation on the potential driver for this warming trend, namely, the net surface heat flux, resulted in an opposite trend (cooling trend), while the Ekman pumping and the wind mixing only play a minor role on the SST warming. Here, we proposed the upper layer process associated with an increasing trend in precipitation and decreasing trend in mixed layer depth (MLD) for t...

An integrated observation system, so-called SEnsory data transmission Service Assisted by Midori Engineering laboratory (SESAME) has been deployed to measure hydrological and climatological parameters at peatlands of South Sumatera since June 2017. One of the observed hydrological parameters is the Ground Water Level (GWL). This study evaluates the spatio-temporal variability of GWL observed at 4 locations, namely, Peat Hydrology Unit (PHU) Sungai Saleh 1 (SS1), Sungai Saleh 2 (SS2), Sungai Lumpur 1 (SL1), and Sungai Lumpur 2 (SL2). The data covered a period of July 1, 2017 to June 30, 2018. This study focused on analyzing types of observed tides at each SESAME location. It was found that at the study location SL2, SS1, and SS2 the tidal type was a mixed tide prevailing diurnal. On the other hand, the observed GWL at the SL1 was dominated by a mixed tide prevailing semidiurnal. Further analysis on the observed GWL indicates that the lowest GWL was observed in period September-Octobe...

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 resul...

Spatial and temporal variations of sea surface (SST) in the Banda Sea are studied for the period of June 2002 – May 2008. An empirical orthogonal function (EOF) analysis has been applied to an optimum interpolation SST (OISST) having spatial resolution of 0.25° and temporal resolution of 1 day. The results revealed that the four EOF modes account for 53.1% of the total SST variance. The first EOF mode, which accounts for 33.2% of the total variance, revealed the east-west SST pattern in the Banda Sea. This indicates 180° out of phase temporal variability between the eastern and the western parts of the Banda Sea. The second and the fourth modes explain 9.6% and 4.6% of the total variance respectively. Both two modes show the southeast-northwest spatial pattern. Meanwhile, the third mode accounting for 5.4% of the total variance indicates that the high SST variation is concentrated in the central Banda Sea. In addition, the corresponding principal component time series of the first mode revealed robust sea...

Temporal variability of the Indonesian Throughflow (ITF) in the Timor Passage was evaluated with special focus on its interannual variation. The ITF transport was estimated as a latitudinal averaged of an along strait currents in the Timor Passage based on the output of Simple Ocean Data Assimilation (SODA) experiment from 1958 – 2008. A Complex Empirical Orthogonal Function (CEOF), then, was applied to the interannual estimated ITF transport to extract the dominant mode of variability. The result has shown that the leading CEOF mode was explaining 67.2% of the total interannual variation. The reconstructed first CEOF time series shows strong positive anomalies (towards the Pacific Ocean) during 1962 – 1969, 1972 – 1978, 1997 – 1999, 2002 – 2005 and 2007. The transport was reversed (towards the Indian Ocean) during other periods. The upper layer transport above ∼200m depth is significantly correlated with the zonal wind stress in the western equatorial Pacific Ocean, with the transport lagging the winds by about 10 months. The middle layer transport between about 200 – 600m depth is significantly influenced by the zonal wind from the eastern equatorial Indian Ocean in which the zonal winds lag the ITF by about 5 months. In addition, the deeper layer transport below about 600m depth shows significant zero lag correlation with the zonal wind stress in the western equatorial Pacific Ocean, though the impact of the equatorial Indian Ocean zonal wind stress is not negligible.

Interaksi laut dan atmosfer baik secara lokal, regional maupun global sangat mempengaruhi variasi temporal arus Wyrtki yang terjadi pada arus permukaan ekuator Samudera Hindia yang bergerak ke arah timur. Kajian ini difokuskan pada variasi musiman dan variasi antar-tahunan (interannual) yang dihubungkan dengan fenomena Indian Ocean Dipole (IOD). Analisis dilakukan dengan menggunakan data Ocean Surface Current Analysis-Real time (OSCAR) Project. Hasil penelitian menunjukkan bahwa arus Wyrtki musim peralihan II (Oktober – November) lebih kuat dan berlangsung lebih lama jika dibandingkan dengan arus Wyrtki musim peralihan I. Arus Wyrtki musim peralihan II membentang di sepanjang ekuator dari bujur 50oBT hingga sisi timur Samudera Hindia. Sementara itu, arus Wyrtki musim peralihan I terkonsentrasi di sisi timur Samudera Hindia. Dalam skala antar-tahunan, arus Wyrtki musim peralihan II termodulasi oleh fenomena IOD. Pada kejadian IOD positif, arus Wyrtki musim peralihan II mengalami pelemahan atau bahkan berbalik arah, sementara pada kejadian IOD negatif arus Wyrtki musim peralihan II mengalami peningkatan intensitas. Pola dan amplitudo arus Wyrtki sangat dipengaruhi oleh pola dan amplitudo angin baratan di atas ekuator Samudera Hindia. Angin baratan pada musim peralihan II lebih kuat dan berlangsung lebih lama dibandingkan dengan angin baratan musim peralihan I. Lebih lanjut lagi, ketika terjadi IOD positif di ekuator Samudera Hindia terdapat angin timuran selama musim peralihan II, sedangkan pada saat IOD negatif angin baratan mengalami peningkatan intensitas