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Study of Ocean Climate Variability (1959-2002) in the Eastern Indian Ocean, Java Sea, and Sunda Strait Using the HAMburg Shelf Ocean Model April 21, 2006

Posted by Putri in Penelitian.
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Disertasi lengkap dapat di'download' dari Perpustakaan Universitas Hamburg (Full disertation at Library of Hamburg University)

Abstract

The Indonesian waters, located in the tropical area between the Pacific and Indian Oceans, comprise shelf and deep sea areas with their special characteristics. The Java Sea, as one of the shallow waters areas in Indonesia, has an average depth of about 40m, low salinity and high temperature. South of Java is the deep eastern Indian Ocean which is characterized by high salinity and low temperature. Both water masses are interacting and mixing through the Sunda Strait. Although the Sunda Strait is a small passage, its role in influencing the ocean climate variability is quite important and will be discussed as the main topic in this study.

The HAMburg Shelf Ocean Model (HAMSOM) is used to simulate the long period ocean-climate dynamics in the Java Sea and the eastern Indian Ocean. Numerous simulations and boundary treatments are performed to get results that best agree with the observations. Forcing data from 44 years (1959-2002) NCEP reanalysis are used in the simulation to analyze the variability of current circulation, water mass transport, upwelling south of Java, and the effect of ENSO (in the Pacific Ocean) and DME (in the Indian Ocean) to this area, as well as their interaction.

The seasonal variation in the Java Sea is mainly influenced by the monsoon. In January, representing the NW monsoon situation, water from the Southeast China Sea is transported to the Java Sea by (+)2.1Sv and flows out to the eastern part of the Java Sea and the Sunda Strait by (-)1.6Sv and (-)0.5Sv, respectively. In the contrary, in August (representing the SE monsoon situation), the total inflow to the Java Sea from the eastern part of the Java Sea is 1.0Sv and the water flows out to the Southeast China Sea and the Sunda Strait by (-)0.3Sv and (-)0.7Sv respectively. The SST is increased from 28°C during the NW monsoon to 28.5-29°C during the SE monsoon while the SSS is decreased from 32.6psu to 32.2psu. During the whole year, the water mass is transported from the Java Sea to the Indian Ocean through the Sunda Strait with variations of transport between 0.48Sv (minimum) in December and 0.72Sv (maximum) in August/September. The zonal wind during the SE monsoon is the important factor for triggering and propagating the upwelling south of Java. Normally, the upwelling causes the upwards of temperature lower than 24°C (the peak in August) and salinity higher than 34.4psu (the peak in October).

The DME and ENSO have influence significantly the variability in the study area. Nevertheless, the strengths of their influence are controlled by the strength of the zonal wind in the eastern Indian Ocean, especially during the SE monsoon. The temperature decreases (increases) during the El Nino (La Nina) years when the zonal wind is stronger (weaker) and reversely the salinity increases (decreases) during the El Nino (La Nina). The strong influence of the DME and ENSO can be identified by the SST/SSS anomaly in the study area when they have the same phase as the strengthening zonal wind. Likewise, the strength of upwelling south of Java depends on the strength of SE wind along the south of Java and its interaction with DME and ENSO events. Under normal conditions, the upwelling causes negative SST and positive SSS anomalies 0.3-0.6°C and 0.2-0.3psu, respectively. In the El Nino (La Nina) years, the anomaly of SST and SSS become lower than -1.0°C and higher than 0.3psu (+1.0°C and -0.3psu), respectively.

During the normal years, the variation of SST and SSS anomalies in the Java Sea are about 0.5°C and 0.2psu, respectively. The SST decrease (SSS increase) during the DME and El Nino events because of the transport of water mass with cooler SST (higher SSS) from the eastern Java Sea, while during the La Nina events, the SST increase (SSS decrease) because of the transport of water mass with warmer SST (lower SSS) from the eastern Java Sea. The water mass is still transported through the Sunda Strait from the Java Sea, increased by 0.15-0.2Sv during the El Nino and DME years and decreased by 0.1Sv during the La Nina years.

Bathi Tan444401 Tsan000806

Komentar»

1. kandaga - April 22, 2006

Ibu/Mbak Yaya,

Disertasi yg sangat bagus, dan menarik.
Saya ada beberapa pertanyaan, mohon dijawab ya kalo ada waktu.

Mbak Yaya : “The SST is increased from 28°C during the NW monsoon to 28.5-29°C during the SE monsoon while the SSS is decreased from 32.6psu to 32.2psu”

1. Kenapa SST naik ya mbak. Bukannya sebaliknya ? Begitu juga halnya salinitas, kenapa turun ya ?
Kalo kondisinya SST naik dan SSS turun mekanisme “salt plug” di selat Makassar jadinya nggak jalan mbak. Sedikit pemahaman saya, bukankah di musim barat arus dgn salinitas rendah dari Jawa bergerak ke timur sehingga membuat gradien tekanan antara selat makassar (selatan) dan hindia (negative gradien) yg menyebabkan gelontoran air panas di upper layer (termoklin ke atas) dari pasifik ke hindia “terhambat”. Kemudian, pada SE monsoon angin timur menggerakan arus dari banda dgn salinitas tinggi sehingga menyebabkan gradien tekanan menjadi netral yg pada akhirnya membuka “salt plug” tadi agar air panas dari pasifik menggelontor bebas lagi.

Mbak Yaya: “The zonal wind during the SE monsoon is the important factor for triggering and propagating the upwelling south of Java”
2. Kata triggering, saya mengerti. Tapi propagating saya kurang mengerti. Apakah konteks variabilitas bulanan dari SE monsoon yg menyebabkan fenomena propagating atau bagaimana ? mohon penjelasan dinamika forcing yg menyebabkan adanya propagating.

Mbak Yaya :”The temperature decreases (increases) during the El Nino (La Nina) years when the zonal wind is stronger (weaker) and reversely the salinity increases (decreases) during the El Nino (La Nina)”.

3. Pernyataan diatas mendukung teori salt plug yg sebelumnya saya sebutkan. Pada saat elnino, temperatur di eastern india jadi dingin krn suplai air panas dari pasifik kurang. Ini analog dgn salt plug tadi.
Pertanyaan saya, kenapa zonal wind stronger pada saat temperatur dingin ? bukankah dgn menjadi dingin maka konveksi panas dari laut ke atmosfer menjadi lebih kecil sehingga high pressure di timur hindia menjadi melemah, dan gradien tekanan di atmospere antara timur barat menjadi lebih kecil yg pada akhirnya menyebabkan zonal wind menjadi melemah ?

4. Untuk gambar Anomali SST, itu untuk anomali seasonal, annual, decadal atau ?

5.Apa forcing2 seperti MJO & kelvin waves dimasukan ?

Sekian dahulu, Mbak. Hatur nuhun sebelumnya…

kandaga

2. putri - April 22, 2006

Pertanyaannya banyak amat ya😀 Berarti abstract nya kurang mudah dimengerti ya. Makasih inputnya. Jawabannya nanti saya posting tersendiri ya sekalian ama gambar-gambar detailnya. Bisa jadi bahan diskusi kita.

Itu kalau bisa saya jawab ya hehe… masih banyak faktor yang belum masuk dan (baru tahu sekarang) kekurangan-kekurangan Modelnya dan sekarang sedang saya kembangkan lebih lanjut. Kalau saya gak bisa jawab ya… mungkin ada teman-teman lain yang bisa bantuin nanti. Atau barangkali Kandaga berminat bikin artikel lain mengenai teori diatas? Boleh lho… ditunggu banget.

btw.. gambar-gambar yang dibawah itu cuma contoh aja. Lintasan AB bukan di laut Jawa. Anomali-anomali yang saya buat disini bulanan (monthly) selama 44 tahun. Ada banyak perbedaan yang terjadi di Laut Jawa dan di selatan Jawa saat tahun 1972, 1982, 1987, dan 1997 yang ‘sama-sama’ dikatakan tahun kejadian El Nino ‘kuat’ terjadi di Pasific, juga saat La Nina, demikian juga perbedaan saat tahun-tahun dimana ada Dipole Mode ‘kuat’ di Samudra Hindia.

Insya Allah nanti malam ya… mau ke mesjid dulu, mau ada lomba utnuk anak-anak dalam rangka memperingati Maulid Nabi di Mesjid Indonesia, Hamburg.

Sekali lagi makasih…

3. kandaga - April 22, 2006

He..he,
Banyak pertanyaannya karena saya benar2 baru dan lagi senang sama yang beginiian Mbak. Seringkali, saya konsep nya terbalik2.
Jadi menggelontorlah pertanyaan…

Btw, senang dengan ada blog seperti ini yg jadi sumber ilmu.

4. Lautanku » Sedikit tentang HAMSOM - April 23, 2006

[…] Untuk mendiskusikan pertanyaan-pertanyaan ini dari Kandaga, terlebih dahulu saya mencoba mengulas sedikit tentang HAMSOM, model yang saya gunakan dalam mengerjakan disertasi tersebut. Semoga bermanfaat juga bagi teman-teman yang berminat melamar kesempatan Open Position tahun ini. […]

5. jailani - September 15, 2006

Mohon bantuan untuk menjelaskan tentang termoklin, apa variabel yang mempengaruhi termoklin, apakah suhu air laut lebih dominan atau kedalaman dalam penentuan termoklin. Mba ngreti kasus newmont dibuyat. apa pendapat mba.???

6. Fajri - Januari 7, 2007

Mohon bantuan juga mba, mau tanya bagaimana variabilita/variasi termoklin di selat makassar bila dihubungkan ENSO dan dengan kedalamannya???

matur nuwun ya mbak
salam kenal, nama saya Fajri Dwihasta


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