Judul: Variability of Chlorophyll-a Concentration and Sea Surface Temperature in the Western Java Sea Using MODIS Satellite Data on Fish Catches
Abstrak: Konsentrasi klorofil-a (Chl-a) dan Suhu Permukaan Laut (SPL) adalah parameter penting yang berpengaruh terhadap keberadaan sumberdaya ikan. Tujuan penelitian ini adalah menganalisis variabilitas konsentrasi klorofil-a dan SPL dari satelit Moderate Resolution Maging Spectroradiometer (MODIS), serta hasil tangkapan ikan di Perairan Laut Jawa bagian barat. Selain itu data pendukung lainnya berupa El Nino Southern Oscillation (ENSO) bulanan dan Indeks Dipole Mode (DMI) bulanan juga digunakan dalam peneltiian ini. Penelitian ini dilaksanakan pada bulan Desember 2021-Juli 2022 di Perairan Laut Jawa bagian barat. Data SPL dan klorofil-a dianalisis berdasarkan data rata-rata bulanan dari hasil estimasi satelitMODIS selama 12 tahun (Januari 2010-Desember 2021). Hasil penelitian menunjukkan nilai konsentrasi klorofil-a berada dikisaran 0.42 mg/m³–1.55 mg/m³ yang mengalami peningkatan pada musim barat dan timur serta mengalami penurunan pada musim peralihan 1 dan 2. Nilai SPL berada dikisaran 29.05°C-30.71°C dan mengalami peningkatan saat musim peralihan 1 dan 2 yang dipengaruhi oleh peningkatan intensitas radiasi matahari dan pergerakkan massa air dari Timur Laut menuju Barat Daya. Variabilitas SPL dan klorofil-a memiliki kecenderungan terhadap hasil tangkapan ikan tembang di Perairan Laut Jawa bagian barat dan sekitarnya. Pada saat fenomena La Nina (ENSO Indeks positif) dan Dipole Mode Index bernilai negatif terjadi secara bersamaan, nilai klorofil-a relatif lebih tinggi dari normalnya dan nilai SPL relatif lebih rendah dari normalnya., Concentration of chlorophyll-a (Chl-a) and sea surface temperature (SST) are important parameters that affect the existence of fish resources. The purpose of this study was to analyze the variability of chlorophyll-a concentrations and SST from the Moderate Resolution Maging Spectroradiometer (MODIS) satellite, as well as fish catches in the western Java Sea. In addition, other supporting data in the form of monthly El Nino Southern Oscillation (ENSO) and monthly Dipole Mode Index (DMI) are also used in this study. This research was carried out in December 2021-July 2022 in the western part of the Java Sea. SST and chlorophyll-a data were analyzed based on monthly average data from the estimation results of the MODIS satellite for 12 years (January 2010-December 2021). The results showed that the concentration of chlorophyll-a was in the range of 0.42 mg/m³–1.55 mg/m³ which increased in the west and east monsoons and decreased in transition seasons 1 and 2. SST values were in the range of 29.05°C-30.71°C and experienced increase during transitional seasons 1 and 2 which are influenced by increased intensity of solar radiation and movement of water masses from the Northeast to the Southwest. The variability of SST and chlorophyll-a has a tendency to catch tembang fish in the western Java Sea and its surroundings. When the La Nina phenomenon (positive ENSO Index) and negative Dipole Mode Index occur simultaneously, the chlorophyll-a value is relatively higher than normal and the SST value is relatively lower than normal.
Keyword: Klorofil-a, Musim, Suhu Permukaan Laut, Chlorophyll-a, Season, Sea Surface Temperature

Judul: Variabilitas Suhu Permukaan Laut dan Konsentrasi Klorofil-a di Samudera Hindia Bagian Timur Laut Sebelah Barat Sumatera
Abstrak: Suhu Permukaan Laut (SPL) dan konsentrasi klorofil-a merupakan parameter penting di dalam suatu perairan dan memiliki kaitan erat terhadap terjadinya fenomena oseanografi dan tingkat produktifitas. Tujuan penelitian ini adalah menganalisis variabilitas SPL dan konsentrasi klorofil-a di Sekitar Samudera Hindia bagian Timur Laut sebelah barat Sumatera. Penelitian ini menggunakan gabungan data citra NOAA-AVHRR dan MODIS untuk SPL, data citra SeaWiFS dan MODIS untuk klorofil-a, data angin permukaan bulanan diperoleh dari European Centre for Medium-Range Weather Forecasts (ECMWF). Data pendukung berupa indeks El Nino Southern Oscillation (ENSO) bulanan diperoleh dari laman https://www.ncdc.noaa.gov/teleconnections/ enso/indicators/ soi/ dan Dipole Mode Index (DMI) bulanan diperoleh dari laman https://www. jamstec.go.jp/virtualearth/general/en/index.html. Hasil penelitian menunjukkan bahwa SPL di daerah penelitian selama 22 tahun (1997–2019) berada pada kisaran 29,30 °C–31,60 °C dengan rata-rata 29,35 °C. Nilai SPL yang lebih tinggi terjadi saat Musim Barat sampai Musim Peralihan-1, sementara nilai yang lebih rendah pada Musim Timur sampai Musim Peralihan-2. Variabilitas nilai SPL dipengaruhi oleh pola angin musiman, intensitas radiasi matahari, dan Indian Ocean Dipole Mode (IODM). Saat IOD Negatif menyebabkan nilai SPL yang lebih tinggi dan konsentrasi Chl-a lebih rendah dari biasanya. Konsentrasi klorofil-a selama 22 tahun berkisar antara 0,0757 mg/m3–1,3006 mg/m3, konsentrasi klorofil-a yang lebih tinggi terjadi saat akhir Musim Timur (Agustus) dan awal Musim Barat (Desember), sementara nilai yang lebih rendah saat Musim Peralihan-1. Tingginya SPL berkisar pada Musim Peralihan-1 (Maret–Mei) bersamaan dengan rendahnya Chl-a pada musim yang sama diduga akibat terjadinya fenomena IOD negatif. Variabilitas Chl-a dipengaruhi oleh pola angin musiman, pergerakan massa air, dan IOD. Secara spasial konsentrasi Chl-a lebih tinggi didaerah pesisir dibandingkan di lepas pantai. Fenomena IOD mempengaruhi pola variasi interannual SPL dan konsentrasi Chl-a., Sea Surface Temperature (SST) and chlorophyll-a concentration are important parameters in waters that have an influence on oceanographic phenomena and oceanic productivity. The objective of this study was to analyze the variability of SST and chlorophyll-a concentration in the Northeast Indian Ocean off the West of Sumatra. The study used a combination of NOAA-AVHRR and MODIS image data for SST, SeaWiFS and MODIS image data for chlorophyll-a concenration, monthly surface wind data from the European Center for Medium Range Weather Forecasts (ECMWF). Supporting Data such as the monthly El Nino Southern Oscillation (ENSO) index and the Dipole Mode Index (DMI) were obtained from the web page of https://www.ncdc.noaa.gov/teleconnections/enso/ indicators/soi/ and https://www.jamstec.go.jp/virtualearth/general/en/index.html, respectively. The results showed that the range of SST during a 22 year period (1997–2019) was 29,30 °C–31,60 °C with the average of 29,35 °C where the higher SST occurred during the West Season and Transition Season 1, while the lower values were found during the East Season and Transition Season 2. variability of the SST values was related to the influence of seasonal winds, the intensity of solar radiation, and Indian Ocean Dipole Mode (IODM). When Negative IOD causing higher SST and lower Chl-a concentration than normal. Chlorophyll-a concentration for a 22 year perioed ranged of 0,0757-1,3006 mg/m3 where higher chlorophyll-a concentration occurred from the end of East Season (August) to the early of West Season (December), while lower values were found during Transition Season 1. The evidence of higher
Keyword: ENSO, IODM, Chlorophyll-a, Sea Surface Temperature

Judul: Truncated Stop Loss as a Optimal Solution of Reinsurance Agreement in One-Period Model
Abstrak: Reinsurance is one of risk management efforts of an insurance company, which is called the cedent. Similar with insurance, reinsurance constitutes the cedent to pay the premium. We consider one-period reinsurance model and derive a rule which minimizes the ruin probability of the cedent for a fixed reinsurance premium. Therefore, it is needed to construct an optimal reinsurance agreement for the cedent. The premium is calculated according to four different principles, i.e. economic, generalized zero-utility, Esscher, and mean-variance principles. Stop loss is a reinsurance contract which protect the insurance company for losses that exceed a certain amount. The result of this research shows that a truncated stop loss is an optimal agreement in the class of all reinsurance contracts with various premiums calculated using above mentioned principles.
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