Analisis Spatial Extreme Value pada Curah Hujan Ekstrem dengan Proses Extremal-t

Nuroini, Husna Mir'atin (2023) Analisis Spatial Extreme Value pada Curah Hujan Ekstrem dengan Proses Extremal-t. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Kondisi topografi di Indonesia terdiri dari pantai, dataran rendah, dataran tinggi, hingga pegunungan. Hal itu menyebabkan wilayahnya memiliki keragaman cuaca dan iklim yang tinggi, sehingga memungkinkan terjadinya fenomena hidrologi seperti curah hujan ekstrem, angin topan, suhu tinggi, dan badai. Akhir-akhir ini, pemanasan global menjadi isu lingkungan yang marak diperbincangkan. Salah satu dampaknya adalah perubahan iklim yang berpengaruh pada terjadinya fenomena hidrologi ekstrem dan berpotensi mengakibatkan banjir, mengganggu transportasi dan komunikasi, merusak infrastruktur, merugikan sektor pertanian, hingga mengancam kehidupan. Oleh karena itu, penelitian ini bertujuan untuk mendapatkan model terbaik dan return level curah hujan ekstrem di Kabupaten Ngawi tahun 1990 – 2014 melalui Spatial Extreme Value (SEV) dengan metode Max-Stable Processes (MSP) menggunakan proses extremal-t. Estimasi parameter yang digunakan adalah Maximum Likelihood Estimation (MLE) dan Maximum Pairwise Likelihood Estimation (MPLE), kemudian diselesaikan dengan metode iterasi numerik Broyden-Fletcher-Goldfarb-Shanno (BFGS) Quasi-Newton dan Nelder-Mead. Berdasarkan hasil analisis yang telah dilakukan, diperoleh model trend surface terbaik melalui iterasi Nelder-Mead dengan rata-rata curah hujan yang dipengaruhi oleh garis bujur (longitude). Sedangkan variansi dan bentuk distribusi curah hujan tidak dipengaruhi oleh garis lintang ataupun bujur. Hal tersebut disinyalir karena lokasi stasiun pengamatan terletak dalam ZOM yang sama, sehingga bersifat homogen. Selain itu, hasil prediksi return level mempunyai akurasi yang lebih baik apabila digunakan dalam periode 1 tahun. Namun, mengalami penurunan seiring dengan bertambahnya periode.
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The topographical conditions in Indonesia consist of coasts, lowlands, highlands, and mountains. This causes the area to have a high diversity of weather and climate, enabling several hydrological phenomena such as extreme rainfall, hurricanes, high temperatures, and storms. Nowadays, global warming has become a widely discussed environmental issue. One of its impacts is climate change, which affects the occurrence of extreme hydrological phenomena and potentially causes floods, disruption of transportation and communication, damage to infrastructure, harm to the agricultural sector, and threat to life. Therefore, this study aims to obtain the best model and return level of extreme rainfall in Ngawi Regency from 1990 to 2014 through Spatial Extreme Value (SEV) using Max-Stable Processes (MSP) method with the extremal-t process. The estimation parameters used are Maximum Likelihood Estimation (MLE) and Maximum Pairwise Likelihood Estimation (MPLE), then solved by Broyden-Fletcher-Goldfarb-Shanno (BFGS) Quasi-Newton and Nelder-Mead numerical iteration methods. Based on the analysis result, the best trend surface model is obtained through Nelder-Mead iteration with the average rainfall influenced by longitude. Whereas variance and shape of rainfall distribution are not affected by longitude or latitude. It is supposed as the observation stations are located in the same ZOM, so it is homogeneous. In addition, the return level prediction results have better accuracy when used in 1 year. However, it decreases as the period increases.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	Curah Hujan Ekstrem, Maximum Likelihood Estimation, Max-Stable Processes, Proses Extremal-t, Return Level, Extremal-t Process, Extreme Rainfall, Maximum Likelihood Estimation, Max-Stable Processes, Return Level
Subjects:	H Social Sciences > HA Statistics > HA30.6 Spatial analysis Q Science > QA Mathematics
Divisions:	Faculty of Mathematics and Science > Statistics > 49101-(S2) Master Thesis
Depositing User:	Husna Mir'atin Nuroini
Date Deposited:	20 Feb 2023 02:56
Last Modified:	20 Feb 2023 02:56
URI:	http://repository.its.ac.id/id/eprint/97590

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