ANALISIS POLA CURAH HUJAN TAHUNAN DAN ANTAR TAHUNAN DI WILAYAH INDONESIA MENGGUNAKAN EMPIRICAL ORTHOGONAL FUNCTION (EOF)

ARISKA, MELLY and Iskandar, Iskhaq and Irfan, Muhammad (2025) ANALISIS POLA CURAH HUJAN TAHUNAN DAN ANTAR TAHUNAN DI WILAYAH INDONESIA MENGGUNAKAN EMPIRICAL ORTHOGONAL FUNCTION (EOF). Doctoral thesis, Sriwijaya University.

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Abstract

Research on mapping annual and interannual rainfall patterns in Indonesia has not been widely conducted. One of the obstacles is the existence of quite large rainfall diversity that occurs in almost all regions of Indonesia. The diversity of rainfall patterns in Indonesia is due to the influence of atmospheric dynamics (air circulation) on a global and regional scale, ocean dynamics, local conditions, cloud and rain formation patterns such as topography and sea surface temperature in Indonesian waters. The dynamics of these parameters need to be studied because they play an important role in anticipating extreme climate change in Indonesia. Several previous researchers have proven the relationship between climate parameters and rainfall, but most previous researchers have only reviewed one parameter for rainfall. Based on the reference search that has been carried out, since 2003 there has been no data update regarding the mapping of annual and interannual rainfall patterns in Indonesia. The data recorded in the latest research that discusses rainfall mapping with rainfall data from 1961-1998, of course this data must be updated considering that recently the variation in rainfall has been quite significant in the Indonesian region so that hydrometeorological disasters cannot be controlled, such as the devastating floods and landslides on the island of Kalimantan in 2021. This study was designed to examine the mapping of annual and interannual rainfall patterns with hydrometeorological parameter data from Monthly Precipitation from Princeton University from January 1948 to December 2016 and monthly rainfall data Southeast Asian Climate Assessment & Dataset (SACA&D) from January 1981 to December 2016, Sea Surface Temperature (SST) from The Hadley Centre Global Sea Ice and Sea Surface Temperature (HADISST), Wind and Specific Humidity from the National Centers for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR), Monsoon Index from the Australian Bureau of Meteorology (BOM), Dipole Mode Index (DMI) from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Niño3.4 Index from the National Oceanic and Atmospheric Administration (NOAA) with time intervals from January 1948 to December 2016 and from January 1981 to December 2016. This study combines reanalysis data to produce a picture of the possibility of the influence of two dominant climate modes in the tropical Indo-Pacific region (i.e., IOD and ENSO). The influence of the Indian Ocean Dipole (IOD) centered in the Tropical Indian Ocean (TIO) and the El Niño-Southern Oscillation (ENSO) in the Tropical Pacific Ocean (TPO) on rainfall in Indonesia was evaluated using monthly rainfall data from the Southeast Asian Climate Assessment & Dataset (SACA&D) from January 1981 to December 2016. The rainfall data were analyzed using the EOF method which produced two main modes, namely PC1 and PC2 with variances of 35.23% and 13.07%, respectively. Simultaneous correlation between Reconstruction of Empirical Orthogonal Function (REOF) and climate indices at the end of the dry season in August-September-October (ASO) and the beginning of the rainy season in November-December-January (NDJ) revealed that the IOD and ENSO events have a significant strong negative correlation to the eigen values of EOF1 and EOF2. This indicates that the cooling (warming) of sea surface temperatures in local Indonesian waters during positive (negative) IOD and El Niño (La Niña) events can reduce (increase) rainfall. The anomalies of regional rainfall REOF1 and REOF2, SST and vertical velocity during El Niño, La Niña, positive/negative IOD years can be clearly depicted using the composite method. Wet conditions during negative IOD and La Niña events that occur simultaneously are much wetter than during a single La Niña event. The identification results are expected to contribute to the government in anticipating changes in rainfall pattern variability as a form of hydrometeorological disaster response in the Indonesian region. Rainfall variability with Monthly Precipitation data from Princeton University from January 1948 to December 2016 was investigated based on the analysis of the Empirical Orthogonal Function (EOF) method in the Indonesian region. The analysis begins by taking three main modes of EOF results, namely EOF1, EOF2 and EOF3. The EOF1 region is southern Indonesia from southern Sumatra to Timor Island, part of Kalimantan, part of Sulawesi, and part of Irian Jaya. The EOF2 region is located in northwest Indonesia and covers the northern part of Sumatra and the northwestern part of Kalimantan. The EOF3 region covers Maluku and part of Sulawesi (close to the western Pacific region). The monthly rainfall data used are Monthly Precipitation data from Princeton University from 1948 to 2016. The results of the analysis with this data reveal that the three rainfall regions show semi-annual, annual and several other important inter-annual periods. Researchers observed the influence of SST and vertical winds along the Indo-Pacific Ocean. The climate parameters analyzed include the Niño3.4 index, DMI and vertical velocity. The EOF1 region responds to the strongest SST, followed by the EOF3 region. In the EOF2 region, the ENSO/IOD-related signal is very weak compared to the other two regions. The EOF1 and EOF3 regions respond significantly positively to local SST and significantly negatively to ENSO/IOD during the peak of the dry season (ASO) and weaken during the rainy season (NDJ). The strong influence of ENSO allows these two regions to experience long droughts in years of El Niño and positive IOD events, due to its negative response. These results indicate that high (low) SST in the Niño3.4 Pacific Ocean region can reduce (increase) the amount of rainfall in the Indonesian region. The results of this study are expected to contribute to various scientific fields that are closely related to efforts to anticipate hydrometeorological disasters with the results in the form of accurate and scientific mapping of annual and inter-annual rainfall patterns in the Indonesian region. A comprehensive study, it is expected that the results obtained can describe annual and inter-annual rainfall patterns in the Indonesian region well and reliably. By knowing the mapping of rainfall patterns in the Indonesian region, it can be used as a reference for the government to create and formulate mitigation policies against global extreme climate change events and can provide preventive measures to anticipate hydrometeorological disasters in areas prone to disasters according to the mapping of rainfall patterns produced in this study.

Item Type:	Thesis (Doctoral)
Subjects:	Q Science > QC Physics > QC1-999 Physics Q Science > QC Physics > QC851-999 Meteorology. Climatology. Including the earth's atmosphere
Divisions:	08-Faculty of Mathematics and Natural Science > 44001-Mathematics and Natural Science (S3)
Depositing User:	Melly Ariska
Date Deposited:	16 Jan 2025 13:23
Last Modified:	16 Jan 2025 13:23
URI:	http://repository.unsri.ac.id/id/eprint/165052

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