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Propagation Characteristics of Madden Julian Oscillation in the Indonesian Maritime Continent: Case Studies for 2020-2022 Istiqomah, Fadhilatul; Yulihastin, Erma; Wiratmo, Joko; Hermawan, Eddy; Trilaksono, Nurjanna Joko; Irawan, Dasapta Erwin; Yohanes, Kristy Natasha; Ayunina, Amalia Qurrotu
Agromet Vol. 38 No. 1 (2024): JUNE 2024
Publisher : PERHIMPI (Indonesian Association of Agricultural Meteorology)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29244/j.agromet.38.1.1-12

Abstract

Madden-Julian Oscillation (MJO) can affect weather and climate variability in the Indonesian Maritime Continent. MJO propagation is not always the same, previous research has classified MJO into 4 categories: slow, fast, stand, and jump. The objective of this study is to investigate the differences in MJO propagation and the factors that impact it. Daily data for variables such as Outgoing Longwave Radiation (OLR), zonal wind, and sea surface temperature are utilized in this research. The collected data is processed using composite methods based on the 8 MJO phases, with a specific focus on the years 2020, 2021, and 2022. The research findings suggest that warm sea surface temperatures in the Pacific Ocean and zonal winds dominated by Kelvin waves are favorable for MJO propagation. Conversely, cooling sea surface temperatures in the Pacific Ocean and zonal winds dominated by equatorial Rossby waves can hinder MJO propagation. Future researchers are expected to examine the impact of MJO propagation during extreme rainfall occurrences in several regions of Indonesia, as well as the application of machine learning and deep learning methods to predict MJO propagation in the future.
Identification of Rossby Atmosphere-Tropical Cyclone in Eastern Indonesian Waters Suhendar, Maldiva Hafiza Anjarika; Yulihastin, Erma; Syalsabilla, Alya Fitri; Azzahra, Syifa Alifia; Handoyo, Gentur; Ridwan, Agus Wawan; Dawami, Maulana Dwi Nur
Jurnal ILMU DASAR Vol 25 No 2 (2024)
Publisher : Fakultas Matematika dan Ilmu Pengetahuan Alam Universitas Jember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.19184/jid.v25i2.43674

Abstract

Recent research has revealed that tropical cyclones can develop over eastern Indonesian waters influenced by marine heatwaves and Rossby waves in the atmosphere. However, there is no study documenting tropical cyclones that occur in conjunction with atmospheric Rossby waves (Rossby Atmospheric-Tropical Cyclones) and their association with increased sea surface temperatures in eastern Indonesian waters. This study aims to document the influence of Rossby waves in the atmosphere on the formation of tropical cyclones around the Indonesian region using 5 case studies in 2017-2022, namely: December 2017, January 2020, December 2020, December 2021, and April 2022. This study uses wind data, sea surface temperature, specific humidity, and temperature (2m) obtained from the European Re-Analysis (ERA5) with a temporal and spatial resolution of one hour and 0.25°×0.25°. The identification of Rossby waves is based on the Rossby index issued by the North Carolina Institute for Climate Studies (NCICS). In this study, the Rossby Atmosphere-Tropical Cyclone is grouped into three phases, namely: early phase, mature phase, and late phase, using composite and statistical methods to calculate anomalies. The results showed that in the early phase, the existence of Rossby waves was shown by two twin vortices over eastern Indonesia, which was supported by high specific humidity, warming sea surface temperature (>+0.4°C), and higher surface temperature (>+0.3°C) over Timor. In the mature phase, the twin vortices over eastern waters transformed into a tropical cyclone over the Philippines. In the final phase, specific humidity decreases, sea surface temperature cools (<-0.3°C), and surface temperature decreases (<-0.3°C). The results also prove the crucial role of Timor waters in forming Rossby waves that can grow into tropical cyclones around Indonesia.
Ocean Contribution to Coastal Heavy Rainfall During Dry Season (Case Study of Bengkulu 2016-2022) Firdaus, Muhamad Dadan; Syamsuddin, Mega Laksmini; Yulihastin, Erma
BERKALA SAINSTEK Vol 12 No 2 (2024)
Publisher : Universitas Jember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.19184/bst.v12i2.43989

Abstract

This study aims to determine the contribution of the ocean to the intensity of heavy rainfall in Bengkulu, Indonesia during the dry season (2016-2022). The primary data used in this study is daily rainfall data from the Bengkulu Meteorology Climatology and Geophysics Agency BMKG station. In addition, supporting data are also used in the form of rain parameters, 10 m wind, sea surface temperature, and sea surface currents from ERA5 reanalysis data with daily temporal and spatial resolution of 0.05°. The method used is a composite method that calculates 64 samples of heavy rain. The results showed that low-speed winds formed an eddy in the sea area west of Sumatra which together with heavy rains resulted in an increase in sea surface temperature. In addition, for the 2019 dry season case study, 1 m/s winds near the Bengkulu coast are associated with heavy rainfall (>100 mm) and during the 2022 dry season, 1-4 m/s winds spread from the coast to the Indian Ocean sea, causing rainfall (>50 mm) on the Bengkulu coast and surrounding areas. When sea surface temperatures are high there is the potential for heavy rainfall in areas of low wind speed. The current in each year is different and has a pattern, every year a strong current from the Indian Ocean will move towards the coastal area every 3-year period. When in 2016 the current (>1 m/sec) is in the Indian Ocean, then the following year 2017 the current (>1 m/sec) shifts closer to the coastal area until in 2018 a strong current is on the coast and the following years a stronger current comes from the Indian Ocean.
The Comparison of Reservoir Impoundment Duration between Ground Observation and Satellite Precipitation Product over Karian, Indonesia Adhi Priyambodho , Bambang; Tiffanyputri Kristiani, Anugerah; Kurniawan, Vittorio; Yulihastin, Erma; Nugraha Putra Herlambang , Rizky; Qodrita Avia , Lely; Satyawardhana , Haries; Wigati , Restu; Subekti , Subekti; Putu Purnaditya , Ngakan; Setyo Nugroho, Paulus
International Journal of Science and Environment (IJSE) Vol. 5 No. 1 (2025): February 2025
Publisher : CV. Inara

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.51601/ijse.v5i1.121

Abstract

The initial filling phase of reservoirs is a critical period that demands close supervision to ensure safety and functionality. During this phase, the dam is slowly filled with water, submerging floodplains until it reaches its intended storage capacity. This process assesses the response of the dam to water filling and its overall safety, with continuous monitoring and evaluation against design standards. The duration and rate of filling depend on several factors, i.e., precipitation, dam height, and hydropower plant sensitivity; thus, precipitation was the prominent driving force. However, as continuous precipitation data, multi-satellite global precipitation maps under the Global Precipitation Measurement near-real-time (GSMaP NRT) satellite products offer an alternative but tend to underestimate or overestimate rainfall values, posing challenges for accurate predictions. Bias correction methods of GSMaP NRT product in the spanning period of 2005–2022 demonstrated in agreement with ground observation data through the application of the artificial neural network (ANN) method to reduce the error bias to produce reliable results. This study highlights the importance of the impoundment period for reservoir sedimentation and overall dam safety. It emphasises the need for accurate precipitation data in reservoir management and recommends rigorous bias correction when using satellite data to substitute ground measurements.