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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.
Improving Short-Term Weather Forecasting using Support Vector Machine Method in North Barito Wulandari, Ayu Vista; Trilaksono, Nurjanna Joko; Ryan, Muhammad
Jurnal Meteorologi dan Geofisika Vol. 25 No. 2 (2024)
Publisher : Pusat Penelitian dan Pengembangan BMKG

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31172/jmg.v25i2.1096

Abstract

Flooding is a recurring issue in North Barito Regency due to the overflow of the Barito River. Weather forecasts in the region rely mainly on Numerical Weather Prediction (NWP) models, which often fail to capture local details due to their grid-based homogenization. To address this limitation, statistical techniques such as Model Output Statistics (MOS) can enhance NWP outputs by representing local conditions more accurately . MOS establishes statistical relationships between response variables (predictands) and predictor variables derived from NWP outputs, enabling operational applications without the need for advanced instruments. This study utilizes rainfall data from 2021-2022 from the Beringin Meteorological Station in North Barito as the response variable, while data from the Integrating Forecasting System (IFS) model serve as the predictor variables. The Support Vector Machine (SVM) method is employed to identify the relationship between predictor and response variables. By integrating the MOS technique with the SVM method, this research aims to improve the accuracy of weather forecasting, particularly for short-term predictions in North Barito. This approach demonstrates the potential to enhance localized weather predictions by addressing the limitations of conventional NWP models. The results indicate a consistent reduction in RMSE across all experiments conducted. Furthermore, the SVM model showed notable improvements in bias values and exhibited a stronger correlation compared to the original outputs from the IFS model. The percentage improvement (%IM) in rainfall forecasts, following correction using the SVM model, increased by 5.03%. The percentage improvement (%IM) in rainfall forecasts, following correction using the SVM model, increased by 5.03% for use as a predictor variable in the applied SVM method. In contrast, a combination of surface pressure, temperature across various layers, and rainfall proved to be the the most effective input variables for enhancing the accuracy of weather forecasting in North Barito using the SVM model.
Comparative Analysis of Diurnal and Seasonal Variations in Precipitation of Mesoscale Convective System and Non-Mesoscale Convective System over Borneo Island Azka, Mukhamad Adib; Trilaksono, Nurjanna Joko
Jurnal Meteorologi dan Geofisika Vol. 25 No. 2 (2024)
Publisher : Pusat Penelitian dan Pengembangan BMKG

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31172/jmg.v25i2.1101

Abstract

Convective storms, which play a critical role in producing severe weather events, are often associated with mesoscale convective systems (MCS). The most favorable tropical regions for MCS development include the Indonesian Maritime Continent (IMC), with Borneo Island being a prominent area. Borneo Island features unique topography and is influenced by the surrounding oceans, resulting in MCS with the largest average size and most extended lifespan compared to other islands within the IMC. Previous studies on MCS focused on occurrence statistics and case studies. However, analyses distinguishing characteristics of MCS and non-MCS precipitation remain limited over the IMC. This study examines the diurnal and seasonal variations and their respective contributions over Borneo Island. MCS identification and tracking were performed using the Flexible Object Tracker (FLEXTRKR) algorithm. The results indicate that MCS precipitation typically occurs from nighttime to early morning, while non-MCS precipitation primarily occurs during the daytime until the evening. Furthermore, MCS precipitation occurs more frequently over the ocean, while non-MCS precipitation is primarily observed over land. Seasonally, MCS precipitation is most prominent during the December–January–February (DJF) season, particularly over the South China Sea, parts of West Kalimantan, Sarawak, Central Kalimantan, and the Java Sea. Conversely, MCS precipitation is less dominant during the June–July–August (JJA) season. The contribution of precipitation produced by MCS exceeds 50% of the total precipitation, whereas non-MCS precipitation contributes approximately 20–40%. The differences in precipitation produced by MCS and non-MCS clouds will affect for soil water content, vulnerability to hydrometeorological disasters, and further understanding of climate and weather.
EVALUASI METODE KOREKSI BIAS UNTUK PREDIKSI CURAH HUJAN BULANAN ECMWF SEAS5 DI INDONESIA Hutauruk, Rheinhart C H; Rahmanto, Edi; Al Habib, Abdul Hamid; Yoku, Priskila Wilhelmina; Giriharta, I Wayan Gita; Trilaksono, Nurjanna Joko; Hadi, Tri Wahyu
Jurnal Meteorologi dan Geofisika Vol. 25 No. 2 (2024)
Publisher : Pusat Penelitian dan Pengembangan BMKG

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31172/jmg.v25i2.1124

Abstract

The seasonal rainfall forecast from ECMWF SEAS5 often suffers from biases that reduce its accuracy, limiting its use in applications like water resource management and agricultural planning. This study evaluates the effectiveness of bias correction methods in enhancing the skill of ECMWF SEAS5 seasonal precipitation forecasts in Indonesia. Observational data from 148 BMKG rain gauges and SEAS5 raw output from 2011 to 2020 are used. Three bias correction methods—linear scaling (LS), empirical distribution quantile mapping (EQM), and gamma distribution quantile mapping (GQM)—are applied to the raw model. Model performance is assessed using scatter plots, root mean square error (RMSE), correlation, and Taylor diagrams. The results show LS consistently outperforms EQM and GQM, reducing RMSE from 128 to 102 and improving correlation from 0.57 to 0.65. Additionally, Brier Score (BS) and Relative Operating Characteristic (ROC) analysis highlight significant improvements in probabilistic predictions, especially in areas with high rainfall variability. These findings indicate LS as a particularly effective approach for bias correction, enhancing accuracy and reliability. This study underscores the potential of applying bias correction methods like LS to improve ECMWF SEAS5 forecasts, supporting better decision-making for climate change adaptation and mitigation in Indonesia.
Dampak Aerosol Korosif pada Peralatan Distribusi Listrik PLN di Wilayah Pesisir Laut dan Implikasinya terhadap Keandalan Sistem Putra, Wildan Arya; Octavia, Farah Rizki; Hadi, Shamsul; Trilaksono, Nurjanna Joko; Abdillah, Muhammad Rais
JTERA (Jurnal Teknologi Rekayasa) Vol 10, No 1: Juni 2025
Publisher : Politeknik Sukabumi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31544/jtera.v10.i1.2025.99-104

Abstract

Korosi yang dipicu oleh paparan aerosol korosif di wilayah pesisir merupakan salah satu tantangan utama dalam menjaga keandalan sistem distribusi listrik. Penelitian ini bertujuan untuk mengidentifikasi dampak korosi terhadap peralatan distribusi listrik milik PLN, seperti konduktor A3C, bracket, dan suspension, yang mengalami kerusakan signifikan akibat kondisi lingkungan korosif di wilayah pesisir Pangandaran. Faktor-faktor seperti tingginya kadar garam di udara, kelembapan tinggi, dan paparan angin laut terbukti mempercepat laju korosi, yang berujung pada kerusakan infrastruktur distribusi serta gangguan pasokan listrik kepada ribuan pelanggan. Studi ini juga mengevaluasi langkah-langkah mitigasi yang dapat diterapkan, termasuk penggunaan material tahan korosi, aplikasi pelapisan protektif, serta pelaksanaan inspeksi dan pemeliharaan secara rutin. Hasil penelitian ini diharapkan menjadi dasar dalam perumusan strategi peningkatan keandalan distribusi listrik di kawasan pesisir.
Prekursor MJO-Crossing (MJO-C) dan MJO-Blocking (MJO-B) di Benua Maritim Berdasarkan Transpor Kelembapan Fahim, Akhmad; Trilaksono, Nurjanna Joko
Jurnal Meteorologi dan Geofisika Vol. 24 No. 2 (2023)
Publisher : Pusat Penelitian dan Pengembangan BMKG

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31172/jmg.v24i2.906

Abstract

Research on MJO propagation that is blocked when crossing the Maritime Continent (MC) is a complex problem. This research aims to determine the precursors of MJO-Crossing (MJO-C) and MJO-Blocking (MJO-B) based on moisture transport analysis. Hovmöller analysis on MJO-C and MJO-B is performed using precipitation data retrieved from the TRMM satellite (3B42v7) in the ONDJFM period 1998-2015 to characterize the propagation of MJO-C and MJO-B. The difference between MJO-C and MJO-B propagation is further investigated using specific humidity and horizontal wind data from ERA-Interim ECMWF to examine the moisture source and vertical structure of specific humidity in MJO-C and MJO-B. Additionally, we conducted wind divergence analysis at 700hPa to identify the characteristics of wind patterns in MJO-C and MJO-B events. Our investigation revealed that during the precursor period (day -15 to -5) or before MJO arrived at the Maritim Continent, there was a weakening of moisture supply in MJO-B events due to the existence of a westward-propagating dry anomaly. This dry anomaly mixed with the moist anomaly of MJO convection could reduce the intensity of moisture and dissipate MJO convection. The westward-propagating dry anomaly indicates the influence of Equatorial Rossby (ER) waves, which can inhibit MJO propagation across the Maritime Continent.
DAMPAK COLD SURGE (CS) TERHADAP NET SURFACE HEAT FLUX (NSHF) DI LAUT NATUNA Agdialta, Rezfiko; Ningsih, Nining Sari; Trilaksono, Nurjanna Joko
Jurnal Meteorologi dan Geofisika Vol. 25 No. 1 (2024)
Publisher : Pusat Penelitian dan Pengembangan BMKG

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31172/jmg.v25i1.1103

Abstract

Cold Surge (CS) events are often associated with rainfall occurrences in the Jakarta area. However, there is still limited literature on how CS affects other parameters in Indonesia. This study aims to contribute to this literature, particularly regarding the crucial role of CS in the interaction between the ocean and the atmosphere. This research uses the composite difference method to compare changes in Wind Speed (WS), Latent Heat Flux (LHF), Sensible Heat Flux (SHF), Shortwave Radiation (SWR), Longwave Radiation (LWR), and Net Surface Heat Flux (NSHF) during CS phases versus neutral conditions no CS (nCS). The composite difference results indicate an increase in wind speed in the study area, Natuna Sea, with values of 1.17 m/s, 1.45 m/s, and 1.69 m/s for December, January, and February, respectively. This finding explains that the increase in wind speed significantly influences LHF in the negative direction, meaning more LHF is transferred from the ocean to the atmosphere during the CS phase. LHF also predominantly affects NSHF in the study area during the CS period, indicating that more NSHF is leaving the ocean and entering the atmosphere compared to the amount entering the ocean from the atmosphere during the CS phase.
PERBANDINGAN METODE ASIMILASI DATA RADIANS SATELIT HIMAWARI-8 UNTUK PREDIKSI HUJAN DI KALIMANTAN TIMUR (STUDI KASUS HUJAN SANGAT LEBAT 2 – 4 JUNI 2019) Huda Abshor Mukhsinin; Trilaksono, Nurjanna Joko
Jurnal Meteorologi dan Geofisika Vol. 25 No. 2 (2024)
Publisher : Pusat Penelitian dan Pengembangan BMKG

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31172/jmg.v25i2.1097

Abstract

The performance of assimilating Himawari-8 satellite radiance data on a convection-permitting model (CPM) depends on the methods of assimilation. Hence, in this study, we compared the impact of different assimilation methods of Himawari-8 satellite radiance data on a CPM's prediction skills for the case of extreme rainfall in East Kalimantan, June 2nd – 4th, 2019. The study tested four schemes on the Weather Research and Forecasting (WRF) model at 3 km resolution, comparing a scheme without assimilation (NODA) and three schemes with different assimilation methods: 3DVAR, and Hybrid 3DEnVar (HYBRID, and DUALRES). Results showed that assimilation with hybrid 3DEnVar and 3DVAR techniques significantly improved the prediction skill of extreme rain, for instance, a 25% improvement of the true positive rate. The DUALRES scheme excelled in reducing biases in rainfall distribution. It was found that assimilation with the 3DEnVar method, particularly the DUALRES scheme, improved the prediction sensitivity to complex atmospheric dynamics, produced more accurate rainfall distribution and intensity, and improved the diurnal pattern of rainfall in East Kalimantan.
Identifikasi Aktivitas Konveksi Menggunakan Model WRF-ARW dan Indeks Stabilitas Atmosfer di Cekungan Bandung: Identifikasi Aktivitas Konveksi Menggunakan Model WRF-ARW dan Indeks Stabilitas Atmosfer di Cekungan Bandung Al Habib, Abdul Hamid; Hutauruk, Reinhart C. H.; Trilaksono, Nurjanna Joko; Wicaksana, Haryas Subyantara; Choir, Arini Amalia
Jurnal Meteorologi dan Geofisika Vol. 26 No. 1 (2025)
Publisher : Pusat Penelitian dan Pengembangan BMKG

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31172/jmg.v26i1.1126

Abstract

The Bandung Basin, characterized by complex topography, experiences some of the highest occurrences of heavy rainfall and hail in Indonesia. This study focuses on forecasting convective activity associated with a thunderstorm and heavy rainfall event that triggered flooding in the Pagarsih area, West Java, on 4 October 2022. The spatiotemporal forecast characteristics of convection are assessed using atmospheric stability indices (CAPE, K Index, Total Totals Index, and Lifted Index), together with low-level convergence and updraft fields from the WRF-ARW model, to identify the development of convective cells influenced by the Bandung Basin’s topography. The results reveal a distinct spatiotemporal evolution of convection across mountainous and valley regions. In the early phase, convection first emerged over mountainous areas, driven by a gradual increase in atmospheric instability and low-level convergence, before developing over the valley. The forecasted stability indices show a rising trend 2–5 hours before the onset of thunderstorms and heavy rainfall in the Pagarsih area. At the mature stage, mountain convection was mainly initiated by solar radiation heating, while valley convection was predominantly triggered by mechanical forcing, characterized by a sudden surge in low-level convergence, instability indices, and updraft, leading to more explosive convective development. During dissipation, convection weakened in both regions; however, mountainous areas exhibited stronger convective recovery, indicating higher sensitivity to surface reheating.