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1	Atmospheric Sciences	ABS-9
Validation of CAMS Particulate Matter 2.5 (PM2.5) Products over Indonesia Aberta Rulinri Siahaan*, Aulia Nisa^ul Khoir, Ardhasena Sopaheluawakan, Alberth Christian Nahas, Budi Setiawan, Taryono, Hanifah Nurhayati, Mizani Ahmad, Sunaryo, Muhammad Fathi Robbani Centre for Applied Climate Services, Indonesia Agency for Meteorology, Climatology, Geophysics Abstract High quality monitoring of particulate matter 2.5 (PM2.5) data observations that covers entire Indonesia are crucial for air pollution management. Aside from its negative effects on health, its relationship with climate change also needs to be concerned. PM2.5 data from Copernicus Atmosphere Monitoring Service (CAMS) has been broadly used to complement the ground-based observation of PM2.5. This study aims to assess the validation of the CAMS based on the available ground-based measurement of the air quality indicator, PM2.5, over the Indonesia region. The validation includes 27 ground-based measurements of PM2.5 over Indonesia during the very recent years, 2021 - 2022. This study pursued the validation of the PM2.5 of CAMS products using the model statistical performance, including Mean fractional bias (MFB) and mean fractional error (MFE). The results of the temporal pattern of the PM2.5 of ground-based measurement and CAMS have varied variations. However, the results show that 89% from all the study locations have met the model performance goal. Additionally, all the study locations also have met the model performance criteria. Finally, this study proved a good performance of PM2.5 of CAMS products over Indonesia region. Keywords: CAMS, PM2.5, Indonesia Share Link | Plain Format | Corresponding Author (Aberta Siahaan)

2	Atmospheric Sciences	ABS-10
Influences of geomorphological and surface aerodynamic factors on the relationship between maximum and average wind speed in Indonesia Kidung Kinanti (1) and M. Rais Abdillah (2) 1) Undergraduate Program of Meteorology, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, Bandung, Indonesia 2) Atmospheric Science Research Group, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, Bandung, Indonesia Abstract The relationship between maximum wind speed and average wind speed is not linear and might be influenced by many factors. Past studies showed that the relationship can be affected by several geomorphology and surface aerodynamic factors. This study aims to reveal whether the geomorphology and surface aerodynamics factors have significant influences on the relationship between maximum and average wind speed in Indonesia. Daily maximum and average wind speed data over 2016-2022 from 56 Automatic Weather Stations (AWS) were utilized to obtain combined distribution patterns. The combined distribution patterns were clustered using the K-Means method to categorize stations with similar patterns. Six clusters of distribution patterns were found, showing some differences and similarities in geomorphological and surface aerodynamics factors. Most of geomorphological characteristics showed slight differences between the clusters, indicating that these factors might not have significant effect on the variation of the relationships between maximum and average wind. The surface aerodynamics factors This study finds that each cluster of stations has distinct geomorphological and surface aerodynamics characteristics, but currently we find no consistent pattern of parameters correlating with the relationship between maximum and average wind speed. To obtain more local and representative surface conditions, future studies may revisit the linkages using higher resolution of geomorphological and surface aerodynamics datasets. Keywords: Maximum wind speed, Average wind speed, Combined distribution, Geomorphological, Surface aerodynamics Share Link | Plain Format | Corresponding Author (Kidung Kinanti)

3	Atmospheric Sciences	ABS-11
Turbulence flux condition in Jakarta during Cross Equatorial Northerly Surge (CENS) Ahlil Ilmar Batuparan (1), I Dewa Gede A. Junnaedhi (1,2), M. Rais Abdillah (1,2), and Atsushi Inagaki (3) a) Faculty of Earth Sciences and Technology, , Bandung Institute of Technology, Bandung, Indonesia b) Department of Transdisciplinary Science and Engineering, Tokyo Institute of Technology, Tokyo, Japan Abstract Cross Equatorial Northerly Surge (CENS) causes the strengthening of monsoon winds from the north around the Karimata Strait and Java Sea. CENS was often associated with heavy rain in western Java, especially during the early morning. As a mesoscale process, CENS might influence microscale meteorological conditions such as turbulence fluxes. The micrometeorological observation campaign in two locations in Jakarta, namely KKP and LLH, gives the opportunity to study the effect of CENS on micrometeorological conditions. This study aims to examine how CENS change the micro-scale turbulence fluxes during wet season in Jakarta, Indonesia. This study focused on wet seasons, between December and January, during the period of 2017 to 2022. The CENS period is defined using ERA5 surface wind data over 105 E to 115 E and 5 S. The turbulence fluxes were estimated using eddy covariance method (EC) from the micrometeorological observation data at KKP and LLH. The mean meteorological and turbulent fluxes condition then compared between CENS and non CENS period. Although CENS causes stronger northerly winds, it does not have a significant influence on the turbulent momentum flux (Fm) in Jakarta. The turbulent sensible heat flux (QH) however, shows lower value during daytime, suggesting that CENS might suppress sensible heat transfer. The latent heat flux (QL) estimation at LLH also shows lower values during daytime under CENS occurrences. However, during early morning on CENS periods, the latent heat flux shows higher values. This result indicates that overland turbulence processes might induce early morning heavy rain that was observed during CENS period. Keywords: CENS, Turbulent Flux, Jakarta, Micro-scale, Meso-scale Share Link | Plain Format | Corresponding Author (AHLIL BATUPARAN)

4	Atmospheric Sciences	ABS-22
METEOROLOGICAL FACTORS AFFECTING DIURNAL VARIATIONS OF SOIL MOISTURE (CASE STUDY: PANCAWATI CARINGIN DISTRICT, BOGOR) Geraldin Andira Cahyarani Putri (a*), Dr. Rusmawan Suwarman, S.Si., M.T. (b), Teuku Reza, M.T. (c) Meteorology, Bandung Institut of Technology Jalan Ganesha 10, Bandung 40132, Indonesia *12820032[at]mahasiswa.itb.ac.id Abstract Soil moisture is influenced by meteorological factors, such as rainfall, air temperature, relative humidity, and solar radiation, each of which has an influence on different soil depths. This research examines the characteristics of soil moisture at various depths and its controlling factors based on available data in the mountains of Bogor. This research method is based on correlation analysis and diurnal variation of controlling factors (rainfall, solar radiation, relative humidity, and air temperature) and their correlation at soil depths of 25 cm, 50 cm, 75 cm, and 100 cm. The analysis results show that soil moisture fluctuations are influenced by air temperature, solar radiation, rainfall and relative humidity. The controlling factor that most influences diurnal variations at depths of 25 cm, 50 cm, 75 cm and 100 cm, namely variables at the same two hours times in the top layer. Lag correlation analysis shows that controlling factors directly influence soil moisture at all depths. Keywords: soil moisture, meteorological factors, diurnal variation Share Link | Plain Format | Corresponding Author (Geraldin Andira Cahyarani Putri)

5	Atmospheric Sciences	ABS-23
ASSESSING THE ROLE OF BASEFLOW IN WATERSHED DISCHARGE UNDER SEMI-ANNUAL RAINFALL: A CASE STUDY OF THE CIKAPUNDUNG SUB-WATERSHED Alecio Yusran Rizqullah (a), Edi Riawan (b), Fadhillah Nurzaki Waliyatullah (c), Fattah Ghiffari (c), Faza Haniyah Firstrizanda (c), Safinka Putri Minanda (a) a) Meteorology Departement, Faculty of Earth Science and Technology, Institut Teknologi Bandung, 40132, Indonesia b) Atmospheric Science Research Group, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, 40132, Indonesia c) Groundwater Engineering Departement, Faculty of Earth Science and Technology, Institut Teknologi Bandung, 40132, Indonesia Abstract Cikapundung River is one of tributaries of the Citarum River, serves as a vital water source for residents in the Bandung Basin while also contributing to frequent flooding in the southern Bandung region. This study aims to identify the hydrometeorological characteristics of the Cikapundung Sub-watershed, focusing on baseflow and discharge responses to rainfall, which is suspected to follow a semi-annual pattern. Using rainfall, runoff, elevation, land use, and soil type data, the GSSHA model was employed to simulate soil moisture scenarios and represent baseflow. The model was calibrated by comparing simulated and observed runoff, adjusting surface roughness and infiltration parameters until a match was achieved. Results show that the annual runoff pattern resemble the rainfall pattern, but the peak runoff lags by a month, likely due to rainfall infiltration in the upstream areas during the first peak, causing increased runoff downstream during the second peak. GSSHA modeling also highlights the critical role of soil moisture in influencing discharge, particularly during extreme events Keywords: Runoff, infiltration, Soil Moisture Share Link | Plain Format | Corresponding Author (Alecio Yusran Rizqullah)

6	Atmospheric Sciences	ABS-24
Impact of global climate change and urbanization on megacities Do Ngoc Khanh (a, b*), Alvin C. G. Varquez (b), Manabu Kanda (b) a) SIT Research Laboratories, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo, Japan 135-8548 b) Department of Transdisciplinary Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, Japan 152-8550 Abstract Global climate change and urbanization-induced warming (urban heat island effect) are the two main drivers of warming in cities. In the projection of future climate, coarse-resolution global climate models are not suitable for looking into the heterogeneous urban surface and their changes. On the other hand, regional climate models, which are capable of looking into cities in detail, have never been used to investigate the global urban climate. Here we show that urbanization significantly increases exposure to extreme warming for megacity residents. We reflect urbanization between the 2010s and the 2050s into our model by considering the spatiotemporal change in urban surface (buildings and anthropogenic heat emissions) induced by urban population and economic growth. We found that in the 2050s, under the worst-case scenario, 78 percent of megacity residents will be exposed to 2.5 K warming, much higher than the projection of 65 percent when urban warming is left out. Our results highlight the importance of accounting for local urbanization in future global urban climate projection. We also introduce the modeling framework used in this study. The framework is applicable for all cities worldwide and was incorporated into the Weather Research and Forecasting (WRF) model v4.6. Keywords: global climate change, urban climate, WRF modeling, anthropogenic heat Share Link | Plain Format | Corresponding Author (Do Ngoc Khanh)

7	Atmospheric Sciences	ABS-25
Sea-Breeze Front Propagation over The Northern Coast of West Java and Association with Inland Convections in The Dry Season Banu W. Yonas (a*,b), Tri W. Hadi (a) a) Faculty of Earth Science and Technology, Bandung Institute of Technology b) Meteorology, Climatology, and Geophysical Agency, Indonesia Jalan Ganesha 10, Bandung 40132, Indonesia *banuyonas[at]gmail.com Abstract Sea-breeze circulation is known to well develop during the dry season months of July to September over the northern coast of West Java. On the other hand, compared to other areas in Java Island, strong convection and heavy rainfall more frequently occur in the most western part of the Island during the dry season. This study investigates the relationships between sea-breeze development and propagation, and the convections around this region. By analyzing surface winds and relative humidity observed over two sites near Jakarta, sea-breeze intrusion times and the speed of sea-breeze front propagation can be estimated. It is found that on average, sea-breeze develops around 09:00 LT and propagates at a speed of about 1.44 m/s near over the coastal plain. However, there is also variation in the sea-breeze propagation speed ranging from 0.49 m/s to 4.69 m/s. Meanwhile, convective activites are identified from satellite imageries. Further analyses reveal that faster sea-breeze propagation tend to be associated with deeper and larger convections, compared to the slower ones. This indicates that sea-breeze propagates faster under more unstable atmosphere, consistent with previous studies. Impacts of collisions of sea-breezes developed over different coastlines have not been thoroughly analyzed in this study. Keywords: Sea-breeze- Propagation- Convections Share Link | Plain Format | Corresponding Author (Banu Wijaya Yonas)

8	Atmospheric Sciences	ABS-31
Development of wind hazard map in Indonesia Muhammad Rais Abdillah, Hartono Wijaya, Prasanti Widyasih Sarli Institut Teknologi Bandung Abstract One of the most recurring disasters in Indonesia is wind-related disaster. However, information about extreme wind is quite sparse and rarely available from conventional weather stations. In the recent decade, the growing number of automatic weather stations (AWS) has provided opportunities to investigate more extreme wind events. By combining a total of 201 AWS data and a long-term simulated extreme wind speed from ERA5 global atmospheric reanalysis, this study develops a wind hazard map for Indonesia. A quantile mapping method is used to calibrate the wind distributions from reanalysis to AWS. The wind speed maps at return periods of 2, 5, 10, 20, 50, 100, 200, 500, and 1000 years are calculated from fitting the calibrated ERA5 annual maxima of wind into the Gumbel distribution. The resulting wind map shows extreme wind spatial characteristics where the wind is stronger over southern and southeastern Indonesia, and over mountainous regions of Sumatra and Celebes. The wind speed ranges from between less than 10 to 25 m/s at 2-year return period, to between 15 to greater than 40 m/s at 1000-year return period. The production of these wind maps hopefully can help in studies about wind-disaster risks and in structural planning for building construction. Keywords: disaster, extreme wind, hazard analysis Share Link | Plain Format | Corresponding Author (Muhammad Rais Abdillah)

9	Atmospheric Sciences	ABS-33
Regional-scale of Climate Change over Borneo Based on Conformal Cubic Atmospheric Model Fattah Ghiffari (a*), Erma Yulihastin (b), Haries Satyawardhana (b), Lely Qodrita Avia (b) , Risyanto (b), Parwati Sofan (c), Robi Muharsyah (d), Ahmad Yani (e), Edi Riawan (f) (a) Groundwater Engineering Department, Faculty of Earth Science and Technology, Institut Teknologi Bandung, 40132, Indonesia (b) Research Center for Climate and Atmosphere, National Research and Innovation Agency, Bandung, 40135, Indonesia (c) Research Center for Oceanography, National Research and Innovation Agency, Bogor, 16911, Indonesia (d) Indonesian Agency for Meteorology, Climatology, and Geophysics, Jakarta, 10720, Indonesia (e) Tanjungpura University, Pontianak, West Kalimantan, 78124, Indonesia (f) Atmospheric Science Research Group, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, 40132, Indonesia Abstract The model simulations for Borneo suggest potential difficulties in capturing the variability of rainfall on regional scales due to complex topography and climate interactions. This study utilizes a high-resolution Conformal Cubic Atmospheric Model (CCAM) to address the impacts of climate change on a regional scale over Borneo by analyzing key parameters such as precipitation, surface temperature, mean sea level pressure, and relative humidity over Borneo for the near future (2023 - 2033). The study employs dynamical downscaling using the Conformal Cubic Atmospheric Model (CCAM) to refine the spatial resolution of Global Climate Model (GCM) data from 60 km to 14 km, allowing more detailed regional climate analysis over Borneo. An anomaly method was also applied to quantify the deviations in precipitation, surface temperature, mean sea level pressure (MSLP), and relative humidity from baseline climatological values during the projection period. We also found that the MAM (March-April-May) and SON (September-October-November) seasons show higher rainfall than the DJF (December-January-February) seasons. Meanwhile, relative humidity tends to decrease in the future compared to previous years. Mean sea level pressure (MSLP) tends to increase over the border of Indonesia and Malaysia in the JJA (June-July-August) season but decreases over southern Borneo in the MAM (March-April-May) and SON (September-October-November) seasons. There is a noticeable increase in temperature from the MAM (March-April-May) to SON (September-October-November) season in the east south region. However, further research is required to validate these projections. Keywords: Climate Change, Regional Scale, Conformal Cubic Atmospheric Model (CCAM) Share Link | Plain Format | Corresponding Author (Fattah Ghiffari)

10	Atmospheric Sciences	ABS-46
ENHANCING HAIL PREDICTION ACCURACY THROUGH RADAR DATA ASSIMILATION IN ASSOCIATION WITH LARGE-SCALE WEATHER PATTERNS: A CASE STUDY OF SURABAYA, FEBRUARY 21, 2022 Nurjanna Joko Trilaksono (a), Muhaji Sahnita Putri (b) (a) Atmospheric Science Research Group, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung, Indonesia (b) Master Program in Earth Science, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung, Indonesia Abstract Hail is one of the extreme weather phenomena that often occurs in Indonesia and has increased in frequency in recent years. Hailstorms can cause widespread damage to crops, property, infrastructure, and can even pose risks to human safety, with larger hailstones presenting a particularly severe threat. Predicting hail events remains a significant challenge, especially due to limitations in observations and detection methods. However, efforts to improve weather prediction continue, including combining observational data with previous short-term forecasts. Improving models by assimilating radar reflectivity and radial velocity data can enhance the initial conditions of moisture and wind speed, potentially affecting the formation of convective clouds leading to rainfall. This study utilizes the Weather Research and Forecasting Data Assimilation (WRFDA) model with the 3DVar method. The assimilated data include reflectivity and radial velocity data from the BMKG^s C-Band Weather Radar. Hail in Surabaya is influenced by Large-Scale Weather (LSW) patterns. The results of this study demonstrate that radar data assimilation performs better than without assimilation. Model performance was evaluated using the Fraction Skill Score (FSS) and bias methods. The best FSS result was 0.7 when radar reflectivity data assimilation was applied, while the worst result was 0.38 without assimilation. The best bias value was 0.5 with assimilation, compared to 0.2 without assimilation. The evolution of radar reflectivity values between observations and experiments showed consistency in terms of intensity, timing, and area of hail occurrence when radar data assimilation was applied. The distribution of the Maximum Estimated Size of Hail (MESH) values showed better spatial accuracy of the hail area when using radar data assimilation compared to without assimilation. Specifically, the radar data assimilation experiment for hail in Surabaya was able to estimate MESH reaching 10 mm, with observed MESH values being >10 mm. Hail events associated with LSW can enhance predictive accuracy, particularly within operational forecasting. Keywords: Hail, Weather Radar, Data Assimilation, Weather Research Forecasting Data Assimilation (WRFDA) Share Link | Plain Format | Corresponding Author (Muhaji Sahnita Putri)

11	Atmospheric Sciences	ABS-56
Anomalously Wet Dry Seasons in Indonesia and Moisture Convergence Anomalies during The Cool Phase of Different ENSO Types Gammamerdianti and Tri Wahyu Hadi Institut Teknologi Bandung Abstract Dry season in Indonesia typically occurs from June to September, overlapping with the Indian Summer Monsoon (ISM) period, during which India sub-continent and its surroundings receive large amount of moisture transported from oceans in the Indo-Pacific region. However, there have been years with anomalously wet dry season, more commonly known as ^wet dry-season^ (WDS) among the media, in Indonesia. On the other hand, the Meteorology, Climatology, and Geophysical Agency of Indonesia (BMKG) officially defines seasonal rainfall variations by three categories i.e., above normal (AN), normal (N), below normal (BN). However, there is no clear definition of WDS referring to AN criteria of the dry-season rainfall. This study attempts to make clear definition of WDS by applying the criteria of AN, N, and BN the seasonal rainfall variations on gridded rainfall data. Moisture convergence anomalies associated with identified years of wet-dry season are also analyzed. The results show that, during the period of 1993 to 2022, WDS is identified in eight years i.e., 1995, 1996, 1998, 2010, 2013, 2016, 2021 and 2022. General cool-phase ENSO (La Nina) year (such that defined using NINO 3.4 index) identification only explains 40% of the WDS events. When definitions of Eastern- and Central-Pacific (including mixed type) are used, 80% of the events can be associated with La Nina. These WDS events are characterized by distinct dipole moisture convergence patterns, especially over Indonesia and South Asia. Moisture convergence indices developed over those regions show anomalous evolution that might indicate a precursor to WDS events. More studies are needed to understand cases of WDS that cannot be directly associated with La Nina. Keywords: Rainfall in dry season, anomalous wet-dry season identification, ENSO, moisture transport convergence Share Link | Plain Format | Corresponding Author (Gammamerdianti Gammamerdianti)

12	Atmospheric Sciences	ABS-58
Variation of Asia-Australia Monsoon to Mesoscale Convective System on East Java Prasetyo Umar Firdianto (a*), Bagus Satrio Wicaksono (b), Adi Mulsandi (c), Achmad Zakir (d), Bangun Muljo Sukojo (e) a) b) e) Department of Geomatics Engineering, Sepuluh Nopember Institute of Technology Kampus ITS Sukolilo, Surabaya 60111, Indonesia *prasetyo.firdianto[at]bmkg.go.id c) d) Department of Meteorology, Indonesian College of Meteorology Climatology and Geophysics Jalan Perhubungan I No.5, Tangerang Selatan 15221, Indonesia Abstract Indonesia maritime continent with strong convection activities triggers the formation of clouds that can develop and evolution into systems on larger scale in the form of Mesoscale Convective System (MCSs). It can trigger extreme weather that effect to hidrometeorological disasters, such as extreme rain, heavy thunderstorm, and gale wind. The Asian-Australian monsoon has an important influence in determining activities of MCSs in the East Java. The data are weather satellite of Himawari, zonal wind and meridional wind ECMWF 850 mb. Determination of the MCSs follows the physical characteristics in the Maddox algorithm and the AUSMI index follows the Kajikawa algorithm. The method used is quantitative analysis of coefficient of correlation and determination, and qualitative in the form of descriptive analytic. It can be know that the Asian-Australian monsoon have low influence on the MCSs in the East Java. AUSMI index has the same pattern and phase with frequency of MCSs on a monthly or seasonal (period 2014-2018). However, time of maximum and minimum frequencies event tends to be faster than the event of Asian and Australian monsoons. The frequency of 25-250 km is more dominant than 250-2500 km and the foremost life duration is 1-3 hours. The spatial distribution of 25-250 km is more evenly distributed than MCSs 250-2500 which only occur at certain times and point. The area that has a strong intensity of the occurrence of the most dominant MCSs is Southeastern Java. Keywords: MCSs- Monsoon- AUSMI Share Link | Plain Format | Corresponding Author (Prasetyo Umar Firdianto)

13	Atmospheric Sciences	ABS-64
IDENTIFICATION OF URBAN BIAS IN TEMPERATURE TRENDS ON JAVA ISLAND 1963-2022 Qonita Fathan Mubina (1), Muhammad Ridho Syahputra (1,2), Rusmawan Suwarman (1,2) 1. Undergraduate Program of Meteorology, Faculty of Earth Science and Technology, Institut Teknologi Bandung, Bandung, Indonesia 2. Atmospheric Science Research Group, Faculty of Earth Science and Technology, Institut Teknologi Bandung, Bandung, Indonesia Abstract Temperature change is a key indicator of climate change. However, with increasing urbanization, there is a factor of uncertainty in the calculation of temperature trends, especially in urban areas. With this uncertainty, it is necessary to learn more about urban bias in Indonesia, especially in Java Island which has the highest level of urbanization in Indonesia. This study aims to identify urban bias in temperature trends on Java Island in the last two climate periods (1962-1992 and 1993-2022) and identify spatial variations of urban bias in temperature trends on Java Island. The data used in this study are observational data of surface temperature, nighttime brightness, population density and ERA5 (The European Centre for Medium-Range Weather Forecast (ECMWF) Reanalysis 5-th Generation) reanalysis surface temperature. Urban and rural classifications are calculated based on population density and nighttime brightness which are then derived into the degree of urbanization. Calculation of temperature trends using linear regression and calculation of urban bias with the urban minus rural method. In the identification of urban bias with observational data, positive urban bias is identified in the trend of maximum, average and diurnal range temperature anomalies. In the identification of urban bias with reanalysis data in the first period (1963-1992) there is only a positive urban bias in the minimum temperature anomaly trend, while in the second period (1993-2022) the majority of urban bias is positive with urban bias in the average temperature anomaly trend of 16%. In terms of spatial variation, the West Java region has the highest urban bias. Keywords: Temperature, Urban bias, Urban, Rural, Java Island Share Link | Plain Format | Corresponding Author (Qonita Fathan Mubina)

14	Atmospheric Sciences	ABS-65
EVALUATION OF THE CLIMATE FORECAST SYSTEM (CFS) MODEL IN PREDICTING THE MADDEN JULIAN OSCILLATION (MJO) DURING BOREAL WINTER Friska Chania(1), Muhammad Ridho Syahputra(1,2), Nurjanna Joko Trilaksono(1,2) 1. Undergraduate Program of Meteorology, Faculty of Earth Science and Technology, Institut Teknologi Bandung, Bandung, Indonesia&#8239- 2. Atmospheric Science Research Group, Faculty of Earth Science and Technology, Institut Teknologi Bandung, Bandung, Indonesia&#8239-&#8239- Abstract The Madden Julian Oscillation (MJO) has garnered the attention of scientific practitioners as it represents a source of predictability for subseasonal to seasonal (S2S) forecasts, bridging the gap between weather and seasonal predictions. One S2S model with potential for predicting sub-seasonal conditions in Indonesia is the Climate Forecast System (CFSv2). Currently, MJO index predictions are presented in the form of MJO phase diagrams- however, limitations in predicting the MJO index may constrain the analysis of existing models. Therefore, this study aims to evaluate the performance of the CFSv2 model in predicting the MJO index using the ^mjoindices^ tools developed by Hoffman. The calculation of the MJO index is performed using the ^mjoindices^ tools from reanalysis data and operational CFSv2 model data for the boreal winter period (November, December, and January) from 2011 to 2021. Model performance evaluation is conducted deterministically with metrics such as RMSE and CC, and probabilistically with CRPS for evaluating the probabilistic distribution of weekly MJO index averages, and Brier score for evaluating weekly MJO active events. The criteria for an active MJO event are an MJO index greater than 1 for five consecutive days. This study demonstrates that the ^mjoindices^ tools successfully calculated the OMI index and established an MJO index prediction system utilizing the ensemble prediction system of CFSv2 to forecast the phase and magnitude of the MJO index for the next 4 weeks. Although the performance evaluation of the CFSv2 model using RMSE and CC metrics did not show significant relationships between predictions and observations, probabilistic metrics such as CRPS and Brier score provide a more comprehensive picture. CRPS indicates that the model is more accurate in short-term predictions with the best value of 0.368 at lead 1, though accuracy decreases as lead time increases. The Brier score at lead 1 is 0.352, indicating lower accuracy for weekly predictions. However, the model^s predictability does not experience significant accuracy decline across subsequent leads. Keywords: Madden Julian Oscillation (MJO), Model performance, CFSv2. Share Link | Plain Format | Corresponding Author (Friska Chania)

15	Atmospheric Sciences	ABS-80
Anomalies and Changes in Mass Meridional Circulation during a Positive Trend of Mass Term in the Atmospheric Angular Momentum Budget 1970-2020. Wirid Birastri, Tri Wahyu Hadi, Nining Sari Ningsih Doctoral Program of Earth Sciences, Faculty of Earth Sciences and Technology, Bandung Institute of Technology/Atmospheric and Earth System Sciences Research Group, Faculty of Science, Institut Teknologi Sumatera Atmospheric Science Research Group, Faculty of Earth Sciences and Technology, Bandung Institute of Technology Oceanography Research Group, Faculty of Earth Sciences and Technology, Bandung Institute of Technology Abstract In this research, mass flux and meridional budget analyses were conducted during the positive trend of the mass part of the Atmospheric Angular Momentum (AAM) Budget 1970-2020 using the ERA5 dataset. It is shown that after the 1970s, the equatorial belt experienced an increase in mass flux (I), primarily due to the addition of dry air (D) and water vapor flux (Q) from the Southern Hemisphere. The analysis of meridional wind and mass flux anomalies shows an increase in equatorward transport due to the strengthening of the SH-EQ circulation, which coincides with the weakening of the NH-EQ circulation. The latter contributes to a decrease in the amount of air mass that is transported leaving the equator. Furthermore, the annual climatology of mean mass meridional circulation calculated using the conventional Eulerian mean method over the 1970-1979 baseline period provides an overview of the meridional atmospheric circulation which is dominated by the Hadley Cell (HC) around the equator to 30 degree and the Ferrel Cell (FC) around 30 to 60 degree latitude in the NH and SH. The meridional cell intensity analysis reveals that after the 1970s, HC and HC in SH are strengthening, whereas weakening predominates in the NH. Hereafter, the Mass-Weighted Isentropic Zonal Mean (MIM) analysis was performed to examine for seasonality discrepancies in the patterns and interaction between tropical and extratropical circulation using residual zonal mean stream function. The strengthening of the SH HC and FC was persistent throughout the year. In contrast, in the NH, weaker circulation was observed throughout the season except for DJF. During this season, the extratropical direct (ETD) feature was observed, connecting the descending branch of the HC with the extratropical circulation in the NH. Meanwhile, the strengthening of SH-HC escalates to the 20N connecting the NH and extratropical SH circulation. Keywords: atmospheric angular momentum, mass term, trend, water vapor, dry atmosphere, mean meridional circulation Share Link | Plain Format | Corresponding Author (Wirid Birastri)

16	Atmospheric Sciences	ABS-82
Preliminary Results from Micrometeorological Observation in Sub-Urban Area of Tangerang, Indonesia Ahmad Fadlan(1), I Dewa Gede A. Junnaedhi(2*), M. Rais Abdillah(2), Nurjanna Joko Trilaksono(2), Atsushi Inagaki(3), and Manabu Kanda(3) 1) Study Program of Meteorology, State College of Meteorology, Climatology and Geophysics (STMKG), Tangerang, Indonesia 2) Atmospheric Science Research Group, Faculty of Earth Sciences and Teknology, Institut Teknologi Bandung, Bandung, Indonesia *dewa108[at]itb.ac.id 3) Department of Transdisciplinary Science and Engineering, Tokyo Institute of Technology, Tokyo, Japan Abstract In this paper, we are reporting the preliminary results of micrometeorological observation at sub-urban area of Tangerang, Banten, Indonesia. Tangerang is the buffer zone of the Jakarta megacity, hence rapidly developed in the past few years, following Jakarta^s rapid urbanization. Continues observation of micrometeorological conditions is necessary to track the impact of the progressive landscape change over the sub-urban area. The observation conducted at the rooftop of STMKG building at Tangerang is aimed to monitor the representative micrometeorological conditions in sub-urban area of Tangerang.The observation instruments consist of an ultrasonic anemometer, global radiation sensor, downward longwave radiation sensor, and an ambient temperature-humidity sensor. The total height of the anemometer is approximately 43 m above ground. All sensors were logged at a fast speed of 10 Hz and the data is collected manually for 8 days period, from 20 March until 28 March 2024. The mean values of each parameter were calculated every 30 minutes, and the turbulent fluxes were estimated using eddy covariance (EC) method.The results show that the prevailing wind at the site is influenced by sea and land breeze circulation. The site also has a relatively low drag coefficient from all directions, except for the northeast sector. The heat flux estimation shows an agreement with the observed radiation change. The turbulence statistic shows that the site is quite representative for micrometeorological monitoring for the sub-urban area of Tangerang. The observation will be continued, and the results will be used to study the dynamic of micrometeorological conditions in Tangerang. Keywords: turbulent flux, micrometeorology, sub-urban, Tangerang Share Link | Plain Format | Corresponding Author (Ahmad Fadlan)

17	Atmospheric Sciences	ABS-85
SPATIAL ANALYSIS OF METEOROLOGICAL DROUGHT IN SOUTH EAST ASIA AND AUSTRALIA REGION Imam Maulana Yosa(a*), Rusmawan Suwarman(b), Muhammad Ridho Syahputra(b) Meteorology, Bandung Institute of Technology Jalan Ganesha 10, Bandung 40132, Indonesia Abstract Southeast Asia and Australia have historically suffered significant losses due to droughts. Understanding these droughts can serve as a foundation for mitigation strategies aimed at reducing the damages they cause. Meteorological drought indices, such as the Standardized Precipitation Index (SPI), offer a valuable method for quantifying drought severity and frequency. This study employs monthly precipitation data from GPM_3IMERGM (0.1 degree x 0.1 degree) spanning 2000-2021 to calculate SPI for Southeast Asia and Australia across different time scales: 3 months (SPI-3), 6 months (SPI-6), and 12 months (SPI-12). These indices measure drought frequency and intensity, providing parameters for the multiscale Drought Hazard Index (DHI) to identify areas at risk during specific periods. Our analysis indicates that as drought periods lengthen, DHI intensity in each grid generally decreases. A distinct DHI pattern emerges in the tropical rainforest climate zone (Af) in Southeast Asia, while the Mediterranean climate (Csb) in southwestern and southeastern Australia exhibits the largest proportion of very high hazard across all drought periods. Overall, the 3-month period presents the highest drought hazard in both Southeast Asia and Australia. Keywords: Spatial Analysis- Southeast Asia- Australia- Drought Hazard Index- Meteorological Drought- SPI. Share Link | Plain Format | Corresponding Author (Imam Maulana Yosa)

18	Atmospheric Sciences	ABS-94
Premium Climate Services for Mining Company, How Good is It? Supari(a)*, Alexander Eggy Christian Pandiangan(a), Ahmad Baiquni(b), Robi Muharsyah(a), Indra Gustari(a), Amsari Muzakir Setiawan(a), Adi Ripaldi(a), Alif Akbar Syafrianno(a), Fatchiyah(a), Dian Nur Ratri(a), Niken Wahyuni(a), Tiar Maharani(a), Adyaksa Budi Raharja(a), Novi Fitrianti(a), Arda Yuswantoro(a), Fathiya Nurrahmanita(a), Diah Ariefianty(a), Syahru Romadhon(a), Mia Rosmiati(a), Suci Pratiwi(a), Hasalika Nurjannah(a), Dyah Ayu Kartika(a), and Yohanes Agung Kristomo(a) a) Indonesia Agency for Meteorology, Climatology and Geophysics (BMKG), Jakarta, Indonesia b) PT Berau Coal, Berau, East Kalimantan, Indonesia Abstract In recent years, the BMKG (Indonesian Meteorological, Climatological, and Geophysical Agency) has provided premium climate services to PT Berau Coal, including 10-day and monthly rainfall forecasts. These services are crucial for mining operations in preparing work plans, as rainfall can make roads at the mining site slippery, leading to reduced effective working hours, increased pump operating hours, and higher fuel costs. This study evaluates the performance of ECMWF monthly rainfall predictions for three mining sites (Sambarata, Lati, and Binungan) over the period 2005-2023, based on the availability of rainfall observation data at the mining sites, using the RMSE metric. The analysis shows that for a lead time of one (six) month, i.e., a forecast given one (six) month in advance, the average RMSE is 94 (95) mm/month. The highest error is observed in January, at 140 (144) mm/month, while the lowest error occurs in August, at 65 (69) mm/month. These results indicate that the climate service forecasts have reasonably good accuracy and can be used as a reference in decision-making, although potential errors, as indicated by the RMSE values, should still be considered. Keywords: Skill,Rainfall Forecast, Mining site, Climate Services Share Link | Plain Format | Corresponding Author (Supari )

19	Interdisciplinary Earth Science and Technology	ABS-1
Analysis of Variables Affecting Land Value in Earthquake-Prone Areas, Lembang Fault Zone (Case Study: Bandung City, West Java Province) Muhammad Saddam Maladi (a), Alfita Puspa Handayani (a*), Riantini Virtriana (b) a) Spatial and Cadastre System Research Group, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, Bandung, Indonesia *alfita[at]itb.ac.id b) Geographic Information Science and Technology Research Group, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, Bandung, Indonesia Abstract Bandung City, located in West Java, Indonesia, faces a high risk of earthquake disasters due to its proximity to the Lembang Fault. This active shear fault contributes to the vulnerability of the area to earthquakes because of its unstable fault activity. However, it is important to note that despite this seismic risk, earthquake disasters are not considered a determining factor for land valuation according to the competent authority and the issuance of the Land Value Zone (ZNT) Map. To better understand the variables affecting land value in Bandung City as an Earthquake-Prone Area, this study employed a Geographic Information System (GIS)-based approach known as Spatial Multi-Criteria Evaluation (SMCE). The study aimed to model a Land Value Estimation Map by considering four categories of factors: Social Factors, Economic Factors, Government Factors, and Physical Factors. Using the Analytic Hierarchy Process (AHP), the study assessed land value based on expert opinions gathered through a questionnaire targeting professionals in cadastral, land, and tax assessment. Based on the results, the models which consider the Earthquake-Disaster aspect have lower land values than the actual field circumstances. This finding suggests that the high risk of earthquakes does not significantly impact the market value of land in Bandung City. Keywords: Earthquake-Prone Area, Lembang Fault Zone, Land Value, Analytic Hierarchy Process (AHP), Spatial Multi Criteria Evaluation (SMCE) Share Link | Plain Format | Corresponding Author (Muhammad Saddam Maladi)

20	Interdisciplinary Earth Science and Technology	ABS-2
DIVERSION TUNNEL WALLS STABILITY ANALYSIS USING FINITE ELEMENT METHOD AT TIGA DIHAJI DAM CONSTRUCTION, SOUTH OGAN KOMERING ULU, SOUTH SUMATERA PROVINCE Panji Krisdianto (a*), Hendy Setiawan (b), Wawan Budianta (b) a) Department of Geological Engineering, Faculty of Engineering, Universitas Gadjah Mada, Yogyakarta, Indonesia *panji.krisdianto[at]mail.ugm.ac.id b) Department of Geological Engineering, Faculty of Engineering, Universitas Gadjah Mada, Yogyakarta, Indonesia Abstract The diversion tunnel is one type of tunnel in the Tiga Dihaji dam construction that used for diverting the river flow along the main dam construction. The diversion tunnel uses a tunnel construction design with a diameter of 7 meters and a tunnel length of 595 meters consisting of several construction elements including the tunnel walls along the trace. It is necessary to study the stability of the tunnel walls to ensure that the walls are sufficiently stable after the construction is finished and all the supports system are already installed. Analysis of the stability of the tunnel walls is carried out using the Finite Element Method (FEM) with a 2D model to obtain the Safety Factor (SF) and total displacement value. To support the tunnel walls stability analysis, it is necessary to conduct laboratory tests to determine several parameters including the Uniaxial Compression Strength (UCS) value, cohesion value and inner shear angle value. In addition to laboratory tests, rock mass classification using the Geological Strength Index (GSI) method were conducted and the properties of the supports system was defined as one of the main inputs to obtain the Safety Factor and total displacement value. As the result, the tunnel walls Safety Factor value is more than 2 and the total displacement value is below 10 cm. Both results of the walls stability analysis show that the diversion tunnel is on a stable condition after the construction and there is no need to add or modify the support system that already installed. Keywords: Diversion Tunnel, Walls Stability, Finite Element Method, Safety Factor, Total Displacement Share Link | Plain Format | Corresponding Author (Panji Krisdianto)

21	Interdisciplinary Earth Science and Technology	ABS-3
ENGINEERING GEOLOGICAL STUDY TO DETERMINE EXCAVATION METHODS AND SUPPORT SYSTEMS IN ALTERNATIVE PLANNING 1 CONSTRUCTION OF THE BODRI DAM DIVERSION TUNNEL, KENDAL DISTRICT, CENTRAL JAVA PROVINCE Kurnia Sandi Mahardhika (a), I Gde Budi Indrawan (b), Nugroho Imam Setiawan (c) (c (a) Gadjah Mada University, Department of Geological Engineering, Yogyakarta, Indonesia e-mail : kurniasandimahardhika[at]mail.ugm.ac.id (b) Gadjah Mada University, Department of Geological Engineering, Yogyakarta, Indonesia e-mail : igbindrawan[at]ugm.ac.id (c) Gadjah Mada University, Department of Geological Engineering, Yogyakarta, Indonesia e-mail : nugroho.setiawan[at]ugm.ac.id Abstract During dam construction, there are tunnels in the diversion channel which are very important to study technically. In 2018, the Organization River Basin of Pemali Juana carried out activities in the form of a feasibility study on the Bodri Dam. The feasibility study did not explain the excavation method and support system to be used in the Bodri Dam diversion tunnel. Based on this, this research examines the appropriate excavation methods and support systems to use based on the engineering geological characteristics that exist in the area around the Bodri Dam diversion tunnel alignment. The results of this research can provide input excavation methods and tunnel support systems for planning the construction of the Bodri Dam bypass tunnel on alternative route 1. The research method used in this research is to carry out technical geological mapping in the area around the alternative Bodri Dam bypass tunnel alignment for primary data collection. Secondary data collection was carried out on drilling results from planning consultants at Organization River Basin of Pemali Juana. Laboratory tests were carried out on surface samples and drilling samples. Determining the excavation method based on the excavability graph (Pettifer and Fokes, 1994) shows that the dominant excavation methods are easy digging and hard digging. Determining another excavation method to be used is based on the Rock Mass Rating (Bienawski, 1989), which shows that the appropriate excavation method results are by making a top heading and bench and installing supports along with excavation 10 m from the face of the excavation. Determination of the buffer system is divided into 3 areas, namely inlet, middle and outlet. The tunnel inlet outlet and middle require supports, namely shortcrete, rock bolts, wire mesh, steel sets, and fiber reinforced sprayed concrete. Keywords: Engineering Geological, Excavation Method, Support System Share Link | Plain Format | Corresponding Author (Kurnia Sandi Mahardhika)

22	Interdisciplinary Earth Science and Technology	ABS-4
Groundwater Genesis Determination Using Stable Isotope Data and Hydrochemistry in the Bali Cultural Center and Surroundings Gingin Sugriansyah (a*), Heru Hendrayana (a), Pulung Arya Pranantya (b) a) Department of Geological Engineering, Faculty of Engineering, Gadjah Mada University *ginginsugriansyah[at]mail.ugm.ac.id b) Directorate of Groundwater and Bulk Water, Directorate General of Water Resources, Ministry of Public Works and Housing Abstract The Bali Cultural Center, located in Klungkung Regency, Bali Province, is currently being developed to support the increase in tourism and as an effort to preserve Balinese culture. The Bali Cultural Center spans 334.62 hectares and will feature facilities designed to showcase Balinese diverse cultural heritage. In order to meet the water needs in this area, the Tukad Unda Reservoir is being constructed, which is also projected to meet the water needs in the Klungkung and Karangasem Regencies. The approach in this study involves integrating hydrochemical analysis and stable isotope data 18O and 2H, which are tested using the cavity ringdown spectrometer method to understand the hydrogeological system linkage in the geological complex of the Bali Cultural Center and its surroundings. A total of 24 hydrochemical test samples and 16 stable isotope test samples were collected spatially from various water sources, including rainwater, springs, shallow groundwater, and deep groundwater, from different rock formations. The results of this study indicate the origins of the groundwater in the Bali Cultural Center and its surroundings, as well as the characteristics of the aquifers that make it up. This information is important in order to protect the sustainability of the recharge areas, so as to achieve sustainable use of groundwater. The hilly region north of the Bali Cultural Center is considered a recharge zone for springs and deep groundwater. Furthermore, shallow groundwater is replenished by recharge areas at lower elevations and continues to be affected by surface water conditions. Keywords: Bali Cultural Center, Stable Isotopes, Hydrochemistry, Recharge Area Share Link | Plain Format | Corresponding Author (Gingin Sugriansyah)

23	Interdisciplinary Earth Science and Technology	ABS-5
Assessment of Implementation of Customary Land Administration Principles and Its Benefits for Land Administration in Indonesia Rizqi Abdulharis Institut Teknologi Bandung Abstract Since 1960 Indonesia has shifted its land administration to an indigenous one, which was claimed to be developed based on the customary land administration principles in Indonesia. The adaptation of customary land administration was chosen (Harsono, 2013) because they have been proven to be able to maintain the sustainability of the indigenous territories in Indonesia (Abdulharis, 2014). This is clearly stated in the 1960^s Basic Agrarian Act, which is considered as one of the important milestones on the development of land administration system in Indonesia. While land administration comprises of processes with regard to land tenure, land use, land development and land value (Williamson et al., 2011), the 1960^s Basic Agrarian Act only regulates land tenure process. Land use, land development and land value processes are regulated by other regulations, which were enacted after the promulgation of the 1960^s Basic Agrarian Act. Such facts raise a question whether land use, land development and land value regulations comply with the 1960^s Basic Agrarian Act, particularly concerning the implementation of customary land administration principles in Indonesia. Most importantly, relevancy of customary land administration principles to regulate the modern land administration in Indonesia has also been questioned. To answer the first question, the formal land administration system is compared with the customary land administration system. Moreover, the second question is expected to be answered by assessing the benefits of the application of customary land administration principles in land administration in Indonesia. The research that is highlighted in this manuscript was implementing multiple case study approach to identify the customary land administration principles. The case study areas were West Sumatera, West Java and Maluku. The primary data was collected by means of key informant interviews and visual ethnography. The analysis was done by secondary data analysis, content analysis and classificational analysis. The result of the comparison between customary and formal land administration in Indonesia shows that there are contradictions between principles that are applied in the aforementioned systems. Even, the rights of indigenous communities have only been partially protected. Furthermore, benefits of the application of customary land administration principles in Indonesia have also been identified. These findings are valuable on the enhancement of formal land administration system of Indonesia. Keywords: Custom, Indonesia, Land Administration Share Link | Plain Format | Corresponding Author (Rizqi Abdulharis)

24	Interdisciplinary Earth Science and Technology	ABS-6
Surviving the Ring of Fire: Women^s resilience in Multi-Hazard Environments Alfita Puspa Handayani, Chikako Isouchi Institut Teknologi Bandung, Kagawa University Abstract Living within the volatile Ring of Fire poses unique challenges, particularly for women in multi-hazard environments. This paper delves into the lived experiences of women in such regions, highlighting their coping strategies and resilience. It begins with an introduction to the Ring of Fire, outlining its geological significance and common hazards like earthquakes, volcanic eruptions, and tsunamis, while emphasizing gender-specific vulnerabilities. Through case studies and personal narratives, the paper examines the gendered roles and responsibilities in disaster management and the challenges faced by women during prevention, preparedness, response, and recovery phases. Furthermore, it explores the adaptive strategies and community resilience fostered by women, underscoring the importance of social support networks. The discussion extends to opportunities for women^s empowerment in disaster risk reduction, advocating for gender-sensitive policies and initiatives. The paper concludes by stressing the necessity of addressing gender-specific vulnerabilities and promoting collective action to support and empower women in multi-hazard environments. Keywords: women empowerment, disaster risk reduction, resilience, multi hazard Share Link | Plain Format | Corresponding Author (Alfita Puspa Handayani)

25	Interdisciplinary Earth Science and Technology	ABS-7
Finite Element Method of Slope Stability Analysis: Case Study of Inlet Portal in the Diversion Tunnel of Bagong Dam, East Java, Indonesia Ganny Indrajid (a,b*), Hendy Setiawan (a), Wahyu Wilopo a) Department of Geological Engineering, Faculty of Engineering, Universitas Gadjah Mada, Yogyakarta 55281, Indonesia b) Ministry of Public Works and Housing, Jakarta, Indonesia * gannyindrajid[at]mail.ugm.ac.id Abstract Construction of the Bagong Dam^s diversion tunnel commenced in 2022. The tunnel, stretching 480 meters in length and measuring 4 meters in dimensions, is positioned directly beneath the dam. Due to the change in the trajectory of the inlet portal, a thorough analysis of the slope stability of the inlet portal is essential. This report presents a comprehensive slope stability analysis using the finite element method (FEM), both with and without earthquake loading. It also includes data for FEM analysis such as subsurface lithology, drill core analysis, observations of the geological strength index (GSI), and pertinent laboratory results. The study area encompasses two main lithologies: slightly weathered calcipulverite limestone and moderately weathered andesite breccia with interbedded claystone. GSI observations on core drill samples indicate that calcipulverite limestone is poor to fair quality (21 until 55), and andesite breccia with interbedded claystone is poor to good quality (21 until 75). The results of the FEM analysis showed that the Critical Strength Reduction Factor (SRF) of the slope decreased after adding earthquake loads. Under static and earthquake loads, the excavated slope at the tunnel inlet with a slope of 45 degree has a critical SRF value of 2,2. Based on the calculated SRF value, it can confidently affirm that the condition of the inlet portal slope is safe. Keywords: slope stability, inlet portal, geological strength index, finite element method, strength reduction factor Share Link | Plain Format | Corresponding Author (Ganny Indrajid)

26	Interdisciplinary Earth Science and Technology	ABS-8
A Method for Evaluating the Impact of Typhoon-Induced Rainfall in Taiwan under Climate Change Scenarios Based on Statistic Models Tsun-Hua Yang(a*), Hao-Lun Kuo(a), Chi-Ying Lin(a) a)National Yang Ming Chiao Tung University *tshyang[at]nycu.edu.tw Abstract Typhoon-induced rainfall is a significant water resource for the Northwest Pacific region. The amount of rainfall from a typhoon is closely related to the duration of the typhoon^s presence and its movement speed. Future climate change scenarios suggest that rising ocean temperatures will affect the formation of typhoons. In this study, statistical models such as the Negative Binomial distribution, Vickery Model, and Monte Carlo simulation were used to analyze changes in the total number of typhoons, frequency, typhoon genesis locations, path distributions, and wind field intensity under future climate change scenarios. A Bayesian network was then developed to predict typhoon-induced rainfall. The network includes a directed acyclic graph to visually represent the relationships between typhoon-induced rainfall and typhoon characteristics such as typhoon radius, intensity, wind speed, and location. For validation of the statistical models, this study selected 30 rainfall gauges across Taiwan island and used typhoon data from 1977 to 2022 and rainfall data from 2010 to 2021. Finally, the study assessed the potential impacts of typhoon-induced rainfall on a categorized basis towards the middle and end of the century under a high-emission climate change scenario (RCP 8.5). Keywords: Climate change- Typhoon rainfall- Statistical approach- Bayesian network Share Link | Plain Format | Corresponding Author (Tsunhua Yang)

27	Interdisciplinary Earth Science and Technology	ABS-13
Empirical satellite imagery-based models to enable and assess the current state of surface freshwaters Yuli Sudriani(a*), Ridho Ismanto(a), Intan Nuni Wahyuni(a), Meti Yulianti(b), Arie Vatresia(c), Arnida Lailatul Latifah(a,d) a) Research Center for Computing, National Research and Innovation Agency (BRIN), Indonesia *yuli038[at]brin.go.id b) Research Center for Water Resource and Limnology, National Research and Innovation Agency (BRIN), Indonesia c) University of Bengkulu, Indonesia d) School of Computing, Telkom University, Indonesia Abstract This study proposes an integrated analysis for evaluating the potential of eutrophication enrichment in Maninjau Lake as a case study based on a single trophic state index (TSI) of surface freshwater, namely carlson^s TSI chlorophyll-a (Chl-a). The spatio-temporal concentration of Chl-a is estimated from remote sensing data, specifically, Landsat-8 Operational Land Imager (OLI), and the technique is not trivial. There is no unique model that can quantify Chl-a in any surface freshwater. Therefore, we investigate various models, consisting of seventy-six existing equations, that represent empirical relationships between in-situ Chl-a measurements and the remote sensing reflectance ratio of the Landsat-8 bands. The structure of the equations includes linear, polynomial, exponential, and logarithmic relationships. Jenn-Fisher classification is used to cluster the result from carlson^s TSI Chl-a which provides more comprehensive analysis in each zone. The model evaluation is based on the reliability of its range and correlation with in-situ data. By combining remote sensing monitoring and an integrated algorithms, the presented research has identified the optimal model and the spectral band combinations to estimate the Chl-a concentration patterns, which promisingly enables spatially and temporally automated assessment detection on a current-state basis. This finding is expected to enhance the effectiveness of the eutrophication monitoring system in multiple-locations, typical seasonality, and hydrogeomorphology, ultimately supporting the sustainability of watershed management. Keywords: satellite images, classification, chlorophyll-a, landsat equation, water quality monitoring, spatio-temporal monitoring Share Link | Plain Format | Corresponding Author (Yuli Sudriani)

28	Interdisciplinary Earth Science and Technology	ABS-14
The Role of Socio-Hydrogeology in Closing The Gaps Between Quantitative and Qualitative Approaches in Hydrogeological Mapping Dasapta Erwin Irawan, Arif Susanto, Deny Juanda Puradimaja, Astyka Pamumpuni, and Rendy Dwi Kartiko Applied Geology Research Group, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung Abstract Introduction: In numerous hydrogeological studies, the value of local knowledge concerning groundwater sources and contamination is often underestimated in favor of strictly scientific data. This oversight can result in an incomplete understanding of groundwater systems. Local communities possess valuable insights into seasonal variations, contamination origins, and historical water usage patterns that are not fully captured by scientific measurements alone. This perspective article shows the gaps between both quantitative and qualitative approach and how we can mixed those approaches to improve hydrogeological mapping in Indonesia. Methods: Scientific models are typically utilized to predict groundwater contamination risks based on parameters like land use and hydrological data. However, these models often fail to consider the community^s perception of these risks. For example, a community might perceive the threat of contamination from nearby industrial activities to be higher than what scientific models indicate. This discrepancy can lead to distrust in scientific findings and resistance to proposed management strategies. Discussions: Hydrogeological mapping generally focuses on the physical availability of groundwater resources, often overlooking the specific needs and priorities of local communities. For instance, a hydrogeological study might determine that an area has adequate groundwater for agricultural purposes, yet may fail to recognize that the local community prioritizes drinking water access over agricultural use. This misalignment can lead to conflicts and inefficient resource allocation. Keywords: hydrogeology, socio-hydrogeology, quantitative approach, qualitative approach Share Link | Plain Format | Corresponding Author (Dasapta Erwin Irawan)

29	Interdisciplinary Earth Science and Technology	ABS-15
Impact of ENSO on the Variability of Electricity Production at a Hydropower Plant in Bakaru Sulawesi, Indonesia Siti Khairani P Sari (a,b*), Ivonne M. Radjawane (c), Muhammad Rais Abdillah (d), Dwina Nugraha (a), Syahandra Ramadhan (a) a) Earth Science Masters Program, Faculty of Earth Science and Technology, Institut Teknologi Bandung *itiskhairani[at]gmail.com b) Operations Risk Management Division, PT PLN (Persero) c) Oceanography Research Group, Faculty of Earth Science and Technology, Institut Teknologi Bandung d) Atmospheric Science Research Group, Faculty of Earth Science and Technology, Institut Teknologi Bandung Abstract El Nino-Southern Oscillation (ENSO) is a large-scale interaction of ocean and atmosphere that manifests itself as fluctuations in ocean surface temperature and air pressure in the tropical Pacific Ocean. The impact of ENSO has been felt worldwide, including in the energy sector. Changes in sea surface temperature and rainfall patterns can affect the drainage of river and lake water used for hydroelectric power generation. Pembangkit Listrik Tenaga Air (PLTA) is one type of power plant that uses potential energy of water into kinetic energy which is then used to move turbines and generate electricity. Here we investigate the impact of ENSO on the availability of primary energy available in the Bakaru PLTA, South Sulawesi during 2011-2023. A correlation coefficient of -0.35 was obtained from Spearmans correlations test results between ONI with anomalies of discharge and monthly electricity production, implying that during El Nino (La Nina) the electricity production tend to lower (higher) than usual. The negative correlation is consistent with the common relationship between Indonesia rainfall and ONI. From climatological analysis, in 2015 (El Nino) and 2022 (La Nina) the discharges and electricity generation were consistently lower in 2015 (-42.19 m3/s and -29.43 GWh) and higher in 2022 (67.47 m3/s and 39.37 GWh) compared to its climatological data. A better understanding of the impact of ENSO on the availability of primary energy on PLTAs can improve the predictability of future electricity supply. Keywords: ENSO- Hydropower Plant Share Link | Plain Format | Corresponding Author (Siti Khairani Permata Sari)

30	Interdisciplinary Earth Science and Technology	ABS-16
The Influence of ENSO on electricity production in Cirata hydro power Reza Kurniawan Harnandika(*1,4), Muhammad Rais Abdillah(2), Ivonne M. Radjawane(3), Liza Kurniawan Mansur(1), Zuhda Nur Prabowo(1) *) cloudyreza[at]gmail.com 1) Earth Science Masters Program, Faculty of Earth Science and Technology, ITB 2) Atmospheric Science Research Group, Faculty of Earth Science and Technology, ITB 3) Oceanography Research Group, Faculty of Earth Science and Technology, ITB 4) UIP2B Java-Bali, PT PLN (Persero) Abstract This study examines the influence of El Nino Southern Oscillation or ENSO on electricity production at the Cirata hydroelectric power plant in West Java, Indonesia from 2010 to 2023. Using data on ENSO indices, precipitation, reservoir water levels, and electricity production, the research analyses correlations between these variables during different seasons. Results show that ENSO has a strong negative correlation with rainfall in the study area, particularly during the June to November dry season. Rainfall, in turn, positively correlates with reservoir water levels and power generation. While ENSO does not directly determine hydropower output, it indirectly impacts production by affecting precipitation patterns and water availability. The study finds that El Nino events generally correspond to decreased rainfall and lower electricity generation at Cirata, while La Nina tends to increase precipitation and power output. However, the relationships are complex and vary seasonally. The strongest correlations occur during the southeast monsoon (June to August) and transitional period (September to November). Despite ENSO related fluctuations, Cirata maintained relatively stable operations, likely due to effective reservoir management and preserved watershed conditions. The research highlights the importance of monitoring ENSO forecasts and optimising water resource management to mitigate impacts on hydropower generation. It recommends strategies such as enhancing water storage during wet periods, improving operational efficiency, and diversifying energy sources to increase resilience to climate variability. Overall, the study provides insights to support long term planning and sustainable management of hydroelectric resources in Indonesia. Keywords: ENSO, Hydroelectric, Power production and Climate variability Share Link | Plain Format | Corresponding Author (Reza Kurniawan Harnandika)

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