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91	Ocean-Atmosphere Dynamics	ABS-49
The Effects of the Indonesian Throughflow, River, and Tide on Physical and Hydrodynamic Conditions During the Wind-Driven Upwelling Period North of the Aru Islands Abdul Basit(1), Bernhard Mayer(2), Thomas Pohlmann(2) National Research and Innovation Agency Republic of Indonesia(BRIN) Hamburg University Abstract A three-dimensional baroclinic nonlinear numerical model-the Hamburg Shelf Ocean Model (HAMSOM)-was applied to investigate the effects of the Indonesian throughflow (ITF), river runoff, and tidal forcing on circulation during the southeast monsoon period (July 2004) north of the Aru Islands by conducting different sensitivity runs. It was found that the Ekman transport over the continental slope of the Sahul Shelf was the main factor that causes upwelling north of the Aru Islands, and this was suggested to be one of the main factors behind the surface water in the research area being relatively colder and saltier than the surrounding waters. The influence of South Pacific Subtropical Water (SPSW) on the surface water was indicated by the high surface salinity of waters within the internal salinity maximum layer. The results also suggested that onshore subsurface currents over the slope were induced not only by offshore surface currents over the slope but also by the ITF. By considering the eastern ITF route, river runoff and tidal forcing were also found to contribute significantly to the erosion of the salinity maximum (approx. 0.25) within the Halmahera Sea, thereby reducing sea surface salinity north of the Aru Islands. Furthermore, it was proposed that river runoff from the western coast of Papua Island contributed to intensified cross-shelf circulation over the continental slope. These conditions were related to enhancing vertical viscosity forces in the surface waters induced by stronger stratification as an impact of river inclusion in the simulation. Keywords: Aru Islands, river, tide, upwelling, wind Share Link | Plain Format | Corresponding Author (abdul basit)

92	Ocean-Atmosphere Dynamics	ABS-51
Tropical cyclones and its impact on seasonal downwelling/upwelling in southern Indonesia waters Avrionesti, M. RIdwan Prasetya, M. Riam Badriana Sekolah Tinggi Meteorologi Klimatologi dan Geofisika Abstract The southern region of Indonesia is one of the places where tropical cyclones grow in the southern hemisphere. In the period 1992 - 2022 there were approximately 216 tropical cyclones that occurred in the southern waters of Indonesia with 85 of them falling into the category of cyclones 1 - 5 based on Saffir-Simpson scale. Apart from cyclones, southern Indonesia waters also experienced other oceanographic phenomena, seasonal upwelling and downwelling. This study aims to determine the effect of cyclones on physical conditions in southern Indonesia waters during the seasonal upwelling/downwelling period. Historical data shows that tropical cyclones in southern Indonesia generally occur in the DFJ month and almost never occur in the JJA month. Meanwhile, the upwelling (downwelling) period occurs during the JJA (DJF) season. The results show that in general, cyclones cause mixing in the upper layers of the sea, although it does not always have an impact on the emergence of upwelling in the path they pass. Keywords: cyclone, downwelling, upwelling Share Link | Plain Format | Corresponding Author (Avrionesti Avrionesti)

93	Ocean-Atmosphere Dynamics	ABS-54
Characteristics of Water Mass in The Flores Sea: The Effect of The ITF on The Transitional Season Engki A. Kisnarti (a*), Ima Nurmalia Permatasari (a), Dwi Sukma Wahyuni (b) (a) Program of Oceanography, Faculty of Engineering and Marine Science, Hang Tuah University, Surabaya-Indonesia *engki.andri[at]hangtuah.ac.id (b) Student of Oceanography Study Program, Faculty of Engineering and Marine Science, Hang Tuah University, Surabaya-Indonesia Abstract Indonesian Through Flow (ITF) forms a distinctive water mass characteristics in Indonesian Sea Waters. This mass of water enters through the Makassar Strait to the Banda Sea by crossing the Flores Sea. This study aims to analyze the characteristics of the water masses in the Flores Sea during the transitional season. In analyzing the type of water mass using the T-S diagram the results of data processing using Matlab. This study used CTD data from the Jala Citra Expedition 3-2023 in the Flores Sea waters organized by the Indonesian Navy^s Hydro-Oceanographic Center. Processing data was taken April-May 2023, there were 5 station points. The results of the data Jala Citra 3-2023 which were analyzed using the T-S diagram contained 3 types of characteristics of the first water mass, Bengal Bay Water (BBW) starting from the surface to a depth of 70 m. Second, the characteristics of the Eastern South Pacific Central Water (ESPCW) water mass, while the minimum extreme value of the Flores Sea has a low salinity water mass value. Third, the water mass of Western South Pacific Central Water (WSPCW) was found. The origin of the water mass in the Flores Sea is from North Pacific Subtopical Water (NPSW) and North Pacific Intermediate Water (NPIW). Keywords: Flores Sea, ITF, water mass characteristics Share Link | Plain Format | Corresponding Author (Dwi Sukma Wahyuni)

94	Ocean-Atmosphere Dynamics	ABS-62
The development of high-resolution wave model in the Indonesia^s Inner Seas: Sunda Strait sea-state during Dahlia Tropical Cyclone event Muhamad Farid Geonova (a*), S R Adiprabowo (a), A Rahman (a), S Prasetyo (a), A Ramdhani (a), A P Widyani (b), A Amalya (b), E Prasetyo (a) a)Agency for Meteorology Climatology and Geophysics (BMKG), Indonesia. Jl. Angkasa 1 No.2, RT.1/RW.10, Gn. Sahari Sel., Kec. Kemayoran, Kota Jakarta Pusat, Daerah Khusus Ibukota Jakarta 10610 *muhamad.geonova[at]bmkg.go.id b)Department of Oceanography, Diponegoro University, Indonesia. Jl. Prof. Sudarto No.13, Tembalang, Kec. Tembalang, Kota Semarang, Jawa Tengah 50275 Abstract The accurate representation of wind waves is crucial for shipping safety, understanding coastal dynamics, assessing coastal vulnerability, and supporting various marine activities. Various efforts have been made in understanding and predicting the ocean wave condition through numerical modeling. In this study, we present the development and application of a high-resolution (~1km) wind wave model using the SWAN (Simulating Waves Nearshore) model for the Sunda Strait, Indonesia during the Tropical Cyclone Dahlia event in 2017. Our focus is on investigating the impact of Tropical Cyclone Dahlia on local wave conditions. The Sunda Strait, located between Java and Sumatra, plays a vital role in maritime transportation, coastal infrastructure, and coastal ecosystems. Accurate wave forecasts in this region are essential for ensuring safe navigation, coastal management, and disaster preparedness. We employ the SWAN model, a third-generation wave model, capable of simulating wind wave spectra under varying environmental conditions. High-resolution input data, including atmospheric reanalysis for wind fields and bathymetric data, are utilized to drive the model. We present a thorough analysis of the wave characteristics, including significant wave height, wave direction, and wave period, during the passage of Tropical Cyclone Dahlia. The high-resolution wind wave model, based on SWAN, exhibits excellent performance in simulating wave conditions in the Sunda Strait, Indonesia. The study provides essential information on the impact of Tropical Cyclone Dahlia on the local wave condition especially in Sunda Strait, also contributing to the improvement of early warning systems, coastal management and disaster preparedness efforts. Keywords: high-resolution model, wind-wave, tropical cyclone, extreme events Share Link | Plain Format | Corresponding Author (Muhamad Farid Geonova)

95	Ocean-Atmosphere Dynamics	ABS-65
STUDY OF CLIMATE CHANGE HAZARDS USING THE CLIMATE HAZARD INDEX IN INDONESIA Ismail Robbani, Joko Wiratmo, Armi Susandi Faculty of Earth Science and Technology Institut Teknologi Bandung Abstract Climate change is a serious problem that must be faced by the world. This impacts ecosystems and people in all parts of the world^s continents and oceans and poses grave risks to human health, global food security and economic development. One of the steps to reduce climate change disasters is climate risk management. Climate Risk Index (CRI) is a quantitative calculation of one or many climate risks with thresholds specific to extreme weather and climate events that cause disasters. One of the stages in preparing the CRI is to determine the hazard value index or Climate Hazard Index (CHI). Because the climatic conditions in Indonesia vary with rainfall, it is necessary to conduct a study to determine the CHI associated with this variable. In this study, climate hazards are defined as hazards that are directly related to the climate in Indonesia, namely rainfall. The hazard events studied are drought and extreme rain. Then the constituent components of the CHI studied are the drought index and the extreme rain index. Hazard studies in Indonesia show that there is an increasing trend in each of the CHI component indexes with a very high frequency of hazard events occurring frequently from 1995 to 2021. June is the month that has the highest average CHI among other months throughout the year 1962-2021. In terms of spatial patterns, CHI is extreme in the Indonesian region with local and equatorial rainfall patterns. Whereas in the monsoon pattern, CHI is in the medium-very low range. Furthermore, CHI can be influenced by several factors, one of which is forest land cover. The results show that when the loss of forest land cover increases, the CHI value and its component index will also increase in the short term. Keywords: Hazard, Climate change, Climate Hazard Index, Indonesia Share Link | Plain Format | Corresponding Author (Joko Wiratmo)

96	Ocean-Atmosphere Dynamics	ABS-69
Ocean Circulation and Variability in the Seram and Northern Banda Seas Amanda Christin Dompeipen (a*), Agus S Atmadipoera (b), Nabil Balbeid (b), Apriansyah (c), Delta Richelly Rumohoira (a), Dwiyoga Nugroho (d), Natih M N Natih (b) a) Graduate Magister program in Marine Sciences, Faculty of Fisheries and Marine Sciences, IPB University, 16680, Bogor, Indonesia *amanda.dompeipen[at]apps.ipb.ac.id b) Marine Science and Technology Department, Faculty of Fisheries and Marine Sciences, IPB University, 16680, Bogor, Indonesia c) Marine Science Program, Faculty of Mathematics and Natural Sciences, Tanjungpura University, 10340, Pontianak, West Kalimantan, Indonesia d) Research Center for Oceanography, National Research and Innovation Agency, 10340, Central Jakarta, DKI Jakarta, Indonesia Abstract The Seram and Banda Seas (SBS) convey the eastern pathway of Indonesian Throughflow (ITF) from Maluku and Halmahera inflow portals. This study aims to investigate circulation and variability at near surface (25 m) and thermocline (110 m) layers in the SBS region, using validated INDESO model output datasets (2008 to 2015). It is shown that much warmer and saltier thermocline ITF water from Halmahera is predominat, flowing southward and impinging northern coast of Seram near 128.5E. The flows then bifurcate eastward into the Banda outer ring arc and westward into Banda via Manipa Strait and western Seram Seas. In Banda, two clockwise eddies are found related to these inflows. Secondary southward inflow via Lifamatola is associated with cooler and less salty water, which merges with ITF Halmahera. The variability of oceanographic parameters is dominated by annual period. However, on interannual scale, the response of seawater temperature on ENSO is evident, and its amplitude is much stronger in Banda rather than in Seram. A decrease trend of seawater temperature is also found in the last 5 year datasets. Keywords: Seram and Banda Seas, Indonesian Throughflow, INDESO model, ocean circulation, ocean variability Share Link | Plain Format | Corresponding Author (Amanda Christin Dompeipen)

97	Ocean-Atmosphere Dynamics	ABS-71
Investigation of Mesoscale Eddies Properties in the Southeastern Tropical Indian Ocean: A Comparison between Altimetry and Reanalysis Data M. Rizqi Ramadhan (a*), Rahaden Bagas Hatmaja (b) a) Oceanography Department, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung, Indonesia. *rizqiramadhan.23112001[at]gmail.com b) Research Centre for Climate and Atmosphere, National Research and Innovation Agency (BRIN), Bandung, Indonesia. Abstract The southeastern tropical Indian Ocean (SETIO) is characterized by high mesoscale eddies activity, as the result of baroclinic instabilities that are associated with the South Java Current (SJC), South Equatorial Current (SEC), and Indonesian Throughflow (ITF), which play a key role in ocean dynamics, environment, and bio-system of this region. Satellite altimetry data and the GLORYS12V1 CMEMS reanalysis ocean product were used to investigate the features of mesoscale eddies in the SETIO. An autonomous eddy tracking system was used to identify the eddies. Along 2019, a total of 263 and 217 eddies were spotted and tracked based on satellite and reanalysis data, respectively. The results elucidates that the analysis of mesoscale eddies variability in ocean reanalysis data shows consistent manner with altimetry observations. Cyclonic eddies appeared to be more abundant and smaller compared to anticyclonic eddies. Larger amplitudes and radii are related with high eddy kinetic energy zones near the SJC, SEC, and ITF outflow. Furthermore, this study strengthens the quantitative understanding of mesoscale eddies dynamics in this region, including eddy formation and propagation. Keywords: mesoscale eddies- Southeastern Tropical Indian Ocean- reanalysis ocean data- altimetry Share Link | Plain Format | Corresponding Author (M Rizqi Ramadhan)

98	Ocean-Atmosphere Dynamics	ABS-75
Transport and transformation of intrinsic material within the Indonesian Seas Faisal Hamzah (a*), Zhimian Cao (b), Minhan Dai (b) a) Research Center for Oceanography, The National Research and Innovation Agency, Indonesia * faisal.hamzah[at]brin.go.id b) State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, China Abstract The Indonesian Seas is the only low-latitude gateway of water movement between the Pacific and Indian Oceans and plays a significant role in global climate change and freshwater balance. Much less known is the material transport (i.e., nutrient and carbon) along the Indonesian throughflow (ITF) and how material transformation would affect the regional seawater chemistry and subsequently ecosystem health. We observed that the ITF water supply from the Pacific had lower nutrient levels than what is required for sustainable biodiversity and marine productivity. In contrast, nutrient flux at the main outflow passage of ITF showed a slightly higher and act to enrich the nitrate to phosphate ratio of the Indian Ocean. The net nitrate flux associated with the ITF is estimated to be significant. Physical processes i.e., vertical diffusion and advection, exerted predominant controls and contributed to located elevated nutrients in the upper 100 m of Indonesian Seas. Other contributions to the Indonesian nutrient budget should be considered, including riverine runoff, upwelling, sediment, atmospheric deposition, and nitrogen fixation. Keywords: nutrient flux, Indonesian throughflow, transport, transformation Share Link | Plain Format | Corresponding Author (Faisal Hamzah)

99	Ocean-Atmosphere Dynamics	ABS-81
Interannual variations of Indonesian Throughflow in its main pathways produced by a data-assimilative ocean model Endro Soeyanto (a*), Yasumasa Miyazawa (b), Bayu Priyono (a) a) Research Center for Oceanography, National Research and Innovation Agency (BRIN), Kawasan Sains Aprilani Soegiarto, Jl. Pasir Putih 1, Ancol Timur, Jakarta 14430, Indonesia *endro.soeyanto[at]brin.go.id b) Application Laboratory, Japan Agency for Marine-Earth Science and Technology 3173-25 Showamachi, Kanazawa-ku, Yokohama City, Kanagawa 236-0001, Japan Abstract The interannual variability of sea surface height (SSH) and volume of water masses transport (volume transport) in the primary pathways of Indonesian Throughflow (ITF) and its relationships to the ocean dynamics between the western Pacific Ocean and eastern Indian Ocean associated with the El Nino Southern Oscillation (ENSO) phenomena was examined using the Japan Coastal Ocean Predictability Experiments Forecasting Global Ocean (JCOPE-FGO) reanalysis results from 1993 to 2013. The ENSO condition is represented by the sea surface temperature (SST) anomaly data of the Nino3.4 area (ENSO Index) obtained from NOAA. The variations of calculated interannual SSH and ocean current fields from the reanalysis results indicate their relations to ENSO conditions. The ENSO Index has a negative correlation to the interannual SSH difference between the western Pacific and eastern Indian Oceans. Meanwhile, the result of the correlation calculation of the ENSO Index to the volume transport in the main pathways of ITF shows an immediate (no lag) response at thermocline layers. During the strong ENSO periods, the changes in ocean current structures in the main pathways of ITF. Keywords: ITF, ENSO, interannual variations, JCOPE-FGO Share Link | Plain Format | Corresponding Author (Endro Soeyanto)

100	Ocean-Atmosphere Dynamics	ABS-82
Velocity profile and turbulence characteristics over coral reefs in Derawan Island, East Kalimantan Ayi Tarya, Faisal H. Muhammad and Nining Sari Ningsih Department of Oceanography Faculty of Earth Sciences and Technology Bandung Institute of Technology Abstract Turbulent boundary layer dynamics over coral reef communities control many biologically important processes, including food capture by benthic organisms, mass transfer of dissolved nutrients, larval dispersal, waste removal, and sediment transport. All of these processes are controlled by hydrodynamic mechanism are directly related to the shear and turbulent mixing. Motivated by the importance of boundary layer dynamics to both large and small scale ecological processes on coral reefs, this study aims to investigate velocity profiles, the turbulence parameters and boundary layer flow over a coral reef. Moored measurements on currents and turbulence were conducted at the three coral reef sites in Derawan Island, East Kalimantan. Velocity profiles were inferred from Acoustic Doppler Current Profilers (ADCP). The velocity data showed logarithmic profile up to ca. 3 meter from the bed, sometimes even up to nearby the surface (14 meter). Reynolds shear stresses and turbulent viscosities were derived from ADCP data by using the beam variance method. The data profiles showed fairly well with theoretical of previous study for the coral reef boundary layer. Boundary layer parameters, such as the friction velocity and roughness length, were determined by fitting a logarithmic profile to the velocity data. The time scale analysis showed that mesoscale fluctuations were present and the characteristic turbulence time scale varies an order of magnitude in time. Keywords: Velocity profiles, Boundary layer, Turbulence Share Link | Plain Format | Corresponding Author (Ayi Tarya)

101	Ocean-Atmosphere Dynamics	ABS-89
Ocean Net Primary Productivity Response to Seasonal and Interannual Climate Variability in the Southern East Java and East Nusa Tenggara Sea Region Muhammad Firman Nuruddin (1,2)- Mutiara Rachmat Putri*1 1. Department of Oceanography Faculty of Earth Sciences and Technology Bandung Institute of Technology 2. Ocean Science Department, School of Science, The Hong Kong University of Science and Technology Abstract The dynamics of ocean net primary productivity (NPP) in the Indonesian ocean are influenced by seasonal climate phenomena, monsoon trade wind, and inter-annual extreme variations, El-Nino Southern Oscillation (ENSO), as well as Indian Ocean Dipole (IOD). However, these complex interactions are still rarely explored in Southern Indonesian Sea areas. In this study, we use the NPP data from NEMO3.6-Pisces v2 model results, wind speed, and climate variability index (Dipole Mode (DMI) and Ocean Nino Index (ONI)) to elucidate the spatiotemporal variability of NPP along the Southern East Java and East Nusa Tenggara Sea region during the 1998 until 2018 period. Our analysis found that seasonal variation of NPP corresponded with the seasonal upwelling (downwelling) phenomena which happened during south (north) east monsoon period with the average magnitude of NPP varying between 339.30 and 567.20 mgCm-2day-1. Meanwhile, the climatological anomaly of the NPP in this region is more influenced by the interannual extreme event of the Indian Ocean Dipole compared to El-Nino Southern Oscillation as shown by the partial correlation value between NPP and DMI (ONI) 0.56 (0.28). Specifically, when IOD+ (-) occurred, there was positive (negative) increment on the ocean productivity anomaly. This study reveals an important relationship between annual-interannual climate phenomena and ocean primary production variability in a complex ocean region. Keywords: Net primary productivity, Monsoon, ENSO, IOD Share Link | Plain Format | Corresponding Author (Muhammad Firman Nuruddin)

102	Ocean-Atmosphere Dynamics	ABS-100
Spatial Distribution of Methane Flux in the North Coast of Java Island Case Study: Jakarta Bay Fadjar Hidajat a,c*, Nining Sari Ningsih b), A. R .Kartadikaria b), Irfan Kampono a), Y.I. Ulumuddin c), Agus Dendi Rochendic), Singgih P.A.W c), M.T.Kaisupy c), Nurjamin c), Muhadjirin c) , Raden Sutiadi c) , Lusyana c) a) Earth Science Study program of Oceanography, ITB, Jl. Ganesha 10 Bandung 40132, Indonesia b) Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Jl. Ganesha 10, Bandung 40132, Indonesia c) Research Center for Oceanography, National Research and Innovation Agency (BRIN), Jl. Pasir Putih 1, Ancol Timur, North Jakarta 14430, Indonesia *E-mail: fadj003[at]brin.go.id Abstract Methane (CH4) is the second most potent greenhouse gas (GHG) in terms of global warming and climate change after carbon dioxide (CO2). Its concentration in coastal areas is strongly influenced by anthropogenic activities, especially from waste products that go directly into the rivers. Jakarta Bay is the outlet of several rivers that flow through populated areas- thus, it is very likely the water carries a form of contaminants including nutrients and organic matter. This zone is vulnerable to hypoxia, low concentation or without oxygen in water, that would cause an increase in the concentration of methane in the coastal sediments of the methanogenesis zone and the process of releasing CH4 into the water column and the atmosphere. The hypoxic condition of the waters is thought to be a potential source of dissolved CH4. According to the concept of the ^CH4 Paradox^ in which previous studies have revealed that CH4 is only found in zones that do not contain oxygen. Since in the aerobic seawater condition oxygen could convert methane (CH4) into carbon dioxide and water (H2O). The methane therefore slowly breaks down during its journey from the seabed up through the seawater. The greater the depth from which the methane rises, the farther it has to travel and the less methane reaches the upper water layers and the atmosphere. However, in recent studies there are reports that CH4 can be produced and emitted from freshwater environments and oxygen-containing marine systems. It is therefore important to understand, and take into account factors related to the source, cycle and distribution of CH4 in environments with high anoxic and oxic variability, such as in the Jakarta Bay area which is interesting to study. In this study, the dissolved CH4 and air-sea water methane flux in the Jakarta Bay are measured to determine the contribution of CH4 to the atmosphere. The aims of this study are: (1) to identify dissolved CH4 concentrations in spatial distribution (2) to understand the sources of CH4 (3) to assess the releasing process of CH4 into the atmosphere. The measurement of dissolved methane utilizes a headspace equilibrium method. Based on dissolved CH4 concentration from each sampling locations, methane flux distribution is mapped for the coastal area of Jakarta. The met-ocean parameters such as salinity, currents, wind direction, pressure, temperature, and other factors which influence the distribution of methane flux were included in the analysis. This work still in progress and the abstract is hypothetical result of the research. Keywords: CH4, Jakarta Bay, Methane flux, Spatial distribution. Keywords: CH4, Jakarta Bay, Methane flux, Spatial distribution Share Link | Plain Format | Corresponding Author (Fadjar Hidajat)

103	Ocean-Atmosphere Dynamics	ABS-104
Evaluation of Subseasonal to Seasonal (S2S) Precipitation Forecast Performance from NMME-2 Model over Indonesia Dwina Nugraha (a), Muhammad Ridho Syahputra, S.Si., M.Si. (b), Dr. Muhammad Rais Abdillah, S.Si., M.Sc. (b) a) Department of Meteorology, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung, 40132, Indonesia b) Atmospheric Sciences Research Group, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung, 40132, Indonesia Abstract Subseasonal to Seasonal (S2S) precipitation forecast as a bridge for the gap between weather and seasonal forecast, can be utilized as supporting information for decision-making related to hydrometeorological disaster mitigation activities in Indonesia. However, uncertainty in global models caused forecast performance can be different across regions and time periods. Therefore, it is important to evaluate forecast performance before utilizing the prediction result. In this study, performance of probabilistic precipitation forecast from Multi-model Ensemble (MME) of three models in The North American Multi-Model Ensemble phase 2 (NMME-2) project was evaluated using evaluation metrics Continuous Ranked Probability Score (CRPS) and reliability diagram. The evaluation was conducted during the Boreal Summer (May-October) and Boreal Winter (November-April) periods, as well as during the active period of subseasonal climate variability phenomenon Madden-Julian Oscillation (MJO). The results show, S2S precipitation forecast from MME of three models in NMME-2 project are sufficiently accurate and reliable during the Boreal Summer period for Central Sumatra, Southern Sumatra, Southern Kalimantan, Java, Southern Sulawesi, and Southern Papua regions, with a range of CRPS values between 4-16 mm/7 days and a ^perfect^ reliability category. There is no significant difference in the performance of S2S precipitation forecast between the active and inactive events of the Madden-Julian Oscillation (MJO). The difference in CRPS values between these two periods is only around 0.8-1.2 mm/7 days, and there is no difference in reliability categories across Indonesia as a whole, nor significant spatial pattern differences. Keywords: Forecast performance, Precipitation, Subseasonal to Seasonal (S2S), NMME-2. Share Link | Plain Format | Corresponding Author (Dwina Nugraha)

104	Ocean-Atmosphere Dynamics	ABS-110
The Atmospheric and Oceanic Processes on Thermal Front Variability over the Java Sea Rahaden Bagas Hatmaja (a*), Rangga Amrullah (b), Shinta Ayu Kusumaningrum (b), and M. Restu Putra Sugianto (b) a) Research Center for Climate and Atmosphere, National Research and Innovation Agency (BRIN), Bandung, Indonesia * rahadenbagas[at]gmail.com b) Marine Science Department, Faculty of Fisheries and Marine Science, Padjajaran University, Sumedang, Indonesia Abstract The Java Sea is influenced by various atmospheric and oceanographic factors such as monsoon winds and the inflow of water from adjacent seas, thus lead to the formation of thermal fronts. In this research, the atmospheric process over the thermal front was estimated by using sea surface temperature (SST) gradient and crosswind-SST gradient calculation based on the GLORYS12V1 monthly SST data from Copernicus Marine Service (CMEMS) and the ERA5 monthly surface wind data from European Centre for Medium-Range Weather Forecasts (ECMWF) for 27 years (from 1993 to 2019). Moreover, the oceanic process was determined from the volume transports of three major channels surrounding the Java Sea, which are Karimata Strait, Sunda Strait, and the eastern boundary of the Java Sea. Based on the annual variance analysis, there are four main thermal front areas, such as Northern Java Coast (NJC), Eastern Sumatra Coast (ESC), Western Borneo Coast (WBC), and Eastern Borneo Coast (EBC). The annual variation of the thermal front over the ESC, WBC, and ESC has two peaks in March and October, while the NJC thermal front area has three peaks in March, July, and November. This study results that the thermal front activities over the NJC, WBC, and EBC are significantly correlated to the wind stress curl over those areas, with coefficient correlation about 0.62, -0.92, and -0.73, respectively. In addition, the increase in thermal front activity over the NJC area is controlled by negative wind stress curl with no lag time, while over the WBC and EBC areas are controlled by positive wind stress curl with a lag time of 1 month (wind stress leads). On the other hand, the thermal front activity over the ESC area is closely related to southward volume transport from the Karimata Strait, with a correlation coefficient of -0.74 and a lag time of 2 months (volume transport leads). Keywords: thermal front- Java Sea- SST gradient- wind stress curl- volume transport Share Link | Plain Format | Corresponding Author (Rahaden Bagas Hatmaja)

105	Ocean-Atmosphere Dynamics	ABS-111
Tidal Flood Analysis Based on Tidal Conditions and Meteorological Parameters in Banjarmasin City P L Sabrina (a*), I Ardiansyah (b), R Fauzy (a) a) Meteorology Study Program, State College of Meteorology, Climatology, and Geophysics , South Tangerang, Banten *purwantilelly.work[at]gmail.com , purwantilelly.work[at]stmkg.ac.id b) The National Agency for Disaster Countermeasure, East Jakarta, Jakarta Abstract Banjarmasin City is the capital of South Kalimantan Province which has a high risk of hydro-meteorological disasters in the form of droughts and floods. The flood disaster in Banjarmasin City can be caused by high rainfall and many rivers. In addition, tidal floods influenced by tides and other atmospheric conditions, also occur in Banjarmasin. Based on previous studies, tidal flooding was also affected by the geographical conditions of the City of Banjarmasin, which is a swamp with the topography of 0.16 m below sea level. This study will analyze the influence of tides and atmospheric conditions on tidal flooding in Banjarmasin. The method used is descriptive quantitatively using Delft 3D modeling to view tidal elevation parameters and using observation data from the Meteorology, Climatology and Geophysics Agency (BMKG) to analyze meteorological parameters. The Delft 3D model was simulated using two cases, namely tidal floods in 2021 and 2022. Verification compares the tidal elevation pattern of the model results with Geospatial Information Agency (BIG) data. In addition, statistical verification was also carried out in this study to determine the model^s error rate on the observation data. Keywords: Tidal flood, tides, meteorological conditions, Delft 3D model Share Link | Plain Format | Corresponding Author (Purwanti Lelly Sabrina)

106	Ocean-Atmosphere Dynamics	ABS-121
THE IDENTIFICATION OF UPWELLING IN THE OCCURRENCE OF TROPICAL CYCLONE CHARLOTTE IN THE WATERS OF SOUTHERN JAVA (CASE STUDY: March 17-28, 2022) Muhammad Ridwan Prasetya, Avrionesti, Yosafat Donni Haryanto, Latifah Nurul Qomariyatuzzamzami Sekolah Tinggi Meteorologi Klimatologi dan Geofisika Abstract Tropical cyclones are one of the meteorological phenomena that can have negative impacts on humans. These impacts can include heavy rainfall leading to floods and even storm surges. However, tropical cyclones can also have positive effects as they can trigger upwelling. Upwelling affects the fisheries aspect because in areas where upwelling occurs, sea surface temperatures are lower, and nutrients (such as phosphate and nitrate) are lifted from deeper layers of the ocean, which can affect the growth of phytoplankton. The objective of this research is to identify and analyze the upwelling phenomenon in the waters south of Java Island during the occurrence of Tropical Cyclone Charlotte. The data used in this research includes the intensity and movement direction of Tropical Cyclone Charlotte from the zoom.earth website and sea surface temperature, chlorophyll-a, mixed layer depth (MLD), and sea level anomaly data from the E.U. Copernicus Marine Service Information (CMEMS)-Global Monitoring and Forecasting Center during the period of March 17 to 28, 2022. The results of this research indicate that upwelling was not identified during the period before or after the cyclone, as evidenced by sea surface temperatures between 28.5 to 29.5 degree Celcius, chlorophyll-a concentration of less than 0.15 mg/m^3, and a sea level rise of 0.1 m. Keywords: upwelling, tropical cyclone, sea surface temperature, chlorophyll-a, Share Link | Plain Format | Corresponding Author (MUHAMMAD RIDWAN PRASETYA)

107	Ocean-Atmosphere Dynamics	ABS-122
ANALYSIS OF UPWELLING PARAMETERS WHEN THE EL NINO SOUTHERN OSCILLATION (ENSO) OCCURED IN THE HALMAHERA SEA Liberatus Marthinus, Avrionesti, Yosafat Donni H, Latifah Nurul Q Sekolah Tinggi Meteorologi Klimatologi dan Geofisika Abstract Upwelling events that occur in the Halmahera Sea are influenced by the El Nino Southern Oscillation (ENSO). Upwelling that occurs can affect sea surface temperatures to be lower than normal conditions so that they can affect the potential of fishery resources in the region. The purpose of this study was to determine the conditions of sea surface temperature, chlorophyll-a content, salinity, and upwelling conditions when viewed from the parameters of chlorophyll-a content and sea surface temperature when El Nino was strong, El Nino was weak, La Nina was strong, and La Nina weak and in normal conditions in the Halmahera Sea region. The data used in this study include the Oceanic Nino Index, sea surface temperature, salinity, and chlorophyll-a content during the 2010-2019 period. Using a quantitative descriptive research type by filtering ENSO data to determine the period when ENSO occurred, then visualizing the data in each parameter and analyzing it. The results of this study show that upwelling is known to occur in the northern to western parts of the Halmahera Sea. When the El Nino phase is strong, the upwelling parameter changes, the sea surface temperature decreases to 27.1 degrees celcius and the chlorophyll-a content increases to 0.70 mg/m3 compared to the normal phase, and the upwelling intensity changes. Keywords: El Nino Southern Oscillation, upwelling, SST, chlorophyll-a, Salinity Share Link | Plain Format | Corresponding Author (Liberatus Marthinus)

108	Operational Oceanography	ABS-21
Tidal Harmonic Analysis and Prediction to Support Early Warning for Coastal Flooding Randi Firdaus (a*), Nurul Tazaroh (a), Oky Surendra (a), Eko Prasetyo (a), Riris Adriyanto (a) a) Center for Marine Meteorology, Indonesian Agency for Meteorology Climatology and Geophysics (BMKG) Jalan Angkasa 1, No.2, Jakarta 10610, Indonesia *randi.firdaus[at]bmkg.go.id Abstract Indonesian Maritime Continent (IMC) is the largest archipelago that vulnerable to climate change especially sea level rise. Some coastal area frequently experiences the coastal flooding affecting the activities and infrastructures in the coastal area. Thus, an accurate tide prediction in this region has a pivotal role in order to provide the early warning, mitigation, and adaptation to frequent coastal flooding. BMKG through the Center for Marine Meteorology that mandate to provide the tidal information has done some effort to provide an accurate tidal prediction information through developing the tidal information system call INATIS (Indonesian Tidal Information System). The tidal harmonic analysis (THA) using the least-square method was applied to sea level data from 49 Marine Automatic Weather System (MAWS) stations for the period 2020-2022 to generate tidal predictions for the period 2022-2023. Tidal accuracy was assessed based on Mean Absolute Error (MAE) and the Mean Absolute Percentage Error (MAPE). MAWS stations with prediction accuracy above 80% were visualized on the online platform using the open-source Looker Studio, accessible to the public at https://maritim.bmkg.go.id/tide. The tidal predictions verification showed an average prediction accuracy of 93.21% with MAE of 0.114 m. The high accuracy of INATIS demonstrates its potential as a reference for coastal flood early warning systems. Keywords: tidal prediction, tidal harmonic, coastal inundation, looker studio Share Link | Plain Format | Corresponding Author (Randi Firdaus)

109	Operational Oceanography	ABS-31
Characteristics of Internal Waves in the Bali Sea from Sentinel-1A Data and Ocean Modeling Anszel Lukman (a), Agus Saleh Atmadipoera (a*), Dwiyoga Nugroho (b), Gentio Harsono (c) a) Marine Science and Technology Department, IPB University, Bogor Regency 16680, West Java, Indonesia *atmadipoera_itk[at]apps.ipb.ac.id b) National Research and Innovation Agency, Central Jakarta 10340, DKI Jakarta, Indonesia c) Hydrography and Oceanography Centre of Indonesian Navy, North Jakarta 14430, DKI Jakarta, Indonesia Abstract Internal waves (IWs) that propagate into the Bali Sea are supposed to originate from the sill area in the southern part of the Lombok Strait. This study aims to investigate surface features and mechanism of IWs formation and propagation into the Bali Sea. The datasets are acquired from the Sentinel-1A imageries and CROCO simulation. The results showed that solitary wave packets are spread over two areas: near Lombok Strait as generating area, and in the western and northern parts of the Bali Sea as propagating area. The length of IWs crests increased as they moved into the propagation area. The model showed that mixed semidiurnal tidal currents near the sill flow northward (southward) alternately during the flood (ebb) tidal period, resulting in the pycnocline deepening down to ~400 m near the northern sill area during the flood tide. Furthermore, the model demonstrated an alternating upward and downward movement of vertical currents components, associated with propagation of IWs^ crests and troughs along IWs pathway. Keywords: Bali Sea- Lombok Strait- internal waves- sill- Sentinel-1A imagery- CROCO model- tidal current Share Link | Plain Format | Corresponding Author (Anszel Lukman)

110	Operational Oceanography	ABS-64
WaveWatch III Model Verification using In Situ Buoy Observations in Karimunjawa Island Mohamad Husein Nurrahmat (a*), Roni Kurniawan (a), Erwin Eka Syahputra Makmur (a), Muhammad Najib Habibie (a), Thahir Daniel F Hutapea (a), Muhammad Rifki Taufik (a), Wido Hanggoro (a), Jaka Anugrah Ivanda Paski (a), Fatkhuroyan (a), Welly Fitria (a), Sri Novianti (a), Rezky Yunita (a), Rahayu Sapta Sri Sudewi (a), Vestiana Aza (a) a) Indonesian Agency for Meteorology, Climatology, and Geophysics Jalan Angkasa I No. 2, Jakarta Pusat, Indonesia *husein.nurrahmat[at]bmkg.go.id Abstract The accurate prediction of ocean waves is crucial for various coastal and marine applications. In this paper, we focus on verifying the performance of the WaveWatch III (WW3) numerical wave model in simulating wave conditions using in situ buoy observations. The survey has been conducted to capture a comprehensive dataset of Acoustic Doppler Current Profiler (ADCP) measurements for one month period in the Karimunjawa Island area. The study area in this paper is determined in two areas, shallow and deep waters. To assess the WW3 model^s performance, a set of statistical metrics is conducted, including root mean square error (RMSE), bias, and correlation coefficients. The data obtained from the model simulations are compared against the ADCP measurements to determine the overall model skill and identify potential discrepancies. The results of this verification contribute to our understanding of the WW3 model^s suitability for predicting wave conditions in Karimunjawa Island and provide valuable insights into local wave behavior in shallow and deep waters to develop more reliable and efficient wave prediction systems for coastal management and marine operations. Keywords: ADCP, Wavewatch III, Wave Prediction, Verification, Buoy Observation Share Link | Plain Format | Corresponding Author (Mohamad Husein Nurrahmat)

111	Operational Oceanography	ABS-96
Ocean parameter and hydrographic measurement around Cirebon port channel M R Badriana (1*), A A Nur (1), A I Hidayatullah (1), U Abdurrahman (1), L I Bernawis (3), C K Jeon (1,2), I M Radjawane (1,3), H S Park (1,2) 1) Korea-Indonesia Marine Technology Cooperation Research Center (MTCRC), Cirebon Center, Indonesia 2) Korea Institute of Ocean Science and Technology, Busan, Korea 3) Faculty of Earth Science and Technology, Bandung Institute of Technology, Bandung, Indonesia Abstract Cirebon port is one of the largest port in West Java province which plays a major role in supporting the surrounding economy and becoming the alternatives of the biggest port in Java. Numerous loading and unloading activities are recorded with coal as one of the commodities. Sedimentation and water quality is a common issue facing any port. To assess the recent condition of the port, an oceanographic parameter and hydrography survey is one approach. A field survey in the Cirebon port, particularly around the channel and outside part was carried out. The bathymetry result at the channel varied within 0 - 8 m depth. The mixed semidiurnal type in this area has a tidal range around 1.1 m. Sea current inside the port has low speed within 0-3 cm/s meanwhile outside of the port can reach 0.18 cm/s. Through the weathering system, the average temperature is 26.3 C, average wind speed of 2.5 m/s dominantly blowing from northeast, relative humidity around 88.6%, and rain rate also low. In the study, the sea condition of temperature, salinity, pH, turbidity, and DO is 28.4 - 29.86 C, 29.6 - 30.2 PSU, 7.8 - 8.3, 2.1 - 31 FTU, and 3.52 - 4.87 respectively. Based on the conformity of standard water quality, the condition for the port is within threshold for several parameters. Keywords: water quality, hydrography, channel port Share Link | Plain Format | Corresponding Author (Mochamad Riam Badriana)

112	Operational Oceanography	ABS-105
A closer look of Inner Indonesian Seas through float profilers deployment S Prasetyo, S Adiprabowo, M A Rahman, M F Geonova, F Alfahmi, A Ramdhani, E Prasetyo Indonesian Agency for Meteorology Climatology and Geophysics Abstract The marine weather information demand increases alongside the marine activities around Indonesian waters. Additionally, ocean observation supports the marine weather forecast operation by assimilating, validating, and improving data accuracy. Indonesia^s weather authority (BMKG) initiated the float profilers deployments to support the marine weather forecast operation through MMS - I (Maritime Meteorological Strengthening) Program. During the 2022 to 2024 period, this program deploys 48 floats around Indonesia^s prime and strategic waters, i.e., Natuna Sea, Karimata Strait, Java Sea, Makassar Strait, Flores Sea, Banda Sea, and the other future deployment spots. The ongoing deployments provide numerous ocean data. The visualized data provides a comprehensive view of the seasonal ocean dynamics in Indonesia. These dynamics are influenced by various factors, primarily the monsoon patterns and other natural forces. We gather crucial information about the ocean^s stratification and deep profile, including temperature and salinity. Furthermore, the continuous deployments of these profilers offer valuable insights into how the ocean^s behavior changes in response to the monsoon activity, particularly in regions such as the Natuna Sea, Karimata Strait, and the Java Sea. Further investigation and an extended data period are necessary to gain long-term variability of ocean dynamics in order to understand our changing ocean. Keywords: operational oceanography, marine meteorology, ocean dynamics Share Link | Plain Format | Corresponding Author (Suwignyo Prasetyo)

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