Hybrid Coordinate Ocean Model Research Articles

An Approach to Empirical Mapping of Incoherent Internal Tides With Altimetry Data

AbstractMuch of the internal tide (IT) is coherent with tidal forcing, but interactions with time‐varying ocean flows result in an incoherent component of IT (IIT), which will complicate interpretation of data from the upcoming Surface Water Ocean Topography (SWOT) mission. Here, we demonstrate a simple scheme for estimation of these IIT. We use a short‐time harmonic analysis of outputs of a wind‐ and tidally forced ocean model to generate an ensemble of IT variations in an ocean patch. Principal Components Analysis is used to define the dominant spatial patterns, and combined with sinusoidal time variations at tidal frequencies to define spatio‐temporal basis functions that are used to fit sparse altimetry data available in short time windows. The scheme is illustrated using a 1‐yr Hybrid Coordinate Ocean Model (HYCOM) run off the Amazon Shelf. Tests with synthetic (SWOT) and real (nadir altimetry) data demonstrate that a significant fraction of IIT can be recovered with this procedure.

Turnover Time of the East Sea (Sea of Japan) Meridional Overturning Circulation

The East Sea (ES; Sea of Japan) meridional overturning circulation (MOC) serves as a crucial mechanism for the transportation of dissolved, colloidal, and suspended particulate matters, including pollutants, on the surface to deep waters via thermohaline circulation. Therefore, understanding the structure of the ES MOC is critical for characterizing its temporal and spatial distribution. Numerous studies have estimated these parameters indirectly using chemical tracers, severely limiting the accuracy of the results. In this study, we provide a method for directly estimating the turnover times of the ES MOC using the stream functions calculated from HYbrid Coordinate Ocean Model (HYCOM) reanalysis data by averaging the flow pattern in the meridional 2-D plane. Because the flow pattern is not consistent but various over time, three cases of stream function fields were computed over a 20-year period. The turnover time was estimated by calculating the time required for water particles to circulate along the streamlines. In the cases of multiple (two or three) convection cells, we considered all possible scenarios of the exchange of water particles between adjacent cells, so that they circulated over those cells until finally returning to the original position and completing the journey on the ES MOC. Three different cell cases were tested, and each case had different water particle exchange scenarios. The resulting turnover times were 17.91–58.59 years, 26.41–37.28 years, and 8.68–45.44 years for the mean, deep, and shallow convection cases, respectively. The maximum turnover time, namely 58.59 years, was obtained when circulating the water particle over all three cells, and it was approximately half of that estimated by the chemical tracers in previous studies (∼100 years). This underestimation arose because the streamlines and water particle movement were not calculated in the shallow (<300 m) and deep areas (>3,000 m) in this study. Regardless, the results of this study provide insight into the ES MOC dynamics and indicate that the traditional chemical turnover time represents only one of the various turnover scenarios that could exist in the ES.

Ocean Current-Aided Localization and Navigation for Underwater Gliders With Information Matching Algorithm

The underwater glider (UG) is a new type of long-endurance marine vehicle that is currently widely used in marine environment surveillance. However, the limited capability of underwater communication and the uncertainty of the marine environment leads to a large deviation between the dead-reckoned trajectory and the real trajectory of UG. Therefore, a localization and navigation method based on ocean current data is proposed in this study. Firstly, the working principle and configuration of UG are illustrated, and the dynamic model is also analyzed. Then, the depth-averaged current is derived with motion parameters of UG, and the ocean current data from the Hybrid Coordinate Ocean Model is also introduced and processed. Meanwhile, to make an accurate localization, the DAC is stratified according to the layer weight extracted from the processed ocean current model to obtain layered DAC (LDAC). Subsequently, because the sample intervals of sensors are asynchronous with LDAC, a new matching algorithm based on sample time difference is presented to match the information of sensors and LDAC. Furthermore, the matched data is applied to localization for accurate dead reckoning. Finally, based on the data collected from two experiments, the LDAC-aided localization method proposed in this paper is compared with other benchmark positioning methods, including dynamic model-aided localization, sea current-aided localization, and acoustic beacon-aided localization methods. The results indicate that the proposed new method achieves better localization performance than other benchmark methods. In addition, the proposed method could be applied to other autonomous vehicles with communication constraints.

State Estimates and Forecasts of the Eddy Field in the Subtropical Countercurrent in the Northern Philippine Sea

AbstractA strongly nonlinear eddy field is present in and around the subtropical countercurrent in the northern Philippine Sea (NPS). A regional implementation of the Massachusetts Institute of Technology General Circulation Model–Estimating the Circulation and Climate of the Ocean four-dimensional variational assimilation (MITgcm-ECCO 4DVAR) system is found to be able to produce a series of 2-month-long dynamically consistent optimized state estimates between April 2010 and April 2011 for the eddy-rich NPS region. The assimilation provides a stringent dynamical test of the model, showing that a free run of the model forced using adjusted controls remains consistent with the observations for 2 months. The 4DVAR iterative optimization reduced the total cost function for the observations and controls by 40%–50% from the reference solution, initialized using the Hybrid Coordinate Ocean Model 1/12° global daily analysis, achieving residuals approximately equal to the assumed uncertainties for the assimilated observations. The state estimates are assessed by comparing with assimilated and withheld observations and also by comparing 1-month model forecasts with future data. The state estimates and forecasts were more skillful than model persistence and the reference solutions. Finally, the continuous state estimates were used to detect and track the eddies, analyze their structure, and quantify their vertically integrated meridional heat and salt transports.

Analysis of Abundance and Origin Possibility of Planktonic Foraminifera in Sulawesi Sea

Foraminifera is very diverse and adaptive, both in its morphology and biology. It is a potential bioindicator to understand the ecological and physical conditions of the ancient and modern waters based on their distribution. It has been well confirmed that the abundance of foraminifera (as a fossil) in sediment can reflect the ocean conditions above (mixed layer to upper ocean) where it was deposited. Planktonic foraminifera however can be considered as passive particles, their movement is carried by ocean currents. In consequence, the foraminifera abundance may represent more wider ocean condition according to the ocean current pattern. This study aims to examine the role of ocean currents in the distribution of foraminifera in the Sulawesi Sea. Ten gravity core sediment samples from 73-3009 m water depth were retrieved by RV Geomarin III from the Marine Geological Institute, Indonesia. We conducted quantitative analysis, including calculation of abundance and cluster analysis. Two decades (1992-2012) of ocean current simulated data from the Hybrid Coordinate Ocean Model (HYCOM) is used in this analysis, extending from 115°E-140°E and 8°N-2°S. The result indicates that planktonic foraminifera is abundant in the Sulawesi Sea by 86.3%. There were several predominant planktonic species such as Globigerinoides ruber (22.6%), Globigerina bulloides (15.3%), and Neoglobuquadrina dutertrei (10.1%). The ocean current above the sample location is constantly moving eastward as a part of the NECC. The average currents velocity shows that foraminifera in sample site S-03 with depth 2064 m may originated from up to 1035 kilometers away from its recent location.

Comparative performance of HWRF model coupled with POM and HYCOM for tropical cyclones over North Indian Ocean

The demonstration of air-sea interaction in the high-resolution numerical weather prediction (NWP) model is the necessary condition to predict the extreme event like tropical cyclone. It is already established that the coupled mesoscale models are capable of forecasting the track and intensity of tropical cyclones with reasonable skill over North Indian Ocean (NIO) basin and over other ocean basins as well. The Hurricane Weather Research and Forecasting (HWRF) model is consequently operational by India Meteorological Department (IMD) for the forecasting tropical cyclones like many other National Meteorological and Hydrological Services. Two different coupled versions of HWRF modeling systems with feature based Princeton Ocean Model (POM) and eddy-resolving Hybrid Coordinate Ocean Model (HYCOM) are employed for the real-time forecasting of tropical cyclones over NIO. In this study, the comparison of forecast skills between two coupled variants in predicting track and intensity for all eight cyclones during 2019 has been carried out. The results show that the track prediction of all cyclones by HWRF model coupled with HYCOM is comparatively better than that with POM. But the intensity prediction skills of both coupled models do not portray any obvious superiority for all forecast hours. The absolute intensity errors of HWRF model with POM coupling are large compared to HYCOM during initial phase up to 60 hours of forecast except for Vayu cyclone. But, the errors in intensity exhibited by POM are a bit smaller compared to HYCOM for longer lead period. However, the standard deviation is very large for both models and numbers of forecasts verified are also less. In case of two cyclones of 2020, the ability of coupled variant with HYCOM is superior to POM in forecasting the tracks of cyclones. Considering the skills of both the models for intensity prediction, it is clear that the use of coupled HCOM model for short-lived weaker storms is advantageous but the performance of the model is not consistently maintained with longer lead time for intense and long-lived cyclone. A brief assessment of surface fluxes and Sea Surface Temperature reveals that HYCOM portray more realistic ocean condition in turn surface fluxes compared to POM and therefore the coupled variant of HWRF with HYCOM is superior to the variant with POM while forecasting cyclones over deep Ocean.

Ocean Modeling in the Makassar Strait and Balikpapan Bay Using Online Nesting Method

Nur, A.A.; Suprijo, T.; Mandang, I.; Radjawane, I.M.; Park, H., and Khadami, F., 2021. Ocean modeling in the Makassar Strait and Balikpapan Bay using online nesting method. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 206–210. Coconut Creek (Florida), ISSN 0749-0208. This study had applied offline nesting method (one-way interaction) by using Regional Ocean Modeling System (ROMS) to simulate currents circulation in the Balikpapan Bay and showing good results with a high agreement between model output and observational measurement for water level data. It proves that even using the offline nesting method is the better option than increasing grid resolution on the entire model domain that will be demanding more computational cost, while the area of interest is a small-scale application. Therefore, this study aims to improve the model solution by using the online nesting method (two-way interaction) with a refinement ratio of 1:5 from the larger domain to a smaller domain. Three domains which include larger domain (L1) with spatial resolution 2.5 km that encompasses almost the entire Makassar Strait and acted as parent grid for the model. Coarser model of domain L2 with 500 m resolution becomes the buffer zone between the parent model (L1) and smaller domain (L3) in the Balikpapan Bay that has 100 m resolution. Initial and boundary conditions (IC/BC) for the L1 domain consisting of water levels, currents, temperature, and salinity were derived from the Hybrid Coordinate Ocean Model (HyCOM) re-analysis dataset. By using this method, there is only IC needed to be prepared for the other domain by interpolating IC data from the L1 domain and the BC would be provided directly from their larger domain during the simulation. Surface forcing for all domains extracted from the European Centre for Medium-Range Weather Forecast (ECMWF) ERA5 hourly dataset. Statistical methods such as Root Mean Square Error (RMSE) and model skill were used to validate model results for each model domain and found the improvement of the model solution when comparing observational data by model results for the larger and smaller domain at the same location, respectively.

Physics-informed neural networks for predicting ocean spatio-temporal fields

Simulations of the ocean environment are important for assessing acoustic variability due to large and small scale changes in the propagation medium. By incorporating the Internal Gravity Waves (IGWs) partial differential equation (PDE) in ocean models, such as the HYbrid Coordinate Ocean Model (HYCOM) system, it is possible to model the impact of tides on acoustic propagation. This requires HYCOM simulations of the ocean environment, which are computationally expensive, especially at the high vertical resolutions required to capture IGWs. In this work, we develop a machine-learning approach to predicting the effects of IGWs without incurring the computational cost of high-resolution numerical modeling. We apply a deep-learning approach in the form of a Physics Informed Neural Network (PINN) that incorporates the IGW PDE system to make predictions about oceanographic quantities of interest with internal tides at high vertical resolution. Training data comprise HYCOM 4D fields (time, depth, latitude, and longitude) both with (IGW-HYCOM) and without tides in the Pacific subtropical/equatorial region. The developed framework is able to map a relationship between lower-resolution HYCOM inputs to highly resolved ocean fields that include internal tides.

Deep ocean sound speed profile estimation using matched autoproduct processing

Sound speed profile (SSP) estimation from acoustic measurements alone in ocean environments is often a highly undetermined problem. Many methods have been developed which match arrival times or acoustic pressure observations to estimate a reduced-order SSP described with shape functions or empirical orthogonal functions (EOFs). These EOFs are commonly derived from multiple in situ measurements. This presentation describes an alternative method that matches autoproduct fields to invert for deep ocean SSPs without knowledge of the source waveform. The inverted SSPs are parameterized with EOFs derived from synthetic SSPs extracted from HYCOM (hybrid coordinate ocean model). This method is developed and illustrated using simulated long-range deep-ocean propagation data for frequencies in the 100s of Hz. The technique is also assessed with measured propagation data from the PhilSea10 experiment. [Sponsored by ONR]

The impact of internal tides and gravity waves on key acoustic parameters and acoustic transmission loss near the Amazon shelf

Upper ocean variability depends on tides and wind forcing. The barotropic tide creates baroclinic internal tides and internal gravity waves (IGWs) that can propagate long distances and dissipate, impacting mixed layer and thermocline depths, vertical thermal gradients, and mixing. In the last decade, there has been an effort to include tidal motions in global HYCOM (HYbrid Coordinate Ocean Model). Here, we look at the impacts of tidally driven motions on acoustic propagation along the Amazon shelf by comparing acoustic transmission loss and key acoustic parameters in 1/25 deg Global HYCOM model runs with and without tides. Acoustic runs were performed at mid-frequencies using Bellhop3D at depths above and below the sonic-layer depth (SLD). Key acoustic parameters assessed include the SLD and vertical sound-speed gradients. Although the impacts of the internal waves and tides on acoustics are intermingled with the effects of other stochastic ocean processes (e.g., mesoscale eddies, fronts, and atmospheric forcing), timeseries analysis indicates that there is acoustic sensitivity to tidally forced variability. These ocean-acoustic results can be used for future development of machine learning algorithms to model coupled oceanographic and acoustical processes.

Intraseasonal variability of the Indonesian throughflow associated with the Madden-Julian Oscillation

Intraseasonal variability (20–90 days) of the Indonesian Throughflow (ITF), which is primarily forced by the Madden-Julian Oscillation (MJO), is investigated using a high-resolution global ocean reanalysis and satellite altimeter data. Previous studies show that during the MJO active phase, downwelling Kelvin waves generated in the central equatorial Indian Ocean propagate along the coast of Sumatra and Java islands, affecting the ITF transport at exit passages in the Indonesian Seas and Makassar Strait. However, the intraseasonal variation of the ITF transport through these straits over the MJO life cycle, especially during the suppressed phase, has not been quantified. To quantify the ITF transport associated with the MJO, composites of ITF transport through major straits in the Indonesian Seas are constructed using a 0.08° global HYbrid Coordinate Ocean Model (HYCOM) reanalysis. A prominent reduction of ITF transport through major straits is found during the MJO active phase, and a transport enhancement comparable to the reduction is evident during the suppressed phase. As a result, the net effect of the MJO on the mean ITF transport is very small due to the cancellation of the enhancement and reduction. The magnitude of the MJO-associated ITF transport variation through all ITF exit passages is about 6 Sv, which is about 50% of the total transport. While the propagation of coastal Kelvin waves during the MJO active phase and their impact on ITF transport is clearly evident in the composite, such Kelvin wave influence on ITF transport is not clearly detected during the suppressed phase. This suggests that anomalous winds over the Maritime Continent (MC) area are mostly responsible for the ITF variation during the suppressed phase in many MJO events. Yet, during some MJO events, remotely-forced upwelling Kelvin waves and their significant impact on the ITF transport are evident during the MJO suppressed phase.

Generalized Kalman Filter and Ensemble Optimal Interpolation, Their Comparison and Application to the Hybrid Coordinate Ocean Model

In this paper, we consider a recently developed data assimilation method, the Generalized Kalman Filter (GKF), which is a generalization of the widely-used Ensemble Optimal Interpolation (EnOI) method. Both methods are applied for modeling the Atlantic Ocean circulation using the known Hybrid Coordinate Ocean Model. The along-track altimetry data taken from the Archiving, Validating and Interpolating Satellite Oceanography Data (AVISO) were used for data assimilation and other data from independent archives of observations; particularly, the temperature and salinity data from the Pilot Research Array in the Tropical Atlantic were used for independent comparison. Several numerical experiments were performed with their results discussed and analyzed. It is shown that values of the ocean state variables obtained in the calculations using the GKF method are closer to the observations in terms of standard metrics in comparison with the calculations using the standard data assimilation method EnOI. Furthermore, the GKF method requires less computational effort compared to the EnOI method.

Generation mechanism of the counter-wind South China Sea Warm Current in winter

A 22-year (1994–2015) HYbrid Coordinate Ocean Model (HYCOM) global reanalysis is used to study the generation mechanism of the counter-wind characteristic of the South China Sea Warm Current (SCSWC) in winter seasons. Our analysis clearly demonstrates that the counter-wind SCSWC in winter is driven by wind relaxation. An Extended Empirical Orthogonal Function (EEOF) analysis of the hourly Sea Surface Height (SSH) and wind stresses reveals that the most dominant SSH mode is an Ekman mode. When the wind relaxes, the Ekman transport anomaly is offshore and generates a favorable cross-shore SSH slope for the northeastward surface currents over the continental shelf mainly by geostrophic balance. The alongshore pressure gradient force also increases when the wind relaxes, and dominates the weak wind stresses to push the alongshore water northeastwards. We also identify the region south of Taiwan Strait as the origin of the SCSWC, instead of the Hainan Island or Gulf of Tonkin, Vietnam due to the dominant Ekman dynamics.

Simulated zonal current characteristics in the southeastern tropical Indian Ocean (SETIO)

Abstract. Detailed ocean currents in the southeastern tropical Indian Ocean adjacent to southern Sumatran and Javan coasts have not been fully explained because of limited observations. In this study, zonal current characteristics in the region have been studied using simulation results of a 1/8∘ global hybrid coordinate ocean model from 1950 to 2013. The simulated zonal currents across three meridional sections were then investigated using an empirical orthogonal function (EOF), where the first three modes account for 75 %–98 % of the total variance. The first temporal mode of EOF is then investigated using ensemble empirical mode decomposition (EEMD) to distinguish the signals. This study has revealed distinctive features of currents in the South Java Current (SJC) region, the Indonesian Throughflow (ITF)–South Equatorial Current (SEC) region, and the transition zone between these regions. The vertical structures of zonal currents in southern Java and offshore Sumatra are characterized by a one-layer flow. Conversely, a two-layer flow is observed in the nearshore and transition regions of Sumatra. Current variation in the SJC region has peak energies that are sequentially dominated by semiannual, intraseasonal, and annual timescales. Meanwhile, the transition zone is characterized by semiannual and intraseasonal periods with pronounced interannual variations. In contrast, interannual variability associated with El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) modulates the prominent intraseasonal variability of current in the ITF–SEC region. ENSO has the strongest influence at the outflow ITF, while the IOD's strongest influence is in southwestern Sumatra, with the ENSO (IOD) leading the current by 4 months (1 month). Moreover, the contributions (largest to smallest) of each EEMD mode at the nearshore of Java and offshore Sumatra are intraseasonal, semiannual, annual, interannual, and long-term fluctuations. The contribution of long-term variation (19.2 %) in the far offshore eastern Indian Ocean is larger than the interannual (16.3 %) and annual (14.7 %) variations. Future studies should be conducted to investigate this long-term variation.

OCEANIC DISPERSAL MODEL OF GREEN TURTLE HATCHLINGS IN THE SOUTH CHINA SEA

High-resolution ocean circulation models have increased our understanding of the movement and distribution of worldwide ocean currents, which were previously unknown and difficult to study. The metabolic expenditure data obtained through open-flow respirometric analysis was put into an energy budget context by comparing it to their available reserved energy in the body upon entering the swimming life phase. We modeled the dispersal range of green turtle hatchling from Chagar Hutang in various monsoon season using the particle-tracking program Ichthyop v3.2 and ocean surface current output from HYCOM (Hybrid Coordinate Ocean Model). The prediction distribution suggests that ocean current variability determines their movements into different dispersal areas. The simulated hatchlings are distributed north into the Gulf of Thailand during the Southwest monsoon, while during the Northeast monsoon, the simulated hatchlings travel south into the Java Sea. By quantifying hatchlings potential energy, they can swim a distance of 116 km and can last up to 7 days. Green turtle hatchlings from Chagar Hutang reached offshore water of Kelantan State and Terengganu waters near Tenggol Island on Day 7. These findings highlight areas of high priority for conservation, as habitat crucial for an endangered sea turtle species during a critical period of early development.

Dispersal modeling of octopoda paralarvae in the Gulf of Mexico

AbstractThe dynamics and population structure of octopus species in the Gulf of Mexico (GoM) can be studied by analyzing dispersal paralarvae mechanisms. Accordingly, this study focused on understanding octopus paralarval dispersal using numerical modeling. A Lagrangian approach was implemented using the transport model ICHTHYOP and surface currents from a GoM simulation of the HYbrid Coordinate Ocean Model (HYCOM). We modeled the dispersal of four octopus species from the GoM (Octopus “vulgaris”, Octopus insularis, Macrotritopus defilippi, and Amphioctopus burryi), considering two regions as the source of larvae in the southern GoM, namely the Yucatan shelf and the Veracruz coastal waters. Additionally, an environmental suitability analysis was incorporated using the maximum entropy (MaxEnt) model to establish potential settlement areas under the influence of the water masses’ thermal conditions. The simulation results supported the hypothesis that the abundances recorded in the GoM were influenced by the fertility (egg‐laying) of each species, surface water circulation (the Loop Current, eddies, and wind), and sea surface temperature. Greater dispersal was obtained throughout the GoM for Yucatan species O. “vulgaris”, registering the highest settlement rates. In contrast, in Veracruz, O. insularis dispersed and settled only in the western portion of the GoM. The relevance of the ecological descriptors proposed to influence the dispersal and abundance of octopods throughout the GoM's coastal waters are discussed.

Trace metal distributions and fluxes in the Taiwan Strait

The Taiwan Strait plays an important role as a corridor for the transport of water and chemicals between the South China Sea and the East China Sea, two of the largest marginal seas in the world, while receiving terrestrial material from land masses on both sides. In this study, we report on trace metal results in multiple cross-Strait transects during surveys of trace metal distributions and fluxes that reached from the northern South China Sea to the southern East China Sea. Plumes of elevated trace metal concentrations off the mainland China coast and off the northwest coast of Taiwan were documented to reach into the Taiwan Strait. Combining trace metal data with current velocity, obtained from HYbrid Coordinate Ocean Model (HYCOM), trace metal fluxes through multiple cross-sections in the Taiwan Strait were calculated. Seasonal variability in terrestrial source strength and current patterns in the Taiwan Strait dictated trace metal fluxes in different parts of the Strait. The northward fluxes were smaller during northeastern monsoon in the fall/winter because of the greater southward Chinese Coastal Current, which carried terrestrial trace metal sources in its water into the Taiwan Strait. Some trace metals had strong linear relationships with salinity within plume extensions, within a few tens of kilometers off a major river mouth. Results show that varying monsoon-induced water transports led to distinctively different trace metal distributions and fluxes at different times and through different transects across the Taiwan Strait.

The features of the coastal fronts in the Eastern Guangdong coastal waters during the downwelling-favorable wind period

A coastal front was detected in the eastern Guangdong (EGD) coastal waters during a downwelling-favorable wind period by using the diffuse attenuation coefficient at 490 nm (Kd(490)). Long-term satellite data, meteorological data and hydrographic data collected from 2003 to 2017 were jointly utilized to analyze the environmental factors affecting coastal fronts. The intensities of the coastal fronts were found to be associated with the downwelling intensity. The monthly mean Kd(490) anomalies in shallow coastal waters less than 25 m deep along the EGD coast and the monthly mean Ekman pumping velocities retrieved by the ERA5 dataset were negatively correlated, with a Pearson correlation of − 0.71. The fronts started in October, became weaker and gradually disappeared after January, extending southwestward from the southeastern coast of Guangdong Province to the Wanshan Archipelago in the South China Sea (SCS). The cross-frontal differences in the mean Kd(490) values could reach 3.7 m−1. Noticeable peaks were found in the meridional distribution of the mean Kd(490) values at 22.5°N and 22.2°N and in the zonal distribution of the mean Kd(490) values at 114.7°E and 114.4°E. The peaks tended to narrow as the latitude increased. The average coastal surface currents obtained from the global Hybrid Coordinate Ocean Model (HYCOM) showed that waters with high nutrient and sediment contents in the Fujian and Zhejiang coastal areas in the southern part of the East China Sea could flow into the SCS. The directions and lengths of the fronts were found to be associated with the flow advection.

Oil spill trajectory prediction assessment using multi model ocean currents - case study of MT Dawn Oil spill 2017

Abstract 684276 An assessment was carried out to judge the performance of the modeled ocean currents in oil spill trajectory prediction. Ocean circulation is the key factor in determining the drift pattern of the spilled marine oil pollutant. General National Oceanic and Atmospheric Administration Operational Modeling Environment (GNOME), an oil spill trajectory model, in diagnostic mode was set for simulating drift pattern of Heavy Fuel Oil (HFO). On 28 January 2017, 0345 hrs, Indian Standard Time (IST), approximately 196.4 MT of HFO was spilled due to vessel collision. The oil spill model was set and run during 28-Jan-2017 to 05-Feb-2017 with 196 tons of HFO. Wind velocity fields were obtained from European Centre for Medium-Range Weather Forecasts (ECMWF). The modeled ocean currents were obtained from High resolution Operational Ocean Forecasting and reanalysis System (HOOFS) with two model set ups such as Indian ocean (IO) and Bay Of Bengal (BOB). Ocean current pattern were also obtained from Hybrid Co-ordinate Ocean Model (HYCOM) and Global Ocean Data Assimilation System (GODAS) based Modular Ocean Model (GM4P1). The oil drift patterns were simulated individually for the spillage due to MT Dawn vessel, by forcing GNOME with the above said wind and ocean currents. Radar data obtained for 29-Jan-2017, from Sentinel -1A was processed for detecting oil slicks. The respective drift patterns obtained were compared individually with the oil slick signatures of Sentinel -1A on 29-Jan-2017. It was found that the drift pattern obtained while using the ocean currents of HOOFS_BOB was in better agreement with that of the observed slicks. Unlike other oil drift patterns, offshore spread of the slicks are well captured while using the ocean currents of HOOFS_BOB. This paper illustrates the method of oil spill trajectory prediction using various ocean currents and validating the simulated drift with the ground truth. It also emphasize the need of using various modeled ocean currents in assessing the performance of oil spill trajectory model.

Sensitivity Analysis of OTEC-CC-MX-1 kWe Plant Prototype

The Mexican Caribbean Sea has potential zones for Ocean Thermal Energy Conversion (OTEC) implementation. Universidad del Caribe and Instituto de Ciencias del Mar y Limnologia, with the support of the Mexican Centre of Innovation in Ocean Energy, designed and constructed a prototype OTEC plant (OTEC-CC-MX-1 kWe), which is the first initiative in Mexico for exploitation of this type of renewable energy. This paper presents a sensitivity analysis whose objective was to know, before carrying out the experimental tests, the behavior of OTEC-CC-MX-1 kWe regarding temperature differences, as well as the non-possible operating conditions, which allows us to assess possible modifications in the prototype installation. An algorithm was developed to obtain the inlet and outlet temperatures of the water and working fluid in the heat exchangers using the monthly surface and deep-water temperature data from the Hybrid Coordinate Ocean Model and Geographically Weighted Regression Temperature Model for the Mexican Caribbean Sea. With these temperatures, the following were analyzed: fluctuation of thermal efficiency, mass flows of R-152a and water and power production. By analyzing the results, we verified maximum and minimum mass flows of water and R-152a to produce 1 kWe during a typical year in the Mexican Caribbean Sea and the conditions when the production of electricity is not possible for OTEC-CC-MX-1 kWe.