Pub Date : 2024-11-22DOI: 10.1016/j.ocemod.2024.102464
Yuchen He , Amin Chabchoub
Rogue waves, which form on the ocean’s surface, can cause significant damage to marine installations and pose a serious threat to ship safety. Understanding the physical mechanisms behind extreme wave focusing is crucial for predicting their formation and mitigating their impact. Two intensively discussed wave amplification frameworks are the linear and nonlinear focusing mechanisms. These are also known as superposition principle and modulation instability, respectively. We report an experimental study investigating the formation mechanisms in a unidirectional representative JONSWAP-type sea state and show that the nonlinear focusing principle can be sub-categorized into either a localized amplitude or a so far less-studied phase-related frequency modulation, or both being at play. The frequency modulation-type mechanism occurs at a lower probability, as suggested from the distribution of more than 200 recorded extreme events, however, it cannot be underrated or disregarded.
{"title":"On long-crested ocean rogue waves originating from localized amplitude and frequency modulations","authors":"Yuchen He , Amin Chabchoub","doi":"10.1016/j.ocemod.2024.102464","DOIUrl":"10.1016/j.ocemod.2024.102464","url":null,"abstract":"<div><div>Rogue waves, which form on the ocean’s surface, can cause significant damage to marine installations and pose a serious threat to ship safety. Understanding the physical mechanisms behind extreme wave focusing is crucial for predicting their formation and mitigating their impact. Two intensively discussed wave amplification frameworks are the linear and nonlinear focusing mechanisms. These are also known as superposition principle and modulation instability, respectively. We report an experimental study investigating the formation mechanisms in a unidirectional representative JONSWAP-type sea state and show that the nonlinear focusing principle can be sub-categorized into either a localized amplitude or a so far less-studied phase-related frequency modulation, or both being at play. The frequency modulation-type mechanism occurs at a lower probability, as suggested from the distribution of more than 200 recorded extreme events, however, it cannot be underrated or disregarded.</div></div>","PeriodicalId":19457,"journal":{"name":"Ocean Modelling","volume":"193 ","pages":"Article 102464"},"PeriodicalIF":3.1,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142748207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-19DOI: 10.1016/j.ocemod.2024.102456
Sebastian Omar Correa Araya , Catalina Aguirre , Diego Becerra , Mauricio Molina , Pablo Vilchez , Sergio Bahamóndez
The Chilean Wave Atlas (AOC1), a reliable hindcast developed in 2017 for the academic and engineering community, diminished its usefulness due to the obsolescence of wind data provided by ERA-Interim reanalysis. This study presents the calibration and validation of a new wave hindcast forced using hourly winds data from ERA5 reanalysis. A total of 24 simulations were conducted: 15 using the semi-empirical ST4 parameterization and 9 using the observed-based ST6 parameterization, both implemented in WaveWatch III. Model results were compared with in-situ wave data from buoys along the Chilean coast. Generally, the ST4 physics package demonstrated superior performance with minimal variability in error statistical parameters between simulations. However, the observed-based ST6 parameterization produced the best results for simulating wave direction. By defining a multi-criteria performance score, the optimal model configuration was selected, and a new hindcast was generated for the period between 1979 and 2022. This hindcast includes hourly fields of significant wave height, mean and peak wave period, and mean and peak wave direction for the Pacific Ocean, as well as 72 locations with directional spectra. The upgraded Chilean Wave Atlas (AOC3) significantly improves the performance of AOC1 when compared with satellite-derived wave heights along the Chilean coast. Furthermore, the AOC3 data show good performance compared to other freely available hindcasts.
{"title":"Upgrade of the Chilean Wave Atlas database","authors":"Sebastian Omar Correa Araya , Catalina Aguirre , Diego Becerra , Mauricio Molina , Pablo Vilchez , Sergio Bahamóndez","doi":"10.1016/j.ocemod.2024.102456","DOIUrl":"10.1016/j.ocemod.2024.102456","url":null,"abstract":"<div><div>The Chilean Wave Atlas (AOC1), a reliable hindcast developed in 2017 for the academic and engineering community, diminished its usefulness due to the obsolescence of wind data provided by ERA-Interim reanalysis. This study presents the calibration and validation of a new wave hindcast forced using hourly winds data from ERA5 reanalysis. A total of 24 simulations were conducted: 15 using the semi-empirical ST4 parameterization and 9 using the observed-based ST6 parameterization, both implemented in WaveWatch III. Model results were compared with in-situ wave data from buoys along the Chilean coast. Generally, the ST4 physics package demonstrated superior performance with minimal variability in error statistical parameters between simulations. However, the observed-based ST6 parameterization produced the best results for simulating wave direction. By defining a multi-criteria performance score, the optimal model configuration was selected, and a new hindcast was generated for the period between 1979 and 2022. This hindcast includes hourly fields of significant wave height, mean and peak wave period, and mean and peak wave direction for the Pacific Ocean, as well as 72 locations with directional spectra. The upgraded Chilean Wave Atlas (AOC3) significantly improves the performance of AOC1 when compared with satellite-derived wave heights along the Chilean coast. Furthermore, the AOC3 data show good performance compared to other freely available hindcasts.</div></div>","PeriodicalId":19457,"journal":{"name":"Ocean Modelling","volume":"193 ","pages":"Article 102456"},"PeriodicalIF":3.1,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-16DOI: 10.1016/j.ocemod.2024.102463
A. Yavuzdoğan , E. Tanir Kayıkçı
Rising sea levels pose significant risks to coastal communities and ecosystems. Accurate modeling of sea level changes is crucial for effective environmental management and disaster mitigation. Machine learning methods are emerging as an important asset in improving sea level predictions and understanding the impacts of climate change. Especially, Long Short-Term Memory (LSTM) models have emerged as a powerful tool for sea level anomaly modeling, but there is an increasing need for more advanced models in this area. This study enhances existing methodologies by introducing a novel approach using an LSTM Auto-Encoder model, designed to compress input data into a lower-dimensional latent space before reconstructing it, thereby capturing complex temporal dependencies and anomalies effectively. We compared LSTM Auto-Encoder model performance with that of a Stacked LSTM network, which learns complex temporal patterns through multiple layers, and a traditional damped-persistence statistical model. Our results demonstrate that the LSTM Auto-Encoder model not only outperformed these models in predicting sea level anomalies across various lead times but also exhibited superior generalization capabilities across both satellite altimeter and in-situ data. These findings highlight the potential of the LSTM Auto-Encoder model as a powerful tool in coastal management and climate change studies, underscoring the critical role of advanced machine learning techniques in enhancing our predictive abilities and informing disaster preparedness strategies.
{"title":"Advancing sea level anomaly modeling in the black sea with LSTM Auto-Encoders: A novel approach","authors":"A. Yavuzdoğan , E. Tanir Kayıkçı","doi":"10.1016/j.ocemod.2024.102463","DOIUrl":"10.1016/j.ocemod.2024.102463","url":null,"abstract":"<div><div>Rising sea levels pose significant risks to coastal communities and ecosystems. Accurate modeling of sea level changes is crucial for effective environmental management and disaster mitigation. Machine learning methods are emerging as an important asset in improving sea level predictions and understanding the impacts of climate change. Especially, Long Short-Term Memory (LSTM) models have emerged as a powerful tool for sea level anomaly modeling, but there is an increasing need for more advanced models in this area. This study enhances existing methodologies by introducing a novel approach using an LSTM Auto-Encoder model, designed to compress input data into a lower-dimensional latent space before reconstructing it, thereby capturing complex temporal dependencies and anomalies effectively. We compared LSTM Auto-Encoder model performance with that of a Stacked LSTM network, which learns complex temporal patterns through multiple layers, and a traditional damped-persistence statistical model. Our results demonstrate that the LSTM Auto-Encoder model not only outperformed these models in predicting sea level anomalies across various lead times but also exhibited superior generalization capabilities across both satellite altimeter and in-situ data. These findings highlight the potential of the LSTM Auto-Encoder model as a powerful tool in coastal management and climate change studies, underscoring the critical role of advanced machine learning techniques in enhancing our predictive abilities and informing disaster preparedness strategies.</div></div>","PeriodicalId":19457,"journal":{"name":"Ocean Modelling","volume":"193 ","pages":"Article 102463"},"PeriodicalIF":3.1,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-15DOI: 10.1016/j.ocemod.2024.102462
Yongzhi Liu , Minjie Xu , Xianqing Lv
Ecological modeling is an important methodology for studying the spatio-temporal evolution of marine ecosystem. Given the significant role of model parameters as a major source of uncertainty in ecological models, we propose a novel approach by combining the Conditional Nonlinear Optimal Perturbation related to Parameters (CNOP-P) method with the adjoint assimilation method to enhance predictive accuracy. CNOP-P denotes the parameter perturbation that leads to the greatest deviation of the model's development from the reference state. In comparison to other sensitivity analysis methods, this combined approach proves to be more efficient. Considering the nonlinearity of the model structure, the maximum development of the model does not consistently align with the extreme parameter values within the confidence interval. Minor parameter errors can lead to substantial model development, significantly impacting the precision of ecological models. Notably, traditional sensitivity analysis methods such as one-at-a-time (OAT) sensitivity analysis and global sensitivity analysis (GSA) methods fail to capture this characteristic. On the other hand, the GSA methods incur substantial computational costs and tends to overestimate the sensitivity of the most sensitive parameters while underestimating the sensitivity of less sensitive parameters. The combined approach of CNOP-P and adjoint assimilation enables the assimilation of satellite data and the simultaneous optimization of model parameters alongside the CNOP-P calculations. This integration substantially improves both efficiency and precision of the ecological model, thereby improving predictive skill.
{"title":"Improving ecological modeling: Integrating CNOP-P and adjoint assimilation in a coupled ecological model","authors":"Yongzhi Liu , Minjie Xu , Xianqing Lv","doi":"10.1016/j.ocemod.2024.102462","DOIUrl":"10.1016/j.ocemod.2024.102462","url":null,"abstract":"<div><div>Ecological modeling is an important methodology for studying the spatio-temporal evolution of marine ecosystem. Given the significant role of model parameters as a major source of uncertainty in ecological models, we propose a novel approach by combining the Conditional Nonlinear Optimal Perturbation related to Parameters (CNOP-P) method with the adjoint assimilation method to enhance predictive accuracy. CNOP-P denotes the parameter perturbation that leads to the greatest deviation of the model's development from the reference state. In comparison to other sensitivity analysis methods, this combined approach proves to be more efficient. Considering the nonlinearity of the model structure, the maximum development of the model does not consistently align with the extreme parameter values within the confidence interval. Minor parameter errors can lead to substantial model development, significantly impacting the precision of ecological models. Notably, traditional sensitivity analysis methods such as one-at-a-time (OAT) sensitivity analysis and global sensitivity analysis (GSA) methods fail to capture this characteristic. On the other hand, the GSA methods incur substantial computational costs and tends to overestimate the sensitivity of the most sensitive parameters while underestimating the sensitivity of less sensitive parameters. The combined approach of CNOP-P and adjoint assimilation enables the assimilation of satellite data and the simultaneous optimization of model parameters alongside the CNOP-P calculations. This integration substantially improves both efficiency and precision of the ecological model, thereby improving predictive skill.</div></div>","PeriodicalId":19457,"journal":{"name":"Ocean Modelling","volume":"193 ","pages":"Article 102462"},"PeriodicalIF":3.1,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-14DOI: 10.1016/j.ocemod.2024.102465
Anna Maggiorano, Mark Baird, Clothilde Langlais, Mathieu Mongin, Jennifer Skerratt
Solar radiation propagating through the water column is scattered and absorbed by optically active constituents in the ocean, in particular phytoplankton, coloured-dissolved organic matter (CDOM), suspended inorganic particulate matter (SPIM) and detritus. These wavelength-dependent processes affect the vertical distribution of heating in the water column and its stratification. The continental shelf north-east of Australia, containing the Great Barrier Reef (GBR), is characterised by highly seasonal and intermittent freshwater inputs leading to large sediment and nutrient discharges that strongly impact the water optical properties. While this complex mixture of optically active constituents is known to affect water clarity and the euphotic zone depth in the river plumes, its impact on the ocean circulation and thermal balance is still unclear at the scale of the GBR. In this study, we use a hydrodynamic-optical-biogeochemical ocean model to investigate the feedback between heat absorption by phytoplankton, CDOM and suspended sediments and ocean dynamics in the GBR region. The results show that the attenuation of the vertical heat flux due to phytoplankton, CDOM and SPIM concentrations is stronger on the continental shelf and dominated by the absorption and scattering from suspended sediments. The presence of absorbing constituents in the water column drives a temperature increase at the surface and a decrease below the mixed layer with stronger stratification and greater heat losses to the atmosphere. Inshore, the ocean heat content increases by up to 1% due to optically active constituents. Offshore, absorption by optically active constituents near the surface is compensated by less absorption underneath the mixed layer resulting in a decrease in the ocean heat content of the top 500 m. We find that considering a spatially- and temporally-variable vertical attenuation of heat due to multiple optically-active components improves hydrodynamic model skill. This study highlights the importance of the impact of water clarity and its spatial variability on hydrodynamic processes.
{"title":"Impact of phytoplankton, CDOM, and suspended sediments on the vertical attenuation of light, changing heat content and circulation on a continental shelf: A modelling study of the Great Barrier Reef","authors":"Anna Maggiorano, Mark Baird, Clothilde Langlais, Mathieu Mongin, Jennifer Skerratt","doi":"10.1016/j.ocemod.2024.102465","DOIUrl":"10.1016/j.ocemod.2024.102465","url":null,"abstract":"<div><div>Solar radiation propagating through the water column is scattered and absorbed by optically active constituents in the ocean, in particular phytoplankton, coloured-dissolved organic matter (CDOM), suspended inorganic particulate matter (SPIM) and detritus. These wavelength-dependent processes affect the vertical distribution of heating in the water column and its stratification. The continental shelf north-east of Australia, containing the Great Barrier Reef (GBR), is characterised by highly seasonal and intermittent freshwater inputs leading to large sediment and nutrient discharges that strongly impact the water optical properties. While this complex mixture of optically active constituents is known to affect water clarity and the euphotic zone depth in the river plumes, its impact on the ocean circulation and thermal balance is still unclear at the scale of the GBR. In this study, we use a hydrodynamic-optical-biogeochemical ocean model to investigate the feedback between heat absorption by phytoplankton, CDOM and suspended sediments and ocean dynamics in the GBR region. The results show that the attenuation of the vertical heat flux due to phytoplankton, CDOM and SPIM concentrations is stronger on the continental shelf and dominated by the absorption and scattering from suspended sediments. The presence of absorbing constituents in the water column drives a temperature increase at the surface and a decrease below the mixed layer with stronger stratification and greater heat losses to the atmosphere. Inshore, the ocean heat content increases by up to 1% due to optically active constituents. Offshore, absorption by optically active constituents near the surface is compensated by less absorption underneath the mixed layer resulting in a decrease in the ocean heat content of the top 500 m. We find that considering a spatially- and temporally-variable vertical attenuation of heat due to multiple optically-active components improves hydrodynamic model skill. This study highlights the importance of the impact of water clarity and its spatial variability on hydrodynamic processes.</div></div>","PeriodicalId":19457,"journal":{"name":"Ocean Modelling","volume":"193 ","pages":"Article 102465"},"PeriodicalIF":3.1,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-13DOI: 10.1016/j.ocemod.2024.102458
H.M. Aravind , Tamay M. Özgökmen , Michael R. Allshouse
Lagrangian analyses of oceanic flows provide insight into the various transport pathways in the ocean. This analysis typically relies on a dense set of trajectories that can be computed using high-resolution velocity fields, which are often not available during field experiments. Instruments like drifters and floats are often employed to overcome the limitations imposed by satellite- and radar-based velocity fields, to understand the transport pathways in the ocean. However, the sparsity in available drifter-trajectory data proves prohibitive to obtaining a comprehensive map of the Lagrangian characteristics of the underlying flow. To circumvent these issues, we use Gaussian Process Regression (GPR) to obtain velocity fields from sparse drifter data to generate synthetic trajectories and subsequently estimate two Lagrangian metrics, FTLE and dilation rate. A detailed error analysis is performed for drifter clusters deployed within various dynamical regions in the analytic Bickley jet system. The uncertainties in velocity reconstruction obtained from the GPR method, averaged along particle trajectories, locate Lagrangian confidence regions that are applicable both to synthetic trajectories and the dilation rate field. A sensitivity analysis reveals the role played by factors such as the spatial sampling density and temporal resolution of the drifter data, as well as the effect of position uncertainty as a result of GPS inaccuracy. The method is then applied to the drifter data from the Lagrangian Submesoscale Experiment in 2016 to locate convergent filaments. The results present a marked improvement over direct estimation of area-averaged dilation rates using drifter clusters.
{"title":"Lagrangian analysis of submesoscale flows from sparse data using Gaussian Process Regression for field reconstruction","authors":"H.M. Aravind , Tamay M. Özgökmen , Michael R. Allshouse","doi":"10.1016/j.ocemod.2024.102458","DOIUrl":"10.1016/j.ocemod.2024.102458","url":null,"abstract":"<div><div>Lagrangian analyses of oceanic flows provide insight into the various transport pathways in the ocean. This analysis typically relies on a dense set of trajectories that can be computed using high-resolution velocity fields, which are often not available during field experiments. Instruments like drifters and floats are often employed to overcome the limitations imposed by satellite- and radar-based velocity fields, to understand the transport pathways in the ocean. However, the sparsity in available drifter-trajectory data proves prohibitive to obtaining a comprehensive map of the Lagrangian characteristics of the underlying flow. To circumvent these issues, we use Gaussian Process Regression (GPR) to obtain velocity fields from sparse drifter data to generate synthetic trajectories and subsequently estimate two Lagrangian metrics, FTLE and dilation rate. A detailed error analysis is performed for drifter clusters deployed within various dynamical regions in the analytic Bickley jet system. The uncertainties in velocity reconstruction obtained from the GPR method, averaged along particle trajectories, locate Lagrangian confidence regions that are applicable both to synthetic trajectories and the dilation rate field. A sensitivity analysis reveals the role played by factors such as the spatial sampling density and temporal resolution of the drifter data, as well as the effect of position uncertainty as a result of GPS inaccuracy. The method is then applied to the drifter data from the Lagrangian Submesoscale Experiment in 2016 to locate convergent filaments. The results present a marked improvement over direct estimation of area-averaged dilation rates using drifter clusters.</div></div>","PeriodicalId":19457,"journal":{"name":"Ocean Modelling","volume":"193 ","pages":"Article 102458"},"PeriodicalIF":3.1,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142748208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-12DOI: 10.1016/j.ocemod.2024.102459
Mikhail Lavrentiev , Andrey Marchuk , Konstantin Oblaukhov
This paper proposes the use of specialized hardware accelerator based on the Field Programmable Gates Array (FPGA) microchip to compute tsunami wave propagation to assess and manage risks of marine natural disasters, namely, tsunami waves caused by underwater earthquakes. After a sufficiently strong seismic event, many countries and research centres launch extensive computations to estimate the tsunami wave parameters in certain parts of the coast to determine if a declaration of a tsunami alarm is warranted. This requires high computating powers which leads to higher energy costs. The paper demonstrates how an FPGA-based special Calculator (architecture of which has been earlier proposed by the authors), installed on a Personal Computer (PC) could be used to calculate the propagation of a tsunami wave over the entire Pacific Ocean, from the subduction zone offshore Kamchatka Peninsula and Kuril Islands to the coast of Chile. Such calculations offer reliable results within a few minutes and make it possible to obtain the distribution of expected tsunami wave heights along the coast. If the obtained results indicate a danger to the population or possible destruction of infrastructure, it becomes paramount to carry out more detailed calculations to accurately estimate the wave parameters at specific locations along the coast where negative consequences are expected. This requires cluster and/or supercomputer systems, which consume significant energy and hence are expensive. In case the modelling results indicate small values of maximum wave heights at populated coastal areas, population of the near-shore regions can be immediately informed about low amplitude tsunami wave; more detailed studies are not needed. This hence leads to noticeable savings in energy consumption. The paper presents a calculation of the propagation of a tsunami wave across the Pacific Ocean on a personal computer using a FPGA-based hardware acceleration of a computer code execution.
{"title":"Low power computation of transoceanic wave propagation for tsunami hazard mitigation","authors":"Mikhail Lavrentiev , Andrey Marchuk , Konstantin Oblaukhov","doi":"10.1016/j.ocemod.2024.102459","DOIUrl":"10.1016/j.ocemod.2024.102459","url":null,"abstract":"<div><div>This paper proposes the use of specialized hardware accelerator based on the Field Programmable Gates Array (FPGA) microchip to compute tsunami wave propagation to assess and manage risks of marine natural disasters, namely, tsunami waves caused by underwater earthquakes. After a sufficiently strong seismic event, many countries and research centres launch extensive computations to estimate the tsunami wave parameters in certain parts of the coast to determine if a declaration of a tsunami alarm is warranted. This requires high computating powers which leads to higher energy costs. The paper demonstrates how an FPGA-based special Calculator (architecture of which has been earlier proposed by the authors), installed on a Personal Computer (PC) could be used to calculate the propagation of a tsunami wave over the entire Pacific Ocean, from the subduction zone offshore Kamchatka Peninsula and Kuril Islands to the coast of Chile. Such calculations offer reliable results within a few minutes and make it possible to obtain the distribution of expected tsunami wave heights along the coast. If the obtained results indicate a danger to the population or possible destruction of infrastructure, it becomes paramount to carry out more detailed calculations to accurately estimate the wave parameters at specific locations along the coast where negative consequences are expected. This requires cluster and/or supercomputer systems, which consume significant energy and hence are expensive. In case the modelling results indicate small values of maximum wave heights at populated coastal areas, population of the near-shore regions can be immediately informed about low amplitude tsunami wave; more detailed studies are not needed. This hence leads to noticeable savings in energy consumption. The paper presents a calculation of the propagation of a tsunami wave across the Pacific Ocean on a personal computer using a FPGA-based hardware acceleration of a computer code execution.</div></div>","PeriodicalId":19457,"journal":{"name":"Ocean Modelling","volume":"192 ","pages":"Article 102459"},"PeriodicalIF":3.1,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work examines the use of discrete variance decay of tracers to estimate locally in space and time the numerical mixing caused by different processes during a tracer transport step. Expressions for local discrete variance decay (DVD) rates are directly derived from discrete tracer equations without any assumptions on discrete fluxes of the second moment. They relate the DVD rates to the fluxes of the first moment through the faces of scalar control cell. Mixing associated with advective and diffusive fluxes is thus estimated. The new framework avoids the need for second-moment flux definition when solved directly on finite-volume cell faces but still invokes certain second-moment fluxes when the face DVD rates are partitioned to cells sharing the face. These implied discrete fluxes depend on the partitioning and are non-unique. For third- or higher-order advection schemes, the DVD rates are contaminated by dispersive errors intrinsic to the approach, introducing uncertainty to the locality of any estimates produced by it. Additional temporal averaging or coarse-graining is thus necessary. Through the application of this technique, numerical mixing is found to be correlated with the distribution of eddy kinetic energy. Numerical mixing induced by vertical advection is found to be relatively small and correlated with the distribution of buoyancy fluxes. The explored high-order schemes are found to demonstrate levels of spurious mixing which may locally exceed physical mixing.
这项研究利用示踪剂的离散方差衰减来估算示踪剂传输步骤中不同过程在空间和时间上造成的局部数值混合。局部离散方差衰减（DVD）率的表达式直接来自离散示踪剂方程，无需对第二时刻的离散通量做任何假设。它们将 DVD 率与通过标量控制单元面的第一时刻通量联系起来。这样就可以估算出与平流和扩散通量相关的混合情况。当直接求解有限体积单元面时，新框架避免了第二时刻通量定义的需要，但当面的 DVD 率被分割到共享面的单元时，仍会调用某些第二时刻通量。这些隐含的离散通量取决于分区，并且是非唯一的。对于三阶或更高阶的平流方案，DVD 率会受到该方法固有的分散误差的污染，从而为其产生的任何估计值的定位带来不确定性。因此，有必要进行额外的时间平均或粗粒化。通过应用这种技术，发现数值混合与涡旋动能的分布相关。垂直平流引起的数值混合相对较小，并且与浮力通量的分布相关。研究发现，所探讨的高阶方案显示的虚假混合程度可能会局部超过物理混合程度。
{"title":"Discrete variance decay analysis of spurious mixing","authors":"Tridib Banerjee , Sergey Danilov , Knut Klingbeil , Jean-Michel Campin","doi":"10.1016/j.ocemod.2024.102460","DOIUrl":"10.1016/j.ocemod.2024.102460","url":null,"abstract":"<div><div>This work examines the use of discrete variance decay of tracers to estimate locally in space and time the numerical mixing caused by different processes during a tracer transport step. Expressions for local discrete variance decay (DVD) rates are directly derived from discrete tracer equations without any assumptions on discrete fluxes of the second moment. They relate the DVD rates to the fluxes of the first moment through the faces of scalar control cell. Mixing associated with advective and diffusive fluxes is thus estimated. The new framework avoids the need for second-moment flux definition when solved directly on finite-volume cell faces but still invokes certain second-moment fluxes when the face DVD rates are partitioned to cells sharing the face. These implied discrete fluxes depend on the partitioning and are non-unique. For third- or higher-order advection schemes, the DVD rates are contaminated by dispersive errors intrinsic to the approach, introducing uncertainty to the locality of any estimates produced by it. Additional temporal averaging or coarse-graining is thus necessary. Through the application of this technique, numerical mixing is found to be correlated with the distribution of eddy kinetic energy. Numerical mixing induced by vertical advection is found to be relatively small and correlated with the distribution of buoyancy fluxes. The explored high-order schemes are found to demonstrate levels of spurious mixing which may locally exceed physical mixing.</div></div>","PeriodicalId":19457,"journal":{"name":"Ocean Modelling","volume":"192 ","pages":"Article 102460"},"PeriodicalIF":3.1,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-02DOI: 10.1016/j.ocemod.2024.102461
Jian-Guo Li , Peitao Wang
A model of shallow water equations (SWEs) on a spherical multiple-cell (SMC) grid of 4-level (2.5–5–10–20 km) spatial resolutions is used to simulate tsunami propagation on global ocean surfaces. The unstructured SMC grid retains rectangular cells of the longitude-latitude grid so that efficient finite-difference schemes could be used. It also supports multi-resolutions like mesh refinement to resolve small islands and coastline details while keeping models compact enough to fit into available computers. Two earthquake-induced tsunami cases are simulated and compared with available observations. Results indicate that the modelled tsunami arrival times agree well with observations while tsunami wave heights are underestimated, particularly the observed runups on remote coastal lands. Possible reasons for this underestimation include the smoothing scheme used to suppress numerical oscillations and the missing of initial kinetic energy input from the earthquakes. Another reason is the limitation of the SWEs to describe coastal bores and breaking waves in coastal waters. A possible tsunami scenario induced by a landslide in the Canary Islands is also simulated to assess its potential impact on Atlantic coastal regions. Model results indicate that this kind of tsunami may cause severe damage to local areas but its effects on far fields, like the UK and American coastal regions are small. As the initial landslide disturbance is overly simplified, this study does not give a true representation of a real landslide tsunami but rather a qualitative assessment of its impact on the Atlantic Ocean. More realistic initial condition and improved model representation of coastal processes are needed for further studies of this possible landslide hazard.
{"title":"Global tsunami modelling on a spherical multiple-cell grid","authors":"Jian-Guo Li , Peitao Wang","doi":"10.1016/j.ocemod.2024.102461","DOIUrl":"10.1016/j.ocemod.2024.102461","url":null,"abstract":"<div><div>A model of shallow water equations (SWEs) on a spherical multiple-cell (SMC) grid of 4-level (2.5–5–10–20 km) spatial resolutions is used to simulate tsunami propagation on global ocean surfaces. The unstructured SMC grid retains rectangular cells of the longitude-latitude grid so that efficient finite-difference schemes could be used. It also supports multi-resolutions like mesh refinement to resolve small islands and coastline details while keeping models compact enough to fit into available computers. Two earthquake-induced tsunami cases are simulated and compared with available observations. Results indicate that the modelled tsunami arrival times agree well with observations while tsunami wave heights are underestimated, particularly the observed runups on remote coastal lands. Possible reasons for this underestimation include the smoothing scheme used to suppress numerical oscillations and the missing of initial kinetic energy input from the earthquakes. Another reason is the limitation of the SWEs to describe coastal bores and breaking waves in coastal waters. A possible tsunami scenario induced by a landslide in the Canary Islands is also simulated to assess its potential impact on Atlantic coastal regions. Model results indicate that this kind of tsunami may cause severe damage to local areas but its effects on far fields, like the UK and American coastal regions are small. As the initial landslide disturbance is overly simplified, this study does not give a true representation of a real landslide tsunami but rather a qualitative assessment of its impact on the Atlantic Ocean. More realistic initial condition and improved model representation of coastal processes are needed for further studies of this possible landslide hazard.</div></div>","PeriodicalId":19457,"journal":{"name":"Ocean Modelling","volume":"192 ","pages":"Article 102461"},"PeriodicalIF":3.1,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-17DOI: 10.1016/j.ocemod.2024.102448
David E. Gregg , Nigel T. Penna , Christopher Jones , Miguel A. Morales Maqueda
The accuracy of global ocean tide models is assessed in coastal waters of the European North West Shelf to ascertain where higher resolution local (forecast) models are most needed for geophysical and navigational applications, and which global models are most suitable for providing boundary conditions for regional and local tide models. Five recent global ocean tide models (FES2014b, EOT20, TPXO9-atlas-v5, GOT4.10c, and DTU16) are considered, with the models first compared by interpolating them onto common grids and computing the mean absolute deviation at each grid point. Coastline tide gauge and offshore bottom pressure sensor data were collated from several sources to give a total of 279 observation sites for evaluating model accuracy, including observational values from 137 locations that have not previously been released and have therefore not been assimilated into any of the global models tested. The residual errors between each model’s predicted phasor and the corresponding observed phasor were calculated at each observation location, and quantified using the root mean square (RMS) and median absolute residual (MAR) for the eight tidal constituents M2, S2, N2, O1, K1, K2, P1, and Q1. To avoid RMS values being biased by observation point density, a Voronoi-weighted RMS based on the water area of the Voronoi polygon about each observation location was also developed and used. Four zones were defined based on ocean depth to gauge model performance, and model inaccuracy is again demonstrated in near-shore regions. Seven further zones were defined based on geographical areas, which reveals inhomogeneity among the global models. The smallest overall root sum square (RSS) RMS error across all eight constituents arises with FES2014b, although TPXO9-atlas-v5 has the best performance when using the MAR and Voronoi-weighted RMS metrics. Using only the 137 observation sites that have not been assimilated by any model and therefore provide an independent accuracy assessment, FES2014b exhibits the smallest errors at the coastline, with an RSS RMS of 24.46 cm. All models exhibit larger errors with the 137 independent observation sites than with all 279 observation sites, with an average overall increase in RSS RMS error of 12%, and an increase of 30% for coastline tide gauges, highlighting the need for local model development in these areas.
{"title":"Accuracy assessment of recent global ocean tide models in coastal waters of the European North West Shelf","authors":"David E. Gregg , Nigel T. Penna , Christopher Jones , Miguel A. Morales Maqueda","doi":"10.1016/j.ocemod.2024.102448","DOIUrl":"10.1016/j.ocemod.2024.102448","url":null,"abstract":"<div><div>The accuracy of global ocean tide models is assessed in coastal waters of the European North West Shelf to ascertain where higher resolution local (forecast) models are most needed for geophysical and navigational applications, and which global models are most suitable for providing boundary conditions for regional and local tide models. Five recent global ocean tide models (FES2014b, EOT20, TPXO9-atlas-v5, GOT4.10c, and DTU16) are considered, with the models first compared by interpolating them onto common grids and computing the mean absolute deviation at each grid point. Coastline tide gauge and offshore bottom pressure sensor data were collated from several sources to give a total of 279 observation sites for evaluating model accuracy, including observational values from 137 locations that have not previously been released and have therefore not been assimilated into any of the global models tested. The residual errors between each model’s predicted phasor and the corresponding observed phasor were calculated at each observation location, and quantified using the root mean square (RMS) and median absolute residual (MAR) for the eight tidal constituents M2, S2, N2, O1, K1, K2, P1, and Q1. To avoid RMS values being biased by observation point density, a Voronoi-weighted RMS based on the water area of the Voronoi polygon about each observation location was also developed and used. Four zones were defined based on ocean depth to gauge model performance, and model inaccuracy is again demonstrated in near-shore regions. Seven further zones were defined based on geographical areas, which reveals inhomogeneity among the global models. The smallest overall root sum square (RSS) RMS error across all eight constituents arises with FES2014b, although TPXO9-atlas-v5 has the best performance when using the MAR and Voronoi-weighted RMS metrics. Using only the 137 observation sites that have not been assimilated by any model and therefore provide an independent accuracy assessment, FES2014b exhibits the smallest errors at the coastline, with an RSS RMS of 24.46 cm. All models exhibit larger errors with the 137 independent observation sites than with all 279 observation sites, with an average overall increase in RSS RMS error of 12%, and an increase of 30% for coastline tide gauges, highlighting the need for local model development in these areas.</div></div>","PeriodicalId":19457,"journal":{"name":"Ocean Modelling","volume":"192 ","pages":"Article 102448"},"PeriodicalIF":3.1,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527781","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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