A comparison between measured wave properties and simple wave hindcasting models in shallow water

Significant wave heights and wave periods obtained from field measurements in Lake Balaton, Hungary, were compared with two versions of the shallow water wave hindcasting model published by the U.S. Army Corps of Engineers. The version presented in CERC [3, 4] was found to give very good hindcasts of wave height but fall —20% low on wave period. The model presented in CERC [5] was 15-20% above the earlier version at long fetches and approximately equivalent at shorter fetches

A comparison of the nonlinear frictional characteristics of two-dimensional and three-dimensional models of a shallow tidal embayment

The nonlinear frictional behavior of two-dimensional (2-D) and three-dimensional (3-D) models are compared in this study of tides in the Bight of Abaco. The shallow depths and the existence of an extensive set of tidal elevation data (five astronomical and two overtide constituents at 25 stations) from Filloux and Snyder (1979) offer an excellent opportunity to compare the effects of different frictional formulations. In addition, previous modeling efforts in the bight have consistently overpredicted the M6and generally overdamped the O1, K1, and S2tides. The results indicate that although the 2-D and 3-D models may be calibrated to produce nearly identical responses for the dominant M2tide, there are systematic differences in the responses of the primary overtides. These differences are explained using analytical expansions of the friction terms and are shown to be due to differences in the terms that are nonlinear in velocity and in water level. The investigation concludes that the overgeneration of M6and the overdamping of secondary astronomical tides will occur in 3-D models as well as 2-D models. Although several causes for these problems were considered, improvement in these constituents could be achieved only by modifying the standard quadratic friction or flow-dependent eddy viscosity relations to reduce the nonlinear frictional effect relative to the linear frictional effect. The required modifications suggest the presence of a constant background velocity, residual turbulence field, or possibly the need for a more advanced frictional closure

Forecasting the coastal ocean: Resolution, tide and operational data in the South Atlantic Bight

This paper addresses shelf-scale simulation with dominant open-water boundary conditions obtained by inversion of interior data. Important, established operational data streams are located along the shore of the study area, in areas influenced strongly by the local geometry. Failure to properly resolve the modeled near field surrounding these data results in their incorrect interpretation, causing invalid inversions and erroneous field estimates far across the shelf. Specifically, improving the model fit to the unresolved data leads to skill degeneration farther offshore and generally unacceptable field estimates remarkably far from shore. Proper near-field resolution leads to valid interpretation and inversion of the same data, with high inverse skill apparent across the shelf. The resolution required is within reach of today's technology

Scalability of an Unstructured Grid Continuous Galerkin Based Hurricane Storm Surge Model

This paper evaluates the parallel performance and scalability of an unstructured grid Shallow Water Equation (SWE) hurricane storm surge model. We use the ADCIRC model, which is based on the generalized wave continuity equation continuous Galerkin method, within a parallel computational framework based on domain decomposition and the MPI (Message Passing Interface) library. We measure the performance of the model run implicitly and explicitly on various grids. We analyze the performance as well as accurracy with various spatial and temporal discretizations. We improve the output writing performance by introducing sets of dedicated writer cores. Performance is measured on the Texas Advanced Computing Center Ranger machine. A high resolution 9,314,706 finite element node grid with 1s time steps can complete a day of real time hurricane storm surge simulation in less than 20 min of computer wall clock time, using 16,384 cores with sets of dedicated writer cores

U.S. IOOS coastal and ocean modeling testbed: Evaluation of tide, wave, and hurricane surge response sensitivities to mesh resolution and friction in the Gulf of Mexico: IOOS TESTBED-RESOLUTION AND FRICTION

This paper investigates model response sensitivities to mesh resolution, topographical details, bottom friction formulations, the interaction of wind waves and circulation, and nonlinear advection on tidal and hurricane surge and wave processes at the basin, shelf, wetland, and coastal channel scales within the Gulf of Mexico. Tides in the Gulf of Mexico are modestly energetic processes, whereas hurricane surge and waves are highly energetic. The unstructured-mesh, coupled wind-wave and circulation modeling system, SWAN+ ADCIRC, is implemented to generate modeled tidal harmonic constituents and hurricane waves and surge for a Hurricane Ike (2008) hindcast. In the open ocean, mesh resolution requirements are less stringent in achieving accurate tidal signals or matching hurricane surge and wave responses; however, coarser resolution or the absence of intertidal zones decreases accuracy along protected nearshore and inland coastal areas due to improper conveyance and/or lateral attenuation. Bottom friction formulations are shown to have little impact on tidal signal accuracy, but hurricane surge is much more sensitive, especially in shelf waters, where development of a strong shore-parallel current is essential to the development of Ike's geostrophic setup. The spatial and temporal contributions of wave radiation stress gradients and nonlinear advection were charted for Ike. Nonlinear advection improves model performance by capturing an additional 10―20 cm of geostrophic setup and increasing resonant cross-shelf waves by 30―40 cm. Wave radiation stress gradients improve performance at coastal stations by adding an extra 20―40 cm to water levels

US IOOS coastal and ocean modeling testbed: Inter-model evaluation of tides, waves, and hurricane surge in the Gulf of Mexico

A Gulf of Mexico performance evaluation and comparison of coastal circulation and wave models was executed through harmonic analyses of tidal simulations, hindcasts of Hurricane Ike (2008) and Rita (2005), and a benchmarking study. Three unstructured coastal circulation models (ADCIRC, FVCOM, and SELFE) validated with similar skill on a new common Gulf scale mesh (ULLR) with identical frictional parameterization and forcing for the tidal validation and hurricane hindcasts. Coupled circulation and wave models, SWAN+ADCIRC and WWMII+SELFE, along with FVCOM loosely coupled with SWAN, also validated with similar skill. NOAA\u27s official operational forecast storm surge model (SLOSH) was implemented on local and Gulf scale meshes with the same wind stress and pressure forcing used by the unstructured models for hindcasts of Ike and Rita. SLOSH\u27s local meshes failed to capture regional processes such as Ike\u27s forerunner and the results from the Gulf scale mesh further suggest shortcomings may be due to a combination of poor mesh resolution, missing internal physics such as tides and nonlinear advection, and SLOSH\u27s internal frictional parameterization. In addition, these models were benchmarked to assess and compare execution speed and scalability for a prototypical operational simulation. It was apparent that a higher number of computational cores are needed for the unstructured models to meet similar operational implementation requirements to SLOSH, and that some of them could benefit from improved parallelization and faster execution speed

Once and Future Gulf of Mexico Ecosystem: Restoration Recommendations of an Expert Working Group

The Deepwater Horizon (DWH) well blowout released more petroleum hydrocarbons into the marine environment than any previous U.S. oil spill (4.9 million barrels), fouling marine life, damaging deep sea and shoreline habitats and causing closures of economically valuable fisheries in the Gulf of Mexico. A suite of pollutants—liquid and gaseous petroleum compounds plus chemical dispersants—poured into ecosystems that had already been stressed by overfishing, development and global climate change. Beyond the direct effects that were captured in dramatic photographs of oiled birds in the media, it is likely that there are subtle, delayed, indirect and potentially synergistic impacts of these widely dispersed, highly bioavailable and toxic hydrocarbons and chemical dispersants on marine life from pelicans to salt marsh grasses and to deep-sea animals. As tragic as the DWH blowout was, it has stimulated public interest in protecting this economically, socially and environmentally critical region. The 2010 Mabus Report, commissioned by President Barack Obama and written by the secretary of the Navy, provides a blueprint for restoring the Gulf that is bold, visionary and strategic. It is clear that we need not only to repair the damage left behind by the oil but also to go well beyond that to restore the anthropogenically stressed and declining Gulf ecosystems to prosperity-sustaining levels of historic productivity. For this report, we assembled a team of leading scientists with expertise in coastal and marine ecosystems and with experience in their restoration to identify strategies and specific actions that will revitalize and sustain the Gulf coastal economy. Because the DWH spill intervened in ecosystems that are intimately interconnected and already under stress, and will remain stressed from global climate change, we argue that restoration of the Gulf must go beyond the traditional "in-place, in-kind" restoration approach that targets specific damaged habitats or species. A sustainable restoration of the Gulf of Mexico after DWH must: 1. Recognize that ecosystem resilience has been compromised by multiple human interventions predating the DWH spill; 2. Acknowledge that significant future environmental change is inevitable and must be factored into restoration plans and actions for them to be durable; 3. Treat the Gulf as a complex and interconnected network of ecosystems from shoreline to deep sea; and 4. Recognize that human and ecosystem productivity in the Gulf are interdependent, and that human needs from and effects on the Gulf must be integral to restoration planning. With these principles in mind, the authors provide the scientific basis for a sustainable restoration program along three themes: 1. Assess and repair damage from DWH and other stresses on the Gulf; 2. Protect existing habitats and populations; and 3. Integrate sustainable human use with ecological processes in the Gulf of Mexico. Under these themes, 15 historically informed, adaptive, ecosystem-based restoration actions are presented to recover Gulf resources and rebuild the resilience of its ecosystem. The vision that guides our recommendations fundamentally imbeds the restoration actions within the context of the changing environment so as to achieve resilience of resources, human communities and the economy into the indefinite future

A Once and Future Gulf of Mexico Ecosystem: Restoration Recommendations of an Expert Working Group

The Deepwater Horizon (DWH) well blowout released more petroleum hydrocarbons into the marine environment than any previous U.S. oil spill (4.9 million barrels), fouling marine life, damaging deep sea and shoreline habitats and causing closures of economically valuable fisheries in the Gulf of Mexico. A suite of pollutants — liquid and gaseous petroleum compounds plus chemical dispersants — poured into ecosystems that had already been stressed by overfishing, development and global climate change. Beyond the direct effects that were captured in dramatic photographs of oiled birds in the media, it is likely that there are subtle, delayed, indirect and potentially synergistic impacts of these widely dispersed, highly bioavailable and toxic hydrocarbons and chemical dispersants on marine life from pelicans to salt marsh grasses and to deep-sea animals. As tragic as the DWH blowout was, it has stimulated public interest in protecting this economically, socially and environmentally critical region. The 2010 Mabus Report, commissioned by President Barack Obama and written by the secretary of the Navy, provides a blueprint for restoring the Gulf that is bold, visionary and strategic. It is clear that we need not only to repair the damage left behind by the oil but also to go well beyond that to restore the anthropogenically stressed and declining Gulf ecosystems to prosperity-sustaining levels of historic productivity. For this report, we assembled a team of leading scientists with expertise in coastal and marine ecosystems and with experience in their restoration to identify strategies and specific actions that will revitalize and sustain the Gulf coastal economy. Because the DWH spill intervened in ecosystems that are intimately interconnected and already under stress, and will remain stressed from global climate change, we argue that restoration of the Gulf must go beyond the traditional “in-place, in-kind” restoration approach that targets specific damaged habitats or species. A sustainable restoration of the Gulf of Mexico after DWH must: 1. Recognize that ecosystem resilience has been compromised by multiple human interventions predating the DWH spill; 2. Acknowledge that significant future environmental change is inevitable and must be factored into restoration plans and actions for them to be durable; 3. Treat the Gulf as a complex and interconnected network of ecosystems from shoreline to deep sea; and 4. Recognize that human and ecosystem productivity in the Gulf are interdependent, and that human needs from and effects on the Gulf must be integral to restoration planning. With these principles in mind, we provide the scientific basis for a sustainable restoration program along three themes: 1. Assess and repair damage from DWH and other stresses on the Gulf; 2. Protect existing habitats and populations; and 3. Integrate sustainable human use with ecological processes in the Gulf of Mexico. Under these themes, 15 historically informed, adaptive, ecosystem-based restoration actions are presented to recover Gulf resources and rebuild the resilience of its ecosystem. The vision that guides our recommendations fundamentally imbeds the restoration actions within the context of the changing environment so as to achieve resilience of resources, human communities and the economy into the indefinite future