ØS

Øyvind Sætra

Norwegian Meteorological Institute

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ØB

Øyvind Breivik

Norwegian Meteorological Institute

Ana Carrasco

Norwegian Meteorological Institute

ÁS

Álvaro Semedo

IHE Delft Institute for Water Education

Ole Christian Lind

Norwegian University of Life Sciences

Magne Simonsen

Norwegian Meteorological Institute

Nils Melsom Kristensen

Norwegian Meteorological Institute

Ole Johan Aarnes

Equinor (Norway)

Jon Albretsen

Norwegian Institute of Marine Research

Torsten Linders

University of Gothenburg

Jean‐Raymond Bidlot

European Centre for Medium-Range Weather Forecasts

Cooperative Institutions

Norwegian Meteorological Institute

University of Oslo

University of Bergen

Bjerknes Centre for Climate Research

Norwegian University of Life Sciences

University of Sheffield

MSD (Spain)

Universität Hamburg

Centre National de la Recherche Scientifique

European Centre for Medium-Range Weather Forecasts

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Coastal transport of river-discharged radionuclides: Impact of speciation and transformation processes in numerical model simulations

The Science of The Total Environment (2019)

Magne Simonsen Ole Christian Lind Øyvind Sætra Pål Erik Isachsen Hans‐Christian Teien

Settling

Genetic algorithm

Particle (ecology)

10.1016/j.scitotenv.2019.01.434

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Citations (24)

Effect of film elasticity on the drift velocity of capillary–gravity waves

Physics of Fluids (1995)

Jan Erik H. Weber Øyvind Sætra

The effect of an insoluble, elastic surface film on the drift velocity of capillary–gravity waves is studied theoretically on the basis of a Lagrangian description of motion. There is no forcing from the atmosphere, and the wave amplitude is taken to attenuate in time. Defining a nondimensional parameter α, which combines film elasticity, fluid viscosity, and wave frequency, maximum damping of the linear waves occurs when α=1 (the Marangoni effect). In this case the frequency of capillary–gravity waves nearly coincides with that of elastic film waves. The nonlinear drift velocity is obtained for general values of α. In particular, it is found that the absolute maximum of the transient drift current is located below the surface when α≳2/3. At the surface, maximum drift velocity (in time domain) occurs for values of α that are somewhat less than one.

Capillary wave

Stokes drift

10.1063/1.868629

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Citations (18)

Effect of Film Elasticity on Drift Currents Induced by Growing Waves

Fluid mechanics and its applications (1996)

Øyvind Sætra Jan Erik H. Weber

Elasticity

10.1007/978-94-009-0253-4_13

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Citations (0)

High Resolution Modeling of Aluminium Transport in a Fjord Estuary with Focus on Mean Circulation and Irregular Flow Events

SSRN Electronic Journal (2022)

Magne Simonsen Jon Albretsen Øyvind Sætra Lars Asplin Ole Christian Lind

Assessment of environmental impacts of trace metals and radionuclides in estuarine waters will benefit from numerical transport models that can provide detailed and accurate predictions of concentrations of harmful physico-chemical forms (species) of the contaminants at adequate spatial and temporal resolution. In the present work, a transport model (OpenDrift) including dynamic speciation and transformation processes was improved and applied, using three-dimensional hydrodynamic flow fields from a numerical ocean model (ROMS) at high horizontal resolution (32m). Using numerical trajectories, the transport and concentration of aluminium (Al) was computed along the estuary and fjord of Sandnesfjorden in south-eastern Norwayfrom the river outlet to the open coastal waters.Validation of the model system with hydrographic profiles and Al concentration in surface samples from 12 locations showed improvements compared to previous studies due to optimization of model configuration. Model results showed good agreement with observed surface values. The along-fjord decreasing trend and the increased concentration in the estuary was well reproduced. However, the transport modeling gave a more detailed site-specific picture of the Al concentration and suggested more scattered and variable fields than what was indicated by the observational data. Our results demonstrate a considerable mixing and redistribution of the water masses during reversed flow events (surface flow into the fjord). This affected both the horizontal mixing of river discharges with coastal water as well as vertically when surface water was mixed with deeper water masses. Such blocking events were shown to have significant impact on the properties and distribution of the water masses causing increased concentrations of Al in the fjord and may potentially have severe impact on biota. This should therefore be considered in cases involving interpretation of transport estimates of contaminants in fjords and coastal regions, where high exposure locations can be significantly higher than average values.

Fjord

Estuarine water circulation

Circulation (fluid dynamics)

10.2139/ssrn.4249976

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Citations (0)

Mesoscale Numerical Modelling of Met-ocean Interactions

Energy Procedia (2015)

Jakob Kristoffer Süld Adil Rasheed Jørn Kristiansen Øyvind Sætra Ana Carrasco

Abstract Offshore wind energy compared to its onshore counterpart appears more attractive due to its lesser visual impact and lesser issues related to land acquisition. Relatively more convenient accessibility to open sea allows for the installation of larger and larger turbines capable of producing much more power resulting in far lesser number of turbines per wind farm to produce the same amount of power. However, the large size of the turbines (≈ 200 m ) implies that they have to operate in conditions affected by phenomena characteristic of marine boundary layer. Complete inversion of wind profiles close to coasts, strong high waves and their interaction with the structures supporting the turbines can have a profound influence on the performance of wind turbines and their life time. A lot of development is taking place in the area of numerical and experimental modeling of wind turbines and its support structures but those studies are generally conducted for idealized cases. In reality the conditions can be markedly different. In order to understanding the behavior of turbines in operational condition, a good understanding of the marine boundary layer and ocean waves is an obvious prerequisite. In the current paper we explain the coupling of an atmospheric code HARMONIE using AROME physics with the ocean wave model WAM. Some preliminary results related to the effects of coupling on wind speed and significant wave height are presented for a few sites close to the Norwegian coast.

10.1016/j.egypro.2015.11.447

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Citations (3)

Wave‐induced transport and vertical mixing of pelagic eggs and larvae

Limnology and Oceanography (2014)

Johannes Röhrs Kai H. Christensen Frode B. Vikebø Svein Sundby Øyvind Sætra

The transport of pelagic plankton by wind‐driven ocean currents and surface gravity waves is investigated for the example of Northeast Arctic cod eggs and larvae on the coast of northern Norway. Previous studies indicate that the wave‐induced drift (i.e., Stokes drift) is relevant for the transport of particles in the upper ocean. We use an ocean general circulation model together with a numerical wave prediction model and a Lagrangian particle tracking model to calculate trajectories of fish eggs and larvae. Waves are considered not only for particle drift but also for the air—sea momentum flux, its contribution to the Coriolis force, and vertical mixing. The sample species provides the advantage that many of its physical and behavioral properties are well known (e.g., egg buoyancy), allowing investigation of vertical particle displacement by turbulent mixing in response to wind forcing and wave breaking. The approach accounting for particle mixing by breaking waves enhances agreement between observed and modeled egg profiles. Results also show a general shoreward transport of particles by the Stokes drift. This wave drift exhibits a more constant direction than the Eulerian current and hence stabilizes particle diffusion to favor a dominant direction. For the case of Northeast Arctic cod, waves concentrated model eggs and larvae on average 1.5 km closer to shore, which is 20% of their total distance to the coast. This increases the residence time of first‐feeding larvae close to the spawning areas compared to earlier models.

Stokes drift

Lagrangian particle tracking

10.4319/lo.2014.59.4.1213

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Citations (78)

Future wind, wave and storm surge climate in the northern North Atlantic

Climate Research (2002)

Jens Boldingh Debernard Øyvind Sætra LP Røed

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 23:39-49 (2002) - doi:10.3354/cr023039 Future wind, wave and storm surge climate in the northern North Atlantic Jens Debernard*, Øyvind Sætra, Lars Petter Røed Research and Development Division, Norwegian Meteorological Institute, PO Box 43, Blindern, 0313 Oslo, Norway *Email: jens.debernard@met.no ABSTRACT: In this paper we consider a possible change in future wind, wave, and storm surge climate for the regional seas northeast of the Atlantic: the northern North Atlantic. Conclusions are based on a statistical analysis of the results derived with state-of-the-art wave and storm surge models run for two 20 yr time-slice periods, one for the period 1980 to 2000 (control climate) and one for the period 2030 to 2050 (future climate). Forcing was derived by extracting atmospheric wind and sea level pressure from a state-of-the-art regional atmospheric climate model for the same two 20 yr periods. These regional atmospheric simulations constitute dynamical downscales of the Max Planck Institute¹s global scenario which includes greenhouse gases, sulphate aerosols (direct and indirect effects) and tropospheric ozone. Generally the changes we found are small. However, there are some important exceptions, such as a significant increase in all variables in the Barents Sea and a significant reduction in wind and waves north and west of Iceland. Also, there is a significant increase in wind speed in the northern North Sea and westwards in the Atlantic Ocean, and a comparable reduction southwest of the British Isles in the autumn. The same change is suggested for wave height, but this is not statistically significant. There is a significant increase in the seasonal 99 percentile of the sea level in autumn in the southwest part of the North Sea. These results are consistent with earlier studies predicting a rougher maritime climate in the northern North Sea in autumn. KEY WORDS: Dynamical downscaling · Sea state · Climate change · Wave climate · Surge climate Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 23, No. 1. Online publication date: December 20, 2002 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2002 Inter-Research.

Storm Surge

10.3354/cr023039

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Citations (82)

Bias Correction of Operational Storm Surge Forecasts Using Neural Networks

arXiv (Cornell University) (2023)

Paulina Tedesco Jean Rabault Martin Lilleeng Sætra Nils Melsom Kristensen Ole Johan Aarnes

Storm surges can give rise to extreme floods in coastal areas. The Norwegian Meteorological Institute produces 120-hour regional operational storm surge forecasts along the coast of Norway based on the Regional Ocean Modeling System (ROMS), using a model setup called Nordic4-SS. Despite advances in the development of models and computational capabilities, forecast errors remain large enough to impact response measures and issued alerts, in particular, during the strongest events. Reducing these errors will positively impact the efficiency of the warning systems while minimizing efforts and resources spent on mitigation. Here, we investigate how forecasts can be improved with residual learning, i.e., training data-driven models to predict the residuals in forecasts from Nordic4-SS. A simple error mapping technique and a more sophisticated Neural Network (NN) method are tested. Using the NN residual correction method, the Root Mean Square Error in the Oslo Fjord is reduced by 36% for lead times of one hour and 9% for 24 hours. Therefore, the residual NN method is a promising direction for correcting storm surge forecasts, especially on short timescales. Moreover, it is well adapted to being deployed operationally, as i) the correction is applied on top of the existing model and requires no changes to it, ii) all predictors used for NN inference are already available operationally, iii) prediction by the NNs is very fast, typically a few seconds per station, and iv) the NN correction can be provided to a human expert who may inspect it, compare it with the model output, and see how much correction is brought by the NN, allowing to capitalize on human expertise as a quality validation of the NN output. While no changes to the hydrodynamic model are necessary to calibrate the neural networks, they are specific to a given model and must be recalibrated when the numerical models are updated.

Storm Surge

10.48550/arxiv.2301.00892

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Citations (0)

NORA-Surge: A storm surge hindcast for the Norwegian Sea, the North Sea and the Barents Sea

Ocean Modelling (2024)

Nils Melsom Kristensen Paulina Tedesco Jean Rabault Ole Johan Aarnes Øyvind Sætra

Knowledge about statistics for water level variations along the coast due to storm surge is important for the utilization of the coastal zone. An open and freely available storm surge hindcast archive covering the coast of Norway and adjacent sea areas spanning the time period 1979–2022 is presented. The storm surge model is forced by wind stress and mean sea level pressure taken from the non-hydrostatic NORA3 atmospheric hindcast. A dataset consisting of observations of water level from more than 90 water level gauges along the coasts of the North Sea and the Norwegian Sea is compiled and quality controlled, and used to assess the performance of the hindcast. The observational dataset is distributed in both time and space, and when considering all the available quality controlled data, the comparison with modeled water levels yield a mean absolute error (MAE) of 9.7 cm and a root mean square error (RMSE) of 12.4 cm. Values for MAE and RMSE scaled by the standard deviation of the observed storm surge for each station are 0.42 and 0.54 standard deviations, respectively. When considering the geographical differences in characteristics of storm surge for different countries/regions, the values of MAE and RMSE are in the range 5.7–13.9 cm and 7.6–17.8 cm respectively, and 0.33–0.46 and 0.42–0.59 standard deviations for the scaled values. The minimum and maximum values for water level in the hindcast are −2.60 m and 3.92 m. In addition, 100-year return level estimates are calculated from the hindcast, with minimum and maximum values of, respectively, −2.75 m and 3.98 m. All minimum and maximum values are found in the southern North Sea area.

Hindcast

Storm Surge

Tide gauge

Wind Stress

10.1016/j.ocemod.2024.102406

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Citations (0)

Potential Benefits of Using Probabilistic Forecasts for Waves and Marine Winds Based on the ECMWF Ensemble Prediction System

Weather and Forecasting (2004)

Øyvind Sætra Jean‐Raymond Bidlot

The potential benefits of using the ECMWF Ensemble Prediction System (EPS) for waves and marine surface winds are demonstrated using buoy and platform data as well as altimeter data. For forecasting purposes, the spread of the different forecasts in the ensemble may indeed be regarded as a measure of the uncertainties in the deterministic predictions. In order to demonstrate this point, a new method is presented in which the ensemble spread is divided into different classes. An upper bound for the model errors is established by calculating the corresponding percentiles of the errors for each separate class. Using this upper bound for the model errors, a strong correlation between the ensemble spread and the deterministic forecast skill is shown. The reliability of the probability forecasts as derived from the EPS for wind and waves is found to be good. However, the reliability diagrams indicate a small tendency for overconfidence in the wave probability forecasts for waves above 6 and 8 m. This is most pronounced in the Southern Hemisphere, whereas the reliability for the Northern Hemisphere is relatively good. The impact of using of the wave EPS in decision making is studied by a cost–loss model for the relative economic value. For comparison, poor-man's ensembles (PMEs) are also created by adding normally distributed noise to the control forecasts. This study reveals that the real EPS performs better than both the PME and the control forecasts in terms of relative economic value. When more complex forecasting parameters are considered, such as the joint probability of wave height and period, benefits of using the EPS become even more pronounced.

Consensus forecast

Probabilistic Forecasting

Buoy

Significant wave height

10.1175/1520-0434(2004)019<0673:pboupf>2.0.co;2

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Citations (57)