Application of the Spectral Nudging on Global Tides Towards a Global Total Water Level Prediction System

2019 ◽  
Author(s):  
Tsubasa Kodaira ◽  
Natacha Bernier ◽  
Keith R. Thompson
Keyword(s):  
Water Level ◽  
Coastal Flooding ◽  
Ocean Model ◽  
Global Ocean ◽  
Total Water ◽  
Spectral Leakage ◽  
Spectral Nudging ◽  
Vector Difference ◽  
Tidal Constituents ◽  
Total Water Level

Abstract With the long-term goal of developing an ensemble forecast system for coastal flooding, we are developing a dynamically-based, numerical model of the global ocean. The model is based on the NEMO framework and has been used to predict global tides and surges in previous studies. This study focuses on the optimization of the joint prediction of both tides and surges, the two main components of total water level that cause coastal flooding. To improve the predictions of the tide we use a modified form of “spectral nudging”. We show this leads to significant improvements in the prediction of the M2 tide in the open ocean, and also in the shallow regions closer to shore where the model is not nudged. The median value of the vector difference of the tidal amplitude based on sea level observations and a data-assimilative model, and the predictions of our ocean model, is reduced from 11.2 cm to 2.66 cm by the nudging. The improvement deteriorates significantly however if additional tidal constituents are included in the model (most notably S2). This is explained in terms of spectral leakage between tidal bands associated with the nudging methodology and a straightforward solution is proposed.

Ensemble Water Level Prediction System: Improving the Representation of Model Uncertainty

2020 ◽  
Author(s):  
Natacha Bernier ◽  
Oleksandr Huziy ◽  
Keith Thompson ◽  
Pengcheng Wang ◽  
Benoit Pouliot ◽  
...  
Keyword(s):  
Water Level ◽  
Gulf Of Maine ◽  
Ocean Model ◽  
Total Water ◽  
Atmospheric Forcing ◽  
Operational Forecasts ◽  
Recent Case Study ◽  
Coastal Water Level ◽  
Total Water Level

<p>Concern over increased flooding and the need for earlier and more reliable risk forecasts motivate the continued development of operational forecasts of coastal water level. We report here on results from a year long ensemble of total water level forecasts calculated using a dynamical ocean model forced with ensemble atmospheric forcing and tidal boundary conditions. We focus on the east coast of Canada. The domain includes the Gulf of St. Lawrence, the Labrador Shelf, the Scotian Shelf, and the Gulf of Maine. The water level ensemble is made of a control and 20 perturbed members. Individual forecasts are produced twice daily for 16 days.</p><p> </p><p>The novelty of the present study is in the exploration of perturbations of the ocean contributions. In addition to examining how uncertainty in atmospheric forcing maps into flood risk, we also explore the feasibility, and impact, of perturbing the ocean tides. We use a recent case study to demonstrate our findings.</p><p> </p>

scholarly journals Developments in large-scale coastal flood hazard mapping

2016 ◽  
Vol 16 (8) ◽  
pp. 1841-1853 ◽  
Author(s):  
Michalis I. Vousdoukas ◽  
Evangelos Voukouvalas ◽  
Lorenzo Mentaschi ◽  
Francesco Dottori ◽  
Alessio Giardino ◽  
...  
Keyword(s):  
Water Level ◽  
Large Scale ◽  
Flood Hazard ◽  
Coastal Flooding ◽  
Hazard Mapping ◽  
Volume Discharge ◽  
Total Water ◽  
Computational Costs ◽  
Coastal Flood ◽  
Total Water Level

Abstract. Coastal flooding related to marine extreme events has severe socioeconomic impacts, and even though the latter are projected to increase under the changing climate, there is a clear deficit of information and predictive capacity related to coastal flood mapping. The present contribution reports on efforts towards a new methodology for mapping coastal flood hazard at European scale, combining (i) the contribution of waves to the total water level; (ii) improved inundation modeling; and (iii) an open, physics-based framework which can be constantly upgraded, whenever new and more accurate data become available. Four inundation approaches of gradually increasing complexity and computational costs were evaluated in terms of their applicability to large-scale coastal flooding mapping: static inundation (SM); a semi-dynamic method, considering the water volume discharge over the dykes (VD); the flood intensity index approach (Iw); and the model LISFLOOD-FP (LFP). A validation test performed against observed flood extents during the Xynthia storm event showed that SM and VD can lead to an overestimation of flood extents by 232 and 209 %, while Iw and LFP showed satisfactory predictive skill. Application at pan-European scale for the present-day 100-year event confirmed that static approaches can overestimate flood extents by 56 % compared to LFP; however, Iw can deliver results of reasonable accuracy in cases when reduced computational costs are a priority. Moreover, omitting the wave contribution in the extreme total water level (TWL) can result in a  ∼  60 % underestimation of the flooded area. The present findings have implications for impact assessment studies, since combination of the estimated inundation maps with population exposure maps revealed differences in the estimated number of people affected within the 20–70 % range.

scholarly journals Deriving the 100-Year Total Water Level around the Coast of Corsica by Combining Trivariate Extreme Value Analysis and Coastal Hydrodynamic Models

2021 ◽  
Vol 9 (12) ◽  
pp. 1347
Author(s):  
Jessie Louisor ◽  
Jérémy Rohmer ◽  
Thomas Bulteau ◽  
Faïza Boulahya ◽  
Rodrigo Pedreros ◽  
...  
Keyword(s):  
Water Level ◽  
Return Period ◽  
Extreme Value ◽  
Coastal Areas ◽  
Extreme Value Analysis ◽  
Total Water ◽  
Hydrodynamic Models ◽  
Value Analysis ◽  
Multivariate Extreme Value ◽  
Total Water Level

As low-lying coastal areas can be impacted by flooding caused by dynamic components that are dependent on each other (wind, waves, water levels—tide, atmospheric surge, currents), the analysis of the return period of a single component is not representative of the return period of the total water level at the coast. It is important to assess a joint return period of all the components. Based on a semiparametric multivariate extreme value analysis, we determined the joint probabilities that significant wave heights (Hs), wind intensity at 10 m above the ground (U), and still water level (SWL) exceeded jointly imposed thresholds all along the Corsica Island coasts (Mediterranean Sea). We also considered the covariate peak direction (Dp), the peak period (Tp), and the wind direction (Du). Here, we focus on providing extreme scenarios to populate coastal hydrodynamic models, SWAN and SWASH-2DH, in order to compute the 100-year total water level (100y-TWL) all along the coasts. We show how the proposed multivariate extreme value analysis can help to more accurately define low-lying zones potentially exposed to coastal flooding, especially in Corsica where a unique value of 2 m was taken into account in previous studies. The computed 100y-TWL values are between 1 m along the eastern coasts and a maximum of 1.8 m on the western coast. The calculated values are also below the 2.4 m threshold recommended when considering the sea level rise (SLR). This highlights the added value of performing a full integration of extreme offshore conditions, together with their dependence on hydrodynamic simulations for screening out the coastal areas potentially exposed to flooding.

scholarly journals The Role of Mean Sea Level Annual Cycle on Extreme Water Levels Along European Coastline

2020 ◽  
Vol 12 (20) ◽  
pp. 3419
Author(s):  
Tomás Fernández-Montblanc ◽  
Jesús Gómez-Enri ◽  
Paolo Ciavola
Keyword(s):  
Water Level ◽  
Sea Level ◽  
North Sea ◽  
Extreme Events ◽  
Annual Cycle ◽  
Coastal Flooding ◽  
Water Levels ◽  
Total Water ◽  
Mean Sea Level ◽  
The Impact

The knowledge of extreme total water levels (ETWLs) and the derived impact, coastal flooding and erosion, is crucial to face the present and future challenges exacerbated in European densely populated coastal areas. Based on 24 years (1993–2016) of multimission radar altimetry, this paper investigates the contribution of each water level component: tide, surge and annual cycle of monthly mean sea level (MMSL) to the ETWLs. It focuses on the contribution of the annual variation of MMSL in the coastal flooding extreme events registered in a European database. In microtidal areas (Black, Baltic and Mediterranean Sea), the MMSL contribution is mostly larger than tide, and it can be at the same order of magnitude of the surge. In meso and macrotidal areas, the MMSL contribution is <20% of the total water level, but larger (>30%) in the North Sea. No correlation was observed between the average annual cycle of monthly mean sea level (AMMSL) and coastal flooding extreme events (CFEEs) along the European coastal line. Positive correlations of the component variance of MMSL with the relative frequency of CFEEs extend to the Central Mediterranean (r = 0.59), North Sea (r = 0.60) and Baltic Sea (r = 0.75). In the case of positive MMSL anomalies, the correlation expands to the Bay of Biscay and northern North Atlantic (at >90% of statistical significance). The understanding of the spatial and temporal patterns of a combination of all the components of the ETWLs shall improve the preparedness and coastal adaptation measures to reduce the impact of coastal flooding.

A Meta-Modelling Approach for Estimating Long-Term Wave Run-Up and Total Water Level on Beaches

2018 ◽  
Vol 342 ◽  
pp. 475-489 ◽  
Author(s):  
June Gainza ◽  
Ana Rueda ◽  
Paula Camus ◽  
Antonio Tomás ◽  
Fernando J. Méndez ◽  
...  
Keyword(s):  
Water Level ◽  
Total Water ◽  
Run Up ◽  
Total Water Level ◽  
Modelling Approach

scholarly journals SYNTHESIS OP HURRICANE RESPONSE HYDROGRAPHS

1982 ◽  
Vol 1 (18) ◽  
pp. 7
Author(s):  
Rodney J. Sobey
Keyword(s):  
Water Level ◽  
Historical Data ◽  
Breaking Wave ◽  
Total Water ◽  
Coastal Site ◽  
Data Set ◽  
Storm Tide ◽  
Synthesis Technique ◽  
Astronomical Tide ◽  
Total Water Level

A hindcasting methodology is described for the total water level and wave hydrographs at a coastal site during a hurricane. It accommodates phasing of the separate components of the sustained water level (astronomical tide, storm tide, breaking wave setup) , as well as storm variability and coastal bathymetry. Complete hindcast models are utilised, but an intermediate cost and precision is achieved by compromising the number of complete hindcast storms, rather than the precision of the hindcast model. A synthesis technique is developed to predict the response hydrographs of the remaining storms in the historical data set.

scholarly journals HURRICANE WATER LEVEL PREDICTION USING SURROGATE MODELING

2018 ◽  
pp. 57
Author(s):  
Jeffrey A. Melby ◽  
Fatima Diop ◽  
Norberto Nadal-Caraballo ◽  
Alex Taflanidis ◽  
Victor Gonzalez
Keyword(s):  
Water Level ◽  
Water Levels ◽  
High Fidelity ◽  
Forward Speed ◽  
Efficient Design ◽  
Total Water ◽  
Training Set ◽  
Kriging Approach ◽  
Total Water Level ◽  
Water Level Prediction

For this study, the surrogate was constructed using kriging (Jia et al. 2015). The high fidelity coupled surge and wave numerical modelling for the Gulf of Mexico was used as the training set. The numerical model was either ADCIRC and STWAVE or ADCIRC and SWAN in the nearshore. The surrogate models were trained using tropical storm parameters (latitude, longitude, central pressure, radius to maximum wind speed, storm heading, and forward speed) at a specific location as inputs and individual responses (e.g. surge) as outputs. Tide was computed separately using ADCIRC and linearly superimposed with surge to get total water level. The regional surrogates accurately reproduced both peaks and time series of water levels for historical storms. An extensive validation was conducted to determine the optimal application of the kriging approach. In this paper we will report the efficient design-of-experiments approach, surrogate training and validation.

Hydrodynamic Study of the Impact of Extreme Flooding Events on Wastewater Treatment Plants Considering Total Water Level

2022 ◽  
Vol 23 (1) ◽  
Author(s):  
Rouzbeh Nazari ◽  
Haralambos Vasiliadis ◽  
Maryam Karimi ◽  
Md Golam Rabbani Fahad ◽  
Stanley Simon ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Water Level ◽  
Wastewater Treatment Plants ◽  
Total Water ◽  
Hydrodynamic Study ◽  
Extreme Flooding ◽  
Flooding Events ◽  
The Impact ◽  
Total Water Level

Extreme Values of Total Water Level and Total Water Velocity in the Arabian Gulf

2008 ◽  
Author(s):  
Richard A. Sproson
Keyword(s):  
Water Level ◽  
Extreme Values ◽  
Water Velocity ◽  
Total Water ◽  
Structure Variable ◽  
Wave Orbital Velocity ◽  
Mean Current ◽  
Total Water Level ◽  
Surge Height ◽  
Crest Height

PERGOS hindcast model data from the north-east coast of Qatar has been analysed in order to estimate extreme values of total water level (crest height + surge height) and total water velocity (wave orbital velocity + in-line current velocity) based on analysis of 103 storms that occurred between 1961 and 2002. The PERGOS hindcast includes significant wave height, peak period, mean wave direction, surge height, depth-mean current speed and depth-mean current direction. Crest height has been derived from the source parameters using Fugro GEOS’ proprietary EXWAN program. Wave orbital velocity has been derived using stream function theory. Extreme values of total water level and total water velocity were estimated by: (i) univariate extremal analysis of the structure variable components, (ii) univariate extremal analysis of the structure variable, and (iii) bivariate extremal analysis of the structure variable components using Fugro GEOS’ proprietary GTMFIT program. The effect of the lag between the peak wave, current and surge events on extreme values of total water level and total water velocity has also been assessed. A reduction in the 10,000-year extreme water velocity of 14–21% and a reduction in the 10,000-year extreme water level of 3–14% have been achieved using the structure variable methods.

scholarly journals Ocean tides under the Filchner-Ronne Ice Shelf, Antarctica

1996 ◽  
Vol 23 ◽  
pp. 217-225 ◽  
Author(s):  
M. J. Smithson ◽  
A. V. Robinson ◽  
R. A. Flather
Keyword(s):  
Friction Coefficient ◽  
Ocean Model ◽  
Global Ocean ◽  
Open Boundary ◽  
Open Boundary Conditions ◽  
Ocean Tides ◽  
Ice Shelf ◽  
Grounding Line ◽  
Preliminary Study ◽  
Tidal Constituents

A depth-averaged finite-difference numerical model has been used to make a preliminary study of the tides under the Filchner–Ronne Ice Shelf. Open boundary conditions were specified using the global ocean model of Schwiderski. Tidal constituents for the two principal semi-diurnal constituents M2 and S2, and the two principal diurnal constituents Ο1 and K1 were extracted from computed sea-surface elevations by harmonic analysis. Measured values near to the grounding line could only be reproduced satisfactorily by increasing the bottom friction coefficient under the ice to 50 times the open-ocean value. This destroys any agreement near the ice front or at pelagic sites. It is thought that a friction coefficient which varies with distance under the ice would be able to reproduce better all the available measurements. More tidal measurements are required to validate any model of the region with model experiments being used to help pinpoint possible sites for instrument deployment.

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