Wind–Wave Modeling: Where We Are, Where to Go

Abstract

We perform a critical analysis of the present approach in wave modeling and of the related results. While acknowledging the good quality of the best present forecasts, we point out the limitations that appear when we focus on the corresponding spectra. Apart from the meteorological input, these are traced back to the spectral approach at the base of the present operational models, and the consequent approximations involved in properly modeling the various physical processes at work. Future alternatives are discussed. We then focus our attention on how, given the situation, to deal today with the estimate of the maximum wave heights, both in the long term and for a specific situation. For this, and within the above limits, a more precise evaluation of the wave spectrum is shown to be a mandatory condition.The contemporary, and complementary, theories by Phillips [3] and Miles [4] on wave generation soon followed. On the basis of the Phillips framing of the problem, Hasselmann [5] quantified the interactions and conservative exchange of energy among the spectral components. White-capping, the energy loss by wave crests breaking in deep water, had to wait 17 years after the formulation of the input function before Hasselmann [6], in connection with the JONSWAP (JOint North Sea WAve Project) experiments and report [7], proposed an empirical, but at least quantified and spectrum-dependent, usable expression suitable for practical applications. The adult age of wave modeling was finally reached in 1988 [8] with the reduced Discrete Interaction Approximation (DIA) parameterization [9] of the non-linear interactions, and the consequent formulation of the first third-generation model WAM. The overall situation was well pictured in the so-called WAM book by Komen et al. [10]. Other models followed on the same route: WAVEWATCH [11], SWAN [12], and the one by the Danish Hydraulic Institute.Today we live in a slow evolution of the 1994 situation. Improvements have been made on some aspects of the source functions, computers are faster, and we have gone to progressively higher resolutions. However, although with a rather crude statement, we can say that most of our improvements in the last three decades have been associated with the parallel improvements in the definition and accuracy of the driving wind fields. Indeed, during the last 30 years the only basic conceptual improvement has been the acknowledgement by Janssen [13] of the two-way interaction with the atmosphere, and the consequent need to use a coupled model. Including the interaction with ocean currents, the process is still on its way.

Correlation of Concurrent Extreme Metocean Hazards Considering Seasonality

“…For the proposal briefly outlined in the four steps of the previous section, it is noted that for step (1) the T -yr values of Hs are related to the GEV model, but any projected return level of the significant wave height available to the designer could be useful, at least as an approximation. Also, since for any given month selected, two options are available in step (2), namely, Equation (8) or Equation (10), the decision for the more suitable option can be based on the ε V reported in Table 1, as well as on Figures 7, 10 and 11 and Figures A1-A9. Justification for considering Hs and V w for T -yr in step (3) as simultaneously occurring metocean variables is based not only on the correlation of recorded (observed) data, but also in checking that the correlation of projected Hs and V w for T -yr , obtained from the time-dependent GEV models, are consistent with the trend of the observed data.…”

“…Recent studies on extreme waves and winds include the assessment of significant wave heights in the South China Sea using hindcast data [4], wind models to simulate waves in the South China Sea and the East China Sea [5], the use of radar images to estimate significant wave height [6], wave height forecasting during extreme events [7], assessment of wave heights by using generalized Pareto and Gumbel distributions [8], uncertainty assessment in extreme significant wave height by using different techniques [9] and a review on available wind-wave models and their limitations [10]. Additionally, hindcast for wind-wave for several decades was calculated and compared with observed data for estimating wave climate change and…”

Selected Papers from the Future Paths and Needs in Wave Modelling Workshop

“…Cavaleri et al [1] present a critical analysis of the state-of-the-art approach within 3D ocean wave spectrum modelling, which forms the input to all ocean engineering and naval architecture applications in the local modelling relevant to structures. It is argued that many major developments were made 25 years ago and earlier, and there is now a need to step forward.…”

“…A better representation of the dynamic two-way interaction between the wind and propagating wave fields is needed according to [1]; the two fields should preferably be considered as one integrated domain. This also includes the wave breaking phenomenon.…”

“…As an outcome of the International Workshop "Future needs and challenges in wave modelling", held by SINTEF in Trondheim, Norway, 21-22 October 2019, this Special Issue includes 10 full Journal scientific papers [1][2][3][4][5][6][7][8][9][10] and two Technical notes [11,12], which have been prepared based on a selection of the Workshop presentations. All publications were peer-reviewed according to Journal standards by international experts.…”