Wave height

About: Wave height is a research topic. Over the lifetime, 5920 publications have been published within this topic receiving 100257 citations.

Marine Wind and Wave Height Trends at Different ERA-Interim Forecast Ranges

Abstract: Trends in marine wind speed and significant wave height are investigated using the global reanalysis ERA-Interim over the period 1979–2012, based on monthly-mean and monthly-maximum data. Besides the traditional reanalysis, the authors include trends obtained at different forecast range, available up to 10 days ahead. Any model biases that are corrected differently over time are likely to introduce spurious trends of variable magnitude. However, at increased forecast range the model tends to relax, being less affected by assimilation. Still, there is a trade-off between removing the impact of data assimilation at longer forecast range and getting a lower level of uncertainty in the predictions at shorter forecast range. Because of the sheer amount of assimilations made in ERA-Interim, directly and indirectly affecting the data, it is difficult, if not impossible, to distinguish effects imposed by all updates. Here, special emphasis is put on the introduction of wave altimeter data in August 1991, ...

Tsunamis : forces on a vertical wall caused by long waves, bores, and surges on a dry bed

Abstract: The major objective of this study has been to investigate experimentally the forces and overturning moments produced by tsunamis on vertical walls. The experimental results are compared with several analytical and numerical models. Several types of waves were used in a horizontal tank including solitary waves, undular bores, turbulent bores, and surges on a dry bed. Bores produced from breaking solitary waves in a tilting wave tank were also investigated. Various measurements were made, including the incident wave celerity, the wave profile, the runup, force, overturning moment, and pressure time histories. The impact process of the bores in the tilting wave tank were recorded with high-speed movies. The wave profiles in the horizontal tank were defined using a laser induced-fluorescence system (LIF) which allows the free surface on a two-dimensional plane in the center of the wave tank to be recorded. This method was developed to measure accurately the surface elevation profile of turbulent high-speed flows which is difficult to measure reliably either with conventional flow visualization techniques or intrusive devices such as wave gages. The LIF method was also used to determine the runup on the wall. Strong vertical accelerations were shown to occur during the reflection of bores and steep solitary waves at a vertical wall. These reduced the force on the wall relative to a hydrostatic force computed from the maximum runup height on the wall. The accelerations also cause the maximum force to occur before and after the maximum runup for steep solitary waves and bores, respectively. For these cases, the maximum measured force and overturning moment were always less than computed from the maximum measured runup on the wall using hydrostatic considerations. The maximum force due to surges on a dry bed was also less than the hydrostatic force calculated from the maximum runup height on the wall. For all the dry bed cases studied, the maximum runup height on the wall was between 1.46 and 1.62 times the velocity head computed from the celerity of the incident surge. For the entire range of wave conditions of this study, the maximum relative runup occurred for a bore with a relative wave height of 1.23, and produced a runup equal to 3.8 times the velocity head computed from the wave celerity. The maximum measured water surface slopes along the front of long waves, bores, and dry bed surges were computed from the measured wave profiles. At the transition from undular bores to turbulent bores, there was a discontinuity in the maximum water surface slope where the slope increased by a factor of 2.5 to three for turbulent bores. This discontinuity corresponded with a rapid increase in the measured runup, force, and moment on the wall. The properly normalized force on a vertical wall due to the impingement of a bore on a mildly sloping beach is shown to be equivalent to the force produced by a bore of constant volume on a horizontal bed. This implies the results from the horizontal wave tank experiments can be used to estimate the loads expected from bores propagating on mild beaches with slopes ranging up to 0.02m/m. Two numerical models were compared with the experimental results. A boundary integral element model, which solves the potential flow problem subject to the full nonlinear free surface boundary conditions, predicted the loads imposed on the wall due to steep solitary waves quite well. A finite difference model of the Navier-Stokes equations was also used to simulate the reflection of solitary waves and mild turbulent bores at a vertical wall. This finite difference model predicted the solitary wave loads quite well; however, it over-predicted the steepness of the incident bore profiles and produced a force-time history with a high amplitude and short-duration peak, which was not observed in the measurements. Except for this sharp peak, the agreement of the finite difference model with the experimental results was quite reasonable.

Is the Intensifying Wave Climate of the U.S. Pacific Northwest Increasing Flooding and Erosion Risk Faster Than Sea-Level Rise?

Abstract: The relative contributions of sea-level rise (SLR) and increasing extratropical storminess to the frequency with which waves attack coastal features is assessed with a simple total water level (TWL) model. For the coast of the U.S. Pacific Northwest over the period of wave- buoy observations (approximately 30 years), wave height (and period) increases have had a more significant role in the increased frequency of coastal flooding and erosion than has the rise in sea level. Where tectonic-induced vertical land motions are significant and coastlines are pres- entlyemergent relativetothemeansealevel,increasingwave heightsresultinthesestretchesofcoastbeingpossiblysubmergentrelativetothe TWL. Although it is uncertain whether wave height increases will continue into the future, it is clear that this process could remain more im- portant than, or at least as important as, SLR for the coming decades, and needs to be taken into account in terms of the increasing exposure of coastal communities and ecosystems to flooding and erosion. DOI: 10.1061/(ASCE)WW.1943-5460.0000172. © 2013 American Society of Civil Engineers.