THE USE OF SPATIAL RADAR OBSERVATIONS IN WAVE HINDCASTS

Caroline Gautier, Jacco Groeneweg

Abstract


Ten years ago, an extensive measurement has been set up in the tidal inlet of Ameland, to obtain validation data in tidal inlets. Then the focus was on buoy measurements. In addition to these scarce point measurements wave radar data became available two years ago. The aim of this paper is to gain insight in the use and reliability of the wave radar data by comparing the radar data with SWAN model results in a storm hindcast in the Wadden Sea. In order to use the SWAN results as a benchmark the SWAN model performance was assessed first by comparing the model results with buoy measurements. In the comparison between radar and SWAN, the wave direction is considered, as well as the spectral distribution. Consistent results give confidence in both radar data and SWAN results. In general, the radar data seems to be reliable. An exception on this are regions with large bed gradients and small wave heights. At many locations, the wave spectra turn out to be bimodal. This makes it difficult to catch the wave direction in one value. In these cases, it is better to consider the full 2d spectra. The study has given insight into the quality and usefulness of the radar data. The radar observations provide an interesting data source, in addition to buoy data. Based on the first experiences with the radar data we believe that in the future the radar will be a reliable source for spatial wave data, providing proper insight in the wave models being applied in a complex area like the tidal inlet of Ameland. This will improve the prediction of extreme current and wave conditions in the Wadden Sea and thus decrease uncertainties in the safety assessments of our flood defense structures.

Keywords


X-band radar; remote sensing; SWAN; wave observations; Wadden Sea

References


Booij, N., R. C. Ris and L. H. Holthuijsen. 1999. A third generation wave model for coastal regions, Part I, Model description and validation, Journal of Geophysical Research, 104, C4, 7649-7666.http://dx.doi.org/10.1029/98JC02622

Deltares. 2010. Wave propagation under influence of currents. Deltares Report 1202119-003-HYE- 0002, 19 November 2010.

Eldeberky, Y. 1996. Nonlinear transformations of wave spectra in the nearshore zone, Ph.D Thesis, Fac. of Civil Engineering, Delft University of Technology, 203 pp.

Hasselmann, K., T. P. Barnett, E. Bouws, H. Carlson, D. E. Cartwright, K. Enke, J. A. Ewing, H. Gienapp, D. E. Hasselmann, P. Kruseman, A. Meerburg, O. Müller, D. J. Olbers, K. Richter, W. Sell, and H. Walden. 1973. Measurement of wind-wave growth and swell decay during the Joint North Sea Wave Project (JONSWAP), Dtsch. Hydrogr. Z. Suppl., A(8), 12, 95 pp.

Hasselmann, S., K. Hasselmann, J. A. Allender, and T. P. Barnett. 1985. Computations and parameterizations of the nonlinear energy transfer in a gravity-wave spectrum. Part 2: parameterization of the nonlinear transfer for application in wave models, Journal of Physical Oceanography 15, 1378-1391.http://dx.doi.org/10.1175/1520-0485(1985)015<1378:CAPOTN>2.0.CO;2

Van der Westhuysen, A.J. 2007. Advances in the spectral modelling of wind waves in the nearshore, Ph.D Thesis, Fac. of Civil Engineering, Delft University of Technology.

Van der Westhuysen, A.J. 2009. Modelling of depth-induced wave breaking over sloping and horizontal beds. Proceedings of 11th Int. Workshop on Wave Hindcasting and Forecasting.

Van der Westhuysen, A.J. 2010. Modelling of depth-induced wave breaking under finith-depth wave growth conditions, Journal of Geophysical Research, 115, C01008 doi:10.1029/2009JC005433.http://dx.doi.org/10.1029/2009JC005433

Van der Westhuysen, A.J., A.R. van Dongeren, J. Groeneweg, G.Ph. van Vledder, H. Peters, C. Gautier, J.C.C. van Nieuwkoop. 2012. Improvements in spectral wave modeling in tidal inlet seas, Journal of Geophysical Research, Vol. 117, C00J28, doi:10.1029/2011JC007837.http://dx.doi.org/10.1029/2011JC007837

Van der Westhuysen, A.J. 2012. Spectral modeling of wave dissipation on negative current gradients, Journal of Coastal Engineering, 68 (2012) 17-30.http://dx.doi.org/10.1016/j.coastaleng.2012.05.001

Witteveen+Bos. 2010. Analysis of SWAN underpredictions of offshore wave buoys AZB11 and AZB12, Report DT328-1/rijm3/012, 14 July 2010.

Zijderveld, A. and H. Peters. 2008. Measurement programme Dutch Wadden Sea, Proceedings of 31st International Conference on Coastal Engineering, 404-410.


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