NHESS Natural Hazards and Earth System Sciences NHESS Nat. Hazards Earth Syst. Sci. 1684-9981 Copernicus Publications Göttingen, Germany 10.5194/nhess-14-73-2014 Assimilation of decomposed in situ directional wave spectra into a numerical wave model of typhoon waves Fan Y. M. 1 Günther H. 2 Kao C. C. 3 Lee B. C. 4 Coastal Ocean Monitoring Center, National Cheng Kung University, Tainan, Taiwan Institute of Coastal Research, Helmholtz-Zentrum Geesthacht Centre, Geesthacht, Germany Department of Hydraulic & Ocean Engineering, National Cheng Kung University, Tainan, Taiwan Department of Environmental and Hazards-Resistant Design, Huafan University, Taipei, Taiwan 09 01 2014 14 1 73 80 Copyright: © 2014 Y. M. Fan et al. 2014 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://nhess.copernicus.org/articles/14/73/2014/nhess-14-73-2014.html The full text article is available as a PDF file from https://nhess.copernicus.org/articles/14/73/2014/nhess-14-73-2014.pdf

The purpose of this study was to enhance the accuracy of numerical wave forecasts through data assimilation during typhoon periods. A sequential data assimilation scheme was modified to enable its use with partitions of directional wave spectra. The performance of the system was investigated with respect to operational applications, specifically for typhoon waves. Two typhoons that occurred in 2006 around Taiwan (Kaemi and Shanshan) were used for this case study. The proposed data assimilation method increased the forecast accuracy in terms of wave parameters, such as wave height and period. After assimilation, the shapes of directional spectra were much closer to those reported from independent observations.

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