Extreme significant wave height of tropical cyclone waves in the South China Sea

Abstract

Abstract. Extreme significant wave heights are assessed in the South China Sea (SCS), as assessments of wave heights are crucial for coastal and offshore engineering. Two significant factors include the initial database and assessment method. The initial database is a basis for assessment, and the assessment method is used to extrapolate appropriate return-significant wave heights during a given period. In this study, a 40-year (1975–2014) hindcast of tropical cyclone waves is used to analyse the extreme significant wave height, employing the peak over threshold (POT) method with the generalized Pareto distribution (GPD) model. The peak exceedances over a sufficiently large value (i.e. threshold) are fitted; thus, the return-significant wave heights are highly dependent on the threshold. To determine a suitable threshold, the sensitivity of return-significant wave heights and the characteristics of tropical cyclone waves are studied. The sample distribution presents a separation that distinguishes the high sample from the low sample, and this separation is within the stable threshold range. Because the variation in return-significant wave heights in this range is generally small and the separation is objectively determined by the track and intensity of the tropical cyclone, the separation is selected as a suitable threshold for extracting the extreme sample in the tropical cyclone wave. The asymptotic tail approximation and estimation uncertainty show that the selection is reasonable.

Study on the Wind and Wave Environmental Conditions of the Xisha Islands in the South China Sea

“…Wind and wave data covering a sufficiently long time period can provide a statistical description of seasonal variations, as well as multi-year extreme conditions, for the appropriate design and operation of offshore structures. The long-term wind and wave characteristics have been widely investigated in the South China Sea, especially at some locations near the mainland [2][3][4][5][6][7]; however, due to a lack of observation data, the wind and wave environmental conditions of the Xisha Islands have rarely been investigated. Fortunately, numerical hindcast techniques for wind and ocean waves have been well-developed in recent years and validated in different engineering areas, including the Red Sea [8], the Baltic Sea [9][10][11], the Mediterranean Sea [12,13], the Adriatic Sea [14], the Black Sea [15], the south Atlantic Ocean [16], the Persian Gulf [17], and the Italian coast [18].…”

Study of Directional Declustering for Estimating Extreme Wave Heights in the Yellow Sea

“…An appropriate estimation of extreme waves plays an important role in protecting the coastal and ocean structures [1]. This estimation affects the design wave height [2], which implies a balance between the security and expenditure of structures [3]. In the engineering community, a large design value is likely to increase the engineering expenditure, but a small design value is unlikely to ensure the engineering security [4].…”