Observations of Typhoon Waves in a Reef Lagoon of the South China Sea

Abstract

Based on wave measurements lasting three and a half years, typhoon wave characteristics in a lagoon of the South China Sea are discussed in this paper. According to the upper boundaries of wind speed and significant wave height Hs, the maximum wave height has a similar rate of change as the maximum wind speed. The peak frequencies decrease in the approaching stage and are concentrated with an average of 0.1415 Hz in the leaving stage. The distributions of the wind and wave directions indicate that the local wind waves and the waves from the open sea propagated to the site in the approaching and leaving stages, respectively. Wind waves generated inside the lagoon are fetch-trapped, and the spectra can be described by αf(−4) or βk(−2.5) when f > fp. In addition, the measurements show that the nondimensional maximum spectrum can be estimated by the nondimensional fetch. The spectra of the waves from the open sea can be described by afp⁡(c−b)f⁡(b). Parameters a and c are determined by the nondimensional peak frequency. In addition, it is found that the peak energy density S(fp) is a linear function of g−1/2Hs5/2 for all waves.

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

“…Although the Xisha Islands comprise the biggest archipelago in the Northern South China Sea, they only occupy a very small part of the map. Observation data and numerical hindcast data are rarely reported in this region [19,20]. The wave conditions at the Xisha Islands are mainly affected by swells from distant storms in the South China Sea and young waves generated by winds passing through the islands [21].…”