Abstract
This paper describes long-term spatiotemporal trends in extreme significant wave height (SWH) in the South China Sea (SCS) based on 30-year wave hindcast. High-resolution reanalysis wind field data sets are employed to drive a spectral wave model WAVEWATCH III™ (WW3). The wave hindcast information is validated using altimeter wave information (Topex/Poseidon). The model performance is satisfactory. Subsequently, the trends in yearly/seasonal/monthly mean extreme SWH are analyzed. Results showed that trends greater than 0.05 m yr−1are distributed over a large part of the central SCS. During winter, strong positive trends (0.07–0.08 m yr−1) are found in the extreme northeast SCS. Significant trends greater than 0.01 m yr−1are distributed over most parts of the central SCS in spring. In summer, significant increasing trends (0.01–0.05 m yr−1) are distributed over most regions below latitude 16°N. During autumn, strong positive trends between 0.02 and 0.08 m yr−1are found in small regions above latitude 12°N. Increasing positive trends are found to be generally significant in the central SCS in December, February, March, and July. Furthermore, temporal trend analysis showed that the extreme SWH exhibits a significant increasing trend of 0.011 m yr−1. The extreme SWH exhibits the strongest increasing trend of 0.03 m yr−1in winter and showed a decreasing trend of −0.0098 m yr−1in autumn.
Highlights
Wave climatology has been traditionally based on buoy measurements and ship observations
A comparison of linear trends in the annual averages of the “winter” and “summer” significant wave heights over a 31-year period by three National Data Buoy Center (NDBC) buoys which are buoys 44004East of Cape May, NJ, 41001-East of Cape Hatteras, NC, and 41002-East of Charleston, SC, all in the US East Coast [29] with the trends in the annual averages of the “winter” and “summer” significant wave heights obtained in this study showed that, in the South China Sea (SCS), winter exhibits a higher trend (0.0076 m yr−1) in wave height than the trends obtained for the 3 Atlantic buoys which are, respectively, −0.002, 0.001, and 0.002 m yr−1
A 30-year wave simulation for the SCS based on highresolution reanalysis wind field data sets is presented in this study
Summary
Wave climatology has been traditionally based on buoy measurements and ship observations. The former provide accurate but spatially scarce information on wave parameters, whereas the latter provide limited spatiotemporal coverage during extreme conditions [1]. These are still quite inadequate to estimate long-term trends in ocean wave parameters. Wave modeling (hindcasting) is one of the major sources of wave data that gives high-resolution (spatial and temporal) long-term wave information in areas sparsely covered with buoy measurements. Wave modeling excellence strongly depends on accurate wind fields covering the study area and the simulation period. Long-term changes in wave characteristics can modify the profile of the coast and the shape of sandy beaches through changes in nearshore circulation and sediment transport characteristics [2, 3]
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