A series of 40-year significant wave height (SWH) data were extracted from the ERA-Interim data set of the European Center for Medium-Range Weather Forecasts (ECMWF), for the Beibu Gulf and its adjacent waters in the South China Sea from 1979 to 2018. After that, data were first aggregated to annual and monthly average data. Through the analysis, the annual SWH had grown since 1984, reached a significant level in 1995, and reached a maximum 1.068 m in 2011. The monthly SWH values between April and September were lower than those of other months. Additionally, the corresponding analysis on wind speed data demonstrated that variation in wind speed was consistent with SWH from 1979 to 2018, but the overall trend of SWH increased while wind speed decreased. The decrease of wind speed could be attributed to the weakening of the East Asian monsoon, and the westward swell induced by the gales that occurred in the northeast of the South China Sea resulted in the increase of SWH in the study area. Finally, a multiple sine function decomposition neural network (MSFDNN) was employed to forecast monthly SWH over the next 10 years. The predicted results revealed that the MSFDNN was well-performing for forecasting monthly SWH.

南海北部湾有效波高的分析与预测

从欧洲中期天气预报中心(ECMWF)的再分析数据集，提取了1979-2018年北部湾及其邻近南海海域40年的有效波高(SWH)数据。之后，首先将数据汇总为年平均数据和月平均数据。通过分析，SWH1984年开始增长，1995年达到显著水平，2011年达到最大值1.068 米。四月至九月的月SWH较其他月份较低。此外，对相应的风速数据分析表明，1979-2018年风速的变化与SWH变化一致，但SWH的总体趋势是增加的而风速的总体趋势是减少的。风速的减小可能与东亚季风减弱有关，南海东北部大风引起的向西扩散导致研究区SWH增加。最后，利用多正弦函数分解神经网络(MSFDNN)对未来10年的月SWH进行预测。预测结果表明，MSFDNN对月SWH有较好的预测效果。