基于SSA和MGF的海面变化长期预测及对比

Long-term prediction and comparison of sea-level change based on the SSA and MGF model

海面变化预测受到建模思路、方法选择、数据长度及数据质量等因素的影响,导致了海面变化预测的不确定性。本文以国内6个验潮站自20世纪50年代以来的月平均潮位序列为基础,采用奇异谱分析(SSA)与均值生成函数(MGF)模型相结合的方案,以各站位最初20余年数据为基础建立预测模型,以后续年份的实测数据进行了多方案对比验证及检验。预测试验显示MGF模型具有较高的预测精度,并表现出较好的长期预测的稳定性特点。以SSA去噪序列为基础,应用MGF模型预测了各站位至2050年的月尺度海面值,年均值计算结果表明至2050年海面波动上升的幅度不超过20cm,海面变化速率同样表现出阶段性和波动性。与前人相关研究成果对比表明,本文所采用的SSA与MGF相结合的预测结果具有可比性,在方法原理和验证结果上看具有较好的长期预测潜力。

Tide gauges and satellite altimetry are the two measurements techniques of present-day sea level change, and tide gauges provide sea-level variations with respect to the land on which they lie. The predictions of sea-level changes are affected by modeling, methods, data length, data quality and other factors, which cause the uncertainties of prediction. Based on the monthly average tidal records of six tidal gauge stations in East China since the 1950s, Mean Generation Function（MGF） and Singular Spectrum Analysis （SSA） are employed to discuss the stability of long-term prediction. MGF model is built with each station＇s initial data of over 20 years, and the subsequent data are used to undertake comparative multi-experiments and tests. As a result, these prediction experiments testify that MGF exhibits more favorable and steady long-term prediction. Therefore, based on SSA denoised series, the MGF model is used to predict the sea-level changes of each station on the monthly scale till the year 2050. All stations take on obvious fluctuated rising trend. The calculated annual mean series indicate that the upper limit of the fluctuated sea-level changes can be no more than 20 cm. The velocity of the sea-level changes show periodity and fluctuant with prominent differences in the ascending and degressive segments accompanying with obviously spatial variation. Compared with the previous research findings, whose results are primarily done under linear hypothesis and may show limitation to some extent. Owing to the fluctuations and irregularities of sea-level chan- ges, the prediction conclusion adopted by SSA and MGF methods are relatively comparable, and have favorable long-term prediction potential in terms of methodology and experimental results. Natural forcing, which is a combination with anthropogenic forcing plays an important role in the sea-level change, and there are still enormous uncertainties about sea-level change and its prediction. The integrated prediction system should be constructed with the consideration of multiple factors. Furthermore, comprehensive and comparative research is also needed.