A grey model with periodic term for sea-level analysis and its application to Guangxi coast

A grey model with periodic term for sea-level analysis is presented in this paper.The present model remains some advantages of (UM (1,1)model,which well reflects the trend of sea-level changes and gives out the change rate as well as acceleration of sea level conveniently.In addition, the present model can reproduce the periodic phenomenons of sea level, hence, it overcomes the shortcomings of GM (1,1)model that is unsuitable for forecasting monthly mean sea level with apparent periodicity,and the prediction accuracy is improved.The present model is used to analyse Guangxi coast sea level, the results show that, the rise rates of relative sea level at Beihai, Weizhou and I3ailongwei are respectively 1.67, 2.51 and 0.89 mm/a, the relative sea level at Shitoubu has a faVing trend, the fall rate is 0.5~1.0 mm/a, the rise rate of eustatic sea level along Guangxt coast is 2.0 mmia.In comparison with the model of linear trend term plus periodic term, the simulation accuracies of both models are equivalent.