Establishment Of Mean Sea Surface Models And Prediction Of Sea Level Changes Over Sea Of Japan And Its Adjacent Ocean Based On Satellite Altimetry,Tide Gauge And GNSS

Mean sea surface(MSS)is the basic element of the earth system,and also the datum level of geoid and watershed erosion,which can be used to study the earth shape,geoid,gravity field model and other issues.In addition,the determination and prediction of the MSS is an important content of geodesy and physical oceanography research.The reference datum in geodesy and hydrographic surveys all use the MSS or a reference surface with a certain relationship with the MSS.There are two research foci in this paper:the establishment of MSS model and prediction of sea level change.The MSS model is an important reference for the study of chart datum and sea level change,and the coastal accuracy of the model is always the focus of geophysics and oceanography.Sea level change is also the research hotspot of global concern,especially sea level changes in offshore areas.Hence the prediction of which in offshore areas is particularly important.Based on satellite altimetry data from 1993 to 2018,the MSS model(referred to as Altimetry Japan MSS)with a grid of 1'×1' over sea of Japan and its adjacent ocean(25°N?50°N,125°E?150°E)was established by the 19-year moving average method.The exact repeat mission data of all satellites in this model are adjusted by the collinear adjustment,and the sea level variations in geodetic mission data are corrected.Then,the single-satellite and multi-satellite altimeter data are adjusted by the crossover adjustment successively.Last,the Altimetry Japan MSS is obtained by using the least square collocation method.Different from the latest international MSS models CLS15 and DTU18,the measured data of the latest altimetry satellites HY-2A,Janson-3 and Sentinel-3A are also introduced into the Altimetry Japan MSS.The STD of the difference between the Altimetry Japan MSS and CLS11,WHU13,CLS15 and DTU18 models decreases with the increace of the distance from the coastline,and the largest reduction is in the rang of 10 to 20 km from the coastline.The STD is stable after 40 km,which is about 0.025 m.In order to improve the offshore accuracy of Altimetry Japan MSS,the 24 tide gauge stations and the joint GNSS along the coast of Japan are used to correct the SSH within 10 km from the coastline by using the Gaussian inverse distance weighting method and the MSS model with higher offshore accuracy(referred to as Japan MSS)is obtained.The comparison of SSH difference between Japan MSS,CLS 15,DTU 18 and the four tide gauge stations(not used during correction.)along the coast of Japan shows that the coastal accuracy of Japan MSS is better than CLS 15 and DTU18,and the difference between Japan MSS and the four tide gauge stations is 2?3cm.Furthermore,the comparison and analysis of the SSH anomaly calculated by SARAL,HY-2A,Sentinel-3B and other satellites with that of Japan MSS,DTU18,CLS 15,CLS11,and WHU13 models within wavelength 35?300 km,it can be seen that,Japan MSS has the smallest error and its accuracy is relatively reliable.A new sea level change prediction method proposed in this paper is SSA +ARMA.Firstly,SSA is used topredict the principal components of time series,and takes the remaning sequence after deducing the principal component as a random sequence.Then the ARMA model is used to predict it by extrapolation.The result of SSA principal component prediction plus ARMA extrapolation is the final prediction result of SSA+ARMA.Based on the tide gauge record and joint GPS data along the coast of Japan,the relative sea level change,absolute sea level change and vertical crustal change in 2014-2018 are predicted with SSA and SSA+ARMA.The verification is carried out with the actual measured value of tide gauge and GPS at the same time.The results indicate that accuracies of relative sea level,vertical crustal motion and absolute sea level predicted with SSA+ARMA,which are better than those predicted by SSA only.Among them,the prediction accuracy of SSA+ARMA is 4?6cm within 5 years of absolute sea level.Based on that,The SSA+ARMA is used to predict the absolute sea level change in the coast of Japan from 2019 to 2023.The results show that the average sea level height in 2019-2023 is 35.25mm higher than that in previous years(2014-2018),and the change rate of absolute sea level in 2003-2023 is 3.86mm/yr.The prediction result is reliable.Therefore,the SSA+ARMA combined prediction model provides an effective and feasible reference and example for the study of sea level change prediction.