The Research Of Effect And Model Refinement Of Ocean Tide Loading

Ocean tide is caused by the solar-lunar tide-generating force effect of the earth, soocean tide loads have an influence on the observations of geophysical fields and the influencelevel can reach centimeter-level. With the continuous development of observationtechnologies and its extensive applications, people has a higher requirement on the accuracyof observation results, therefore the influences caused by ocean tide loads cannot be ignoredand it is necessary to establish the corresponding model to take off ocean tide loads. Based onthis, this paper carried out a series of theory of ocean loading tides and the elaborationresearch of the models. In this paper, the research contents mainly included two parts. On onehand, we studied the ocean tide load’s influence and the law on the geophysical field,involving the theory of ocean loading effects and correction models of ocean tide load. Basedon global the ocean tide model, we got the influences of GPS precise positioning, gravity, tiltand strain field which were caused by ocean tide loads. On the other hand, using a modelobtained by offshore tide station data to replace the corresponding areas of the global oceanmodels were studied in order to achieve the refinement of the global ocean tide models. Themain content of this paper is as follows:(1) This article describes the basic principles of ocean tide loading. And also introduces theelasticity theory and Green’s function, which are used to calculate the loading correction.On this basis, this paper study the correction model of the ocean tide loading. Also studythe effect on the displacement of station and GPS baselines from the ocean tide loading.The search results shows that the effects on the displacement of station can reach atcentimetre-level in the coastal region. It is4-5times of inland stations. It is greater thaninland area. The influence of the ocean tide loading on the horizontal direction is the2-3times of elevation direction. In addition, the influence of ocean tide loading on the GPSbaseline reach at millimeter-level. It is related to the azimuth Angle of the baseline and thesize of the load on the two stations.(2) The diffences between ocean tide loading models has analyzed and we also got theconclusion that the difference between FES2004and NAO99b ocean tide loading models is small in inland,but in coastal areas the difference is bigger,because the influence ofocean tide loading in coastal areas is big.So it is important to select the appropriate modelfor GPS。(3) The paper studied the effect of ocean tide loading on gravity, tilt and strain,and hasobtained that effect on gravity which changed in half moon cycle. The effect is related tothe location of station. Ocean tide loading effect on gravity, tilt and strain in coastal areasis bigger than inland.(4) We used high-accuracy local model to revise global ocean tide model,compared thedifference between revised and unrevised ocean tide model in gravity, tilt, strain anddisplacement.The result shows the difference is increasing with the decrease of thedistance from the sea and correction effect of revised ocean tide model is better thanunrevised ocean tide model.(5) Based on elevation and Zenith delay value of station,we selected and compared ocean tidemodels.In addition,we studied the relationship between elevation and Zenith delay valueof ocean tide loading effect.Compared the result of GPS observation and modeled value inorder to selected the better ocean tide model. And we got the conclusion that the effect ofocean tide loading on Zenith delay value has a linear relationship with ocean tide loadingon elvation of station.(6) Explores the theory of techniques and methods through GPS observation data to estimatethe ocean models, using GPS differential technique and PPP to estimate the ocean modelsrespectively, obtained the conclusion of using long time series of GPS to estimate theocean models can be better.