MOM4 Global Tidal Wave Simulation Study Based On

Based on the code of the Ocean General Circulation Model MOM4,we simulated global barotropic tide in medium and eddy-permithorizontal resolution. We explored the most appropriate model settingsand data preparations for the global tide modeling using MOM4, in orderto reduce the inordinately large energy in the model, both increasing thebottom drag coefficient and including an internal tide dissipation term isadopted, which prove to be helpful in improving the simulation.As for Z-coordinate ocean model, including of the bottom partial cellshelp to construct accurate model topography, compared with Full cells,the global tide results in Partial cells experiment are much better;Reducing vertical levels improves experiment efficiency, and resultsshow the global tide simulation is insensitive to the simplified verticallevels; Global tide simulation is quite sensitive to the model topographypreparation, the Blackman radial filter is adopted to filter theoriginal topo-data into the model grids, and the simulation result isreasonable only when the filter radius is twice the model grid distance.We compared the topo-data of Etopo1/2/5, to recognize the relativedeviation is18.7%between Etopo2and Etopo5, and5.5%between Etopo2and Etopo1, the deviation between Etopo2and5leads todiscrepancy of4.6cm in global M2results; Statistic analysis show that theresults in the eddy-permit horizontal resolution models are better thanthose in medium horizontal resolution models; The results in the mediumhorizontal resolution models is sensitive to the choosing of time step, andthe time step in the medium horizontal resolution models should notlarger than600s; The preliminary results in the8constituents runs showthat compared with TPXO7.2our model can reproduce most characteristics of global M2, S2, K1, O1tides, but the amplitude is larger,the global energy flux vector of M2is calculated, compared with theresults of TPXO7.2, our model results are reasonable in patterns butlarger in amplitude; In order to reduce model energy including an internaltide dissipation term is adopted, which do help to improve the modelresults significantly, the optimally tunedκis7.0e-4, the optimally tunedglobal M2RMS error is6.2cm. We calculated the global tide energydissipation in both cases, and the energy dissipation distributions in theruns with internal tide dissipation term are more close to the observations.Based on the simulation with horizontally uniform stratification, the stericSSH is diagnosed, results show that the low mode internal tide isgenerated at the ‘hot spots’(such as Hawaii) regions, and radiated awayfrom the generation sites, which is consistent with the previous study.