ZHAO30yr: An Internal Tide Model Based on 30 Years of Satellite Sea Surface Height Measurements

ZHAO30yr is an internal tide model developed using 30 years of satellite sea surface height (SSH) measurements from 1993 to 2022 by a newly improved mapping technique. The model is evaluated by making internal tide correction to independent altimetry data in 2023. ZHAO30yr performs much better than ZHAO20yr, a model developed using 20 years of data by an obsolete mapping technique. ZHAO30yr is a fruit of 30 years of satellite altimetry operation by the international satellite altimetry community. The model may find its applications in a wide variety of scientific research and practice. ZHAO30yr is a new-generation model, because it decomposes the internal tide field and reveals numerous long-range internal tidal beams, which contain key information on their generation, propagation, and dissipation. In contrast, all previous empirical internal tide models only give the multiwave summed amplitudes and phases (Carrere et al. 2021).The model has the following outstanding features:ZHAO30yr provides model errors that are estimated by background internal tides. The combination of new mapping technique and long data record reduces model errors down to lower than 1 mm; therefore, we can extract the much weaker minor and mode-2 internal tide constituents;ZHAO30yr contains 12 internal tide constituents: 8 mode-1 constituents (M₂, S₂, N₂, K₂, K₁, O₁, P₁, and Q₁) and 4 mode-2 constituents (M₂, S₂, K₁, and O₁). It has more constituents than all previous empirical internal tide models published in Carrere et al. (2021, Table 1);ZHAO30yr resolves the 12 internal tide constituents each by 5-wave decomposition. It thus decomposes the global multiconstituent multimodal multidirectional internal tide field into 60 simple plane waves at each grid point. The decomposition gives many new features that are previously masked by multiwave interference; andZHAO30yr contains directionally decomposed components, which reveal numerous well-defined long-range internal tidal beams associated with notable topographic features. The beams are characterized by large amplitudes, linear-increasing phases, and across-beam co-phase lines.In this folder, there are 12 internal tide constituents given by 12 separate mat files. Each file contains three types of internal tide products: (1) SSH and phase are the multiwave summed internal tide field; (2) IW1-IW5 are the 5 waves at each grid point decomposed by plane wave analysis; and (3) directionally-decomposed components are labeled southmax, northmax, westmax, and eastmax. Figures show the decomposed components and isolated internal tidal beams. Model errors are saved in a separate mat file. Researchers are encouraged to use the new model in their research. Please contact Dr. Zhongxiang Zhao ([e-mail]) for your research plans or questions you might have.Carrere, L., Arbic, B. K., Dushaw, B., Egbert, G. D., Erofeeva, S. Y., Lyard, F., Ray, R. D., Ubelmann, C., Zaron, E., Zhao, Z., Shriver, J. F., Buijsman, M. C., and Picot, N. (2021): Accuracy assessment of global internal tide models using satellite altimetry, Ocean Science, 17, 147–180. https://doi.org/10.5194/os-17-147-2021.