Plane wave fitting of the internal tidal sea-surface height signatures extracted from the TOPEX/Poseidon altimeter data
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Plane wave fitting of the internal tidal sea-surface height signatures extracted from the TOPEX/Poseidon altimeter data along satellite tracks CHEN Haibo1 , LV Xianqing1∗ , WANG Bin1 1
Laboratory of Physical Oceanography, Ocean University of China, Qingdao 266100, China
Received 31 December 2011; accepted 29 March 2012 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2012
Abstract The sea-surface height (SSH) signatures of internal tides extracted from the TOPEX/Poseidon (T/P) altimeter data along satellite tracks are fitted with superposition of several plane waves which have different wavenumber vectors. The key problem of plane wave fitting with iterative method is how to determine the initial value of wavenumber of each plane wave. The previous solving method is to analyze the internal tidal SSH signatures along each track with wavenumber spectrum. But it is found that the problem cannot be solved completely with the wavenumber spectrum analysis method only. The method based on the combination of wavenumber spectrum analysis method and the exhaustive method is proposed to determine the initial values of wavenumbers for iteration. Numerical results indicate that the proposed method is not only reasonable and feasible but also better than the previous method. The proposed method is an improvement of the previous one, which is beneficial to improving the precision of plane wave fitting of the T/P internal tidal SSH signatures and deepening the understanding of the internal tides in ocean. Key words: plane wave fitting, internal tides, TOPEX/Poseidon altimeter data
(Ray and Cartwright, 2001; Dushaw, 2002; Chiswell, 2006; Tian et al., 2003, 2006). Altimetric detection techniques may represent a great improvement over moored measurements owing to the near-global coverage of the satellites. With the propagation directions of internal tides known, we can continue our numerical study of internal tides with the theories of Baines (1982). Therefore, as a preliminary work, the plane wave fitting of the T/P internal tidal SSH signatures is an important link of the study of internal tides. Ray and Cartwright (2001) studied the internal tides near the Hawaiian Ridge by superposition of two waves radiating in two reverse directions and proposed the method for plane wave fitting of T/P along-track internal tidal signatures. Based on the method used by Ray and Cartwright (2001), Zhao and Alford (2009) made an improvement allowing two waves of arbitrary direction rather than requiring them to be in opposite directions. In the study of Zhao and Alford (2009), a least squares model is solved for a plane wave propagating in a certain direction, and the model is evalu-
1 Introduction As a ubiquitous phenomenon in the ocean, the internal tide, i.e., the internal wave of tidal frequency, is one of the most important sources of mechanical energy for mixing in the ocean (Munk and Wunsch, 1998). The internal tides have a remarkable contribution to dissipation of global ocean energy (Egbert and Ray, 2000; Rudnick et
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