Determination of the Earth’s Zonal Response in Length-of-day Variation to the Long-period Tides

• Main Authors: Tsung-Jung Shih, 施宗融
• Other Authors: 趙丰
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/48971881582520107562

碩士 === 國立臺灣大學 === 海洋研究所 === 100 === We estimate the Earth’s zonal tidal response coefficient κ from modern observed length-of-day (LOD) data for the period 1977-2009. Its magnitude and phase of κ contain important information about the Earth’s internal structure and dynamics. The influence of the atmospheric angular momentum (AAM) is firstly removed from the LOD data in order to better reveal the signals of long-period tides of periods ranging from 5 to 35 days. Numerical estimates of κ magnitude and phase lag are then obtained for 11 tides with sufficiently high signal to noise ratio (SNR). These estimates are compared with the theoretical baseline value, κ = 0.315, which is the value for a spherically symmetric Earth model under the additional assumptions of equilibrium long-period ocean tides and complete decoupling of the fluid core from the mantle. Comparison of our results with theoretical model computations is discussed in terms of possible frequency dependence of κ. Our κ amplitude and phase estimates are found to be consistent with two non-equilibrium ocean tide models, which are assimilated with precise sea surface height measurements provided by TOPEX/Poseidon satellite mission.