2024-11-10T23:42:53Z
https://ir.soken.ac.jp/oai
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2023-06-20T15:51:02Z
2:429:18
Tidal gravity measurements corrected by recent global ocean tide models at five SG stations and the estimation of FCR parameters using Bayesian method
Tidal gravity measurements corrected by recent global ocean tide models at five SG stations and the estimation of FCR parameters using Bayesian method
KIM , TAEHEE
キム , テヒ
KIM , Taehee
We performed a validation study of six ocean tide models (CSR4.0, GOT99.2b, NAO.99b, FES2004, TPXO7.1, and TPXO7.2) using superconducting gravity data recorded at Syowa Station. From comparison with the observed loading effects, the most optimum ocean tide model was found to be TPXO7.2, which had a combined root mean square (RMS) misfit of 0.194 μGal for the eight major (four diurnal and four semidiurnal) waves. The next best ocean tide model was NAO.99b, with a combined misfit of 0.277 μGal. To determine the effect of inclusion of regional tide gauge and bottom-pressure data around Syowa Station, we estimated the combined RMS error for all eight waves; incorporation of these regional data into the TPXO7.2 model resulted in a 5% reduction in the misfit. Our phase lag anomalies indicated that the scatter of the out-phase component was greater than that of the in-phase component in the final residuals; this tendency was especially clear for O1, K1 and M2 waves. Improvement of the phase differences was the key to determine the optimum ocean tide model.<br/> We also used superconducting gravimeter data from four other stations in Metsahovi, Strasbourg, Sutherland and Canberra. For correction of the ocean loading effect, CSR4.0, GOT99.2b, NAO.99b, FES2004 and TPXO7.2 global ocean tide models were used. For the model that gave the smallest combined misfit, TPXO7.2, NAO.99b, TPXO7.2, CSR4.0 and TPXO7.2 were selected as the optimal ocean tide model at each station. TPXO7.2 gave the smallest combined misfit of diurnal bands at all stations.<br/>Comparing FES2004 and TPXO7.2, the imaginary component of the residual reduced for O1, K1 and M2 at TPXO7.2, while there still remained a relatively large imaginary component of the residual for S2, especially in the cases of Canberra and Syowa.<br/> In validation of theoretical values of elasticity/inelasticity, Strasbourg and Canberra stations gave values for K1 close to the inelastic theoretical value regardless of the ocean tide model. Sutherland recorded a gravimetric factor that was a little higher than the theoretical value, and Metsahovi and Syowa had large anomalous differences among ocean tide models. However, we could find the value obtained using the optimal ocean tide model was close to the theoretical inelastic value. it was skeptical to assert of verification of the latitude dependence of the tidal response yet, because of the inaccurate ocean loading correction for Metsahovi and Syowa. However, when considering the gravimetric factor corrected by new optimal ocean tide model is approaching to the theoretical value by Dehant et al., (1999), there is possibility to validate the discussion on latitude dependence. Applying a new calibration factor for Metsahovi reduced the real component error of the final residuals and gravimetric factors.<br/> Gravity data recorded by superconducting gravimeters at Metsahovi, Strasbourg, Sutherland, Canberra and Syowa stations were used to estimate the parameters of fluid core resonance (FCR) using the Bayesian method. From a statistical test on the imaginary component error in K1, 1 and 1 waves, increasing the percentage error in each wave separately, we found that the 1 wave was more sensitive to the correlation between the quality factor and imaginary component of the resonance strength and to the standard deviation of quality factor. The ocean loading effect was estimated using TPXO7.2, which gave the smallest combined misfit for each station in diurnal bands.<br/>In the estimation of FCR parameters using data from each station, the quality factor of Metsahovi, Sutherland and Syowa stations were found to diverge, i.e., non-symmetric probability density function (PDF). The result for quality factor at Strasbourg and Canberra showed the symmetric PDF and the most probable value by integration were 37762±4452and 3311±607 at each stations, respectively. <br/> Strasbourg was the only station which showed the correlation between quality factor and imaginary part of resonance strength. Metsahovi and Strasbourg had the value of 430±5 and 429±2 days, respectively for eigenperiod (T), these results are close to the theoretical result, 430 days (Mathews et al., 2002) within the margin of error. However, the result of 435±8, 432±6 and 433±43 days of Sutherland, Canberra and Syowa were large anomalous due to the noisy gravimetric factor of real part of K1 and 1.<br/> Employing the stacking method, the parameters of FCR were found to have a normally distributed probability density function. The values for parameters were 432±2days for the eigenperiod, 0.6362±0.006˚/h for the real component of resonance strength, -0.1967±0.0236˚/h for the imaginary component of resonance strength, and 35897±4230 for the quality factor.<br/>
総研大甲第1423号
jpn
thesis
https://ir.soken.ac.jp/records/2480
博士（理学）
2011-03-24
総合研究大学院大学
https://ir.soken.ac.jp/record/2480/files/甲1423_要旨.pdf
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2016-02-17