衛星測高資料處理增益全球海洋重力場精度

Abstract

藉由更新Seasat，Geosat，ERS-1，ERS-2及TOPEX/POSEIDON五種交大衛星資料庫以期增進全球海洋重力異常精度。新版的Geosat/GM及Geosat/ERM JGM3 GDR數據取代了舊的T2 GDR數據，且較舊的數據擁有更好的物理改正模式。除了Seasat及T/P之外，將海潮改正模式更新為NAO99b。對重複週期任務有新的剔除粗差方法及平均海水面高的方法。對非重複週期任務的標準偏差給定有較嚴密之方式，但我們得到的結論是使用經驗方式給定非重複軌道任務的標準偏差能使本文重力和船測重力的差異最小。對於衛星資料平滑處理率波波長之給定吾人也是依據經驗法則來決定。 最後，使用逆Vening-Meinesz公式配合1D FFT的計算方法在12個全球海洋測試區域求出其重力異常。而其南北、東西分量網格的組成是使用最小二乘配置法（LSC）。本文所求的海洋重力異常與Hwang et al.（1998）相較精度平均提升了約0.77mgal。

The altimeter database at the National Chiao Tung University, which includes data from Seasat, Geosat, ERS-1, ERS-2 and TOPEX/POSEIDON missions, is updated in this study in an attempt to derive marine gravity with an improved accuracy. The old Geosat/ERM and Geosat/GM are replaced by the JGM3 GDRS, which use better geophysical correction models compared to the previous version. For the tide model except for Seasat and T/P, the NAO99b model is used. A new method is used to remove outliers and compute averaged sea surface heights for the repeat missions. A more rigorous method of assigning standard deviations to the non-repeat missions is studied, but we conclude that an empirical standard deviation for each of the non-repeat mission will yield a better agreement between computed gravity anomalies and shipborne values. The optimum filter wavelengths for the altimeter data for the non-repeat missions are also empirically determined. Finally the inverse Vening Meinesz formula with the 1D FFT technique is used to compute gravity anomalies at 12 areas in the world ocean. Gridding of north and east components is done by least-squares collocation. On average the accuracy of the derived marine gravity anomalies is improved by 0.77 mgal compared to those of Hwang et al. (1998).