利用人造衛星測高儀資料改善西太平洋海潮模式

Abstract

海洋潮汐的估算與預報對於海洋研究、漁業亦或是軍事皆相當重要，在以 往僅靠岸邊之驗潮站來做點的評估，自從人造衛星測高儀發展後，海潮的 計算已可推展到整個海洋面。本文利用TOPEX/POSEIDON和ERS-1兩顆測高 儀資料解算M2分潮殘差量，以改善Texas大學Austin分校太空研究中心發 展的CSR3.0 Tide Model。研究區域包含整個西太平洋從北緯0°∼50°， 東經 100°∼150°，首先使用交叉點平差法降低徑向軌道誤差後，再利 用球諧分析法在海水面殘餘變化量中分離出M2分潮的殘差量振幅與相位。 所得之成果與13個地面驗潮資料做比較。以平均海水面當作海水面變化的 參考面，其平均海水面TOPEX/POSEIDON使用36個10天重複軌道週期的平均 值，而ERS-1使用18個35天重複軌道週期的平均值。應用上述之方法， ERS-1測高儀資料所得之成果比T/P測高儀好，而在地面軌跡夠密時使用20 階球諧展開之成果最佳，ERS-1資料及結合兩顆衛星之資料其平均均方根 皆改善了1.6公分，優於國外所做改善1.2公分。 The prediction of ocean tide is important for oceangraphic research and applications in the fishery and military. The conventional ground-based method has been largely dependent on tide gauge data and the prediction is done on a point-by-point basis. Since the development of satellite altimetry, it is ssible to predict ocean tide on a global scale and the area cover can be a continous two-dimensional surface. In this study, the residual M2 tide caculated fromPEX/POSEIDON(T/P) and ERS-1 altimeter data is used to improve Csr3.0 tidemodel which is developed by the Center of Space Research, University of Texas, Austin. Te studied area covers the Western Pacific, ranging from 0°∼50°north and 100°∼ 150°east. First, we use a crossover adjustment to reduce orbit errors. Then the residual M2 tide is determined from the residual sea surface height obtain by subtracting a mean sea surface from the sea surface from individual cycles. The caculation of residual M2 tide is based on the spherical harmonic expansions for amplitude and phase. harmonic expansions for amplitude and phase. The mean sea surface of T/P was constructed from 36 10-day repeat cycles, while 18 35-day repeat cycles were used for the ERS-1 mean sea surface The comparison using 13 tide gauge data shows that the results derived from ERS-1 alitmeter data are better than that from T/P altimeter data. Moreover, the best result is obtained when we use the spherical harmonic expansion to degree 20. The RMS error is reduced to 1.6 cm when we add the residual M2 tide to the CSR3.0 tide model This is better than the 1.2 cm improvement derived in other research institutions.