利用TOPEX/POSEIDON人造衛星測高儀測高資料偵測西太平洋海水面變化

Abstract

國外自1973年即應用人造衛星測高儀測高資料從事海洋研究，其範圍包括 潮汐變化、海水面變化、海水位變遷、地轉流及海洋地質等方面。台灣四 面環海，東岸位於太平洋西側，為黑潮必經之路線，因而，可借助衛星測 高儀之測高資料獲取迅速、資料點密集 (沿軌跡方向)等特性，研究大規 模的西太平洋海水面變化。 1992年8月，美國及法國太空總署合作發射載 有新一代測高儀之人造衛星TOPEX/POSEIDON，其軌道及測距精度皆優於過 去之人造衛星測高儀，再配合各種地球物理改正，其實用性大為提昇。因 此，我們嘗試應用衛星測高資料，著手研究西太平洋海水面之變化。本文 以TOPEX/POSEIDON人造衛星自1992年9月至1993年9月之測高資料，配合其 提供的各種改正量，從事海水面變化及海水位變遷之研究。我們將測高資 料經區域軌道及區域潮汐改正，應用1°x 1°平均值法和內插法，研究基 隆、台中、安平及富岡各驗潮站之海水位變遷。同樣地，測高資料經由區 域軌道改正以GMT軟体製成曲面，分析西太平洋海水面季節變化的情形。 由上述的研究方式，得知黑潮於夏季時強度最強，冬季最弱，而基隆及富 岡站海水位變遷趨勢的監測，衛星與驗潮資料相關係數達0.7以上。 Satellite altimetry has been used for the studies of ocean tides , sea surface variability , sea level change, geostrophic current and seafloor topography since 1973. TOPEX/POSEIDON , launched in August 1992,is a satellite mission that carries a precise rader altimeter system,and is jointly conducted by the NASA and the CNES. The precisions of its orbit and range measurement are better than any other satellites equipped with altimeters. Using TOPEX/POSEIDON altimeter data , we have analyzed the sea surface variability of the West Pacific Ocean and sea level change around Taiwan from September 1992 to September 1993. In this study , we do local orbit and local tide corrections for altimeter data.The sea level changes were investigated at the tide gauge stations of Keelung , Taichung , Anping and Fukan by interpolation and 1°x 1° average methods. Also,we use GMT software to surface altimeter data to analyze the sea surface variability of the West Pacific Ocean. The results show that the Kuroshio currents has a minimum magnitude in winter and a maximum extent in summer. Thetimeter measurements were validated against in situ sea levelsurements at Keelung and Fukan. The comparison between thelevel variations from TOPEX/POSEIDON and tide gauge data yields a correlation coefficient as high as 0.7.