結合Seasat、Geosat、ERS-1和TOPEX/POSEIDON衛星測高資料計算全球海洋重力異常

Abstract

本文為結合Seasat、Geosat、ERS-1和TOPEX/P0SEIDON四顆衛星六種測高資料來計算全球海洋重力異常。計算方法採去除回復法（Remove-Restore Method），應用的參考大地位模式為EGM96。計算重力異常時，先將海水面高度組成南北、東西分量的殘餘大地梯度网格，再使用逆Vening Meinesz公式的1D FFT計算技巧，計算得全球2'×2'的网格重力異常。計算成果含括範圍，經度由0°至360°，緯度由南緯72°至北緯72°。 這項成果在全球12個測試區域中與平差後船測重力較差的均方根值（rms）平均約6~10mgals。此外，本文重力與Sandwe11 and Smith 於1996年所發表的7.2版全球海洋重力異常比較，本文重力精度優於Sandwell and Smith 重力約0.5mgals。這項成果提供了地球物理相關領域高解析度的海洋重力訊息。為方便使用者擷取所需範圍之重力資料，本文附有一應用程式，這個程式與重力成果將一起置於交大土木所測量組的公共檔案傳輸伺服器（ftp server）中，址為ftp://gps.cv.nctu.edu.tw，歡迎各界使用與指教。

Global marine gravity anomalie at a 2'×2' grid have been determined from Seasat, Geosat, ERS-1 and TOPEX/POSEIDON altimeter data. The inverse Vening Meinesz formula with an 1D FFT method was used to compute gravity anomalies from gridded north-south and west-east geoid gradients, in a remove-restore procedure with the EGM96 gravity model as the reference field. The data cover the area 72°S to 72°N in latitude and 0° to 360° in iongitude. In the 12 test areas where ship gravity and satellite-derived gravity were compared, rms agreenents of 6-10 mgals were obtained and the gravity anomalies derived in this work are 0.5 mgal on average better than those derived by Sandwell and Smith (1997). The gravity anomalies are located at an ftp site (ftp://gps. cv.nctu.edu.tw) where an application grogram is available for extracting data in a subarea.