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/POSEIDON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網 格,再使用逆Vening Meinesz公式的1D FFT計算技巧,計算得全球2'x2'的網格重力異常.計 算成果含括範圍, 經度由0度至360度 ,緯度由南緯72度至北緯72度 . 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∼10 mgals. 此外, 本文 重力與Sandwell 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勿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 式與重力成果將以起置於交大土木所測量組的公共檔案傳輸伺服器(ftp server)中, 網址 為ftp://gps.cv.nctu.edu.tw, 歡迎各界使用與指教. Global marine gravity anomalies at a 2'x2'grid have been determined fromSe asat､Geosat､ERS-1 and TOPEX/POSEIDON altimeter data. The inverse VeningMeine sz formula with an 1D FFT method was used to compute gravity anomaliesfrom gri dded north-south and west-east geoid gradients, in a remove-restoreprocedure w ith the EGM96 gravity model as the reference field. The data coverthe area 0° to 360° in longitude and 72°S to 72°N in latitude. In the 12 test areas where ship gravity and satellite-derived gravitywere compared, rms agreements of 6-10 mgals were obtained and the gravityanomalies derived in this work are 0.5 mgal on average better than thosederived by Sandwell and Smith (1997). Th e gravity anomalies are locatedat an ftp site (ftp://gps.cv.nctu.edu.tw) where an application program isavailable for extracting data in a subarea.