黑潮通量及其變化之觀測-子計畫：以超導重力、衛星重力及衛星測高研究氣候變遷對黑潮之衝擊

Abstract

超導重力儀為一整合性重力感測裝置，自2006年在新竹重力基準站設置，目前進行於陽明山衛星追蹤站設置另一台超導重力儀，並以1 Hz之取樣頻率獲得重力觀測量。超導重力儀可探測周圍環境因質量重新分佈而引起的微小重力變化，由於此主題中所涉及的黑潮訊號與環境噪訊比較起來相對微弱，故需發展環境因子之最佳模式，達到萃取海洋訊號之目的。 GRACE提供之全球重力場已廣泛應用於氣候變遷之相關議題，如監測海水質量在全球之變化狀況。由於目前GRACE空間解析度約為250~300公里，對於本計畫之研究區域而言其解析度不足，本計畫預計以區域解之方式提升西太平洋黑潮相關區域的重力異常空間解析度。 衛星測高技術提供研究區域之海面高，利用Geosat、ERS-1、ERS_2、ENVISAT、TOPEX/Poseidon、 Jason-1與Jason-2等測高資料分析近30年來研究區域之海水體積變動，探討與質量變化相關之特性。配合由歐洲太空總署提供之全球重力場GOCE，利用測高資料，以此大地起伏模式計算動力高。 本研究中，將致力發展黑潮區域與質量變化相關之特性，如黑潮之體積流量、黑潮路徑變化、海底壓力等其他物理特性，並分析氣候變遷指數CCI與北赤道流分歧點及黑潮參數變化之關係。

The superconducting gravimeter (SG) is a sensor that detects gravity change. Since 2006, a SG (T48) has been installed at Hsinchu. A new SG (T49) is to be installed at the GPS permanent s tracking station of Mt. Yangming satellite. SG collects gravity data at 1 Hz sampling rate and can detect minute gravity change due to the mass re-distribution at one ngal (periodic signal). Because gravity change from a SG is a combination of many sources and the contribution from Kuroshio change is potentially very weak (compared to background noises), it’s critical to develop optimal models of gravity corrections to remove signals not due to Kuroshio change. Gravity changes from GRACE have been used for climatic change studies in connection to oceanic mass re-distribution. The current spatial resolution of GRACE gravity change is about 250-300km, and is too coarse to detect the gravity change due to Kuroshio change. Using the KBR measurements and the GRACE obit information, this project will develop a regional solution that will improve the spatial resolution of GRACE gravity change. Satellite altimeter data from the missions Geosat, ERS-1, ERS-2, ENVISAT, TOPEX/Poseidon, Jason-1and Jason-2 (1986 to present), will be used to determine the long-term (more than 2 decades) changes in sea level, volume transport, width and axis over the Kuroshio Current area. A geoid model over the Kuroshio Current, with the reference field based on the GOCE global gravity model and the latest terrestrial gravity data, will be developed and the model will aid the determination of dynamic heights from altimeter data. This project will also develop a method to detect the variation of the bifurcation point of the North Equatorial Current (NEC) based on along-track dynamic height. An analysis of Kuroshio change and the NEC bifurcation point in connection to climate change will be made.