全球定位系統浮標運用於衛星測高儀絕對率定

The Use of Global Postitioning System Buoys in Absolute Calibration of Radar Altimetry

近年來衛星測高儀（satellite altimetry）已經發展成為一成熟的海洋資料收集工具，但是其資料還未能完全用於全球海水變遷研究上，因為衛星測高儀觀測量與實際海水高度存在有一固定偏差（bias），其大小約在數公釐至數公分不等。然而目前公認的全球海水面上升趨勢約為每年1至2公釐左右，因此必須借助其他獨立的資料收集工具，例如：全球定位系統（Global Positioning System, GPS）浮標（buoys）、潮位站（tide gauges）等，率定衛星測高儀所測之海面橢球（sea surface height, ssh），以滿足海水監測與全球海面變遷等相關研究之需求。本研究提出一簡易方法，針對JASON-1測高衛星，於美國五大湖的伊利湖，利用全球定位系統浮標及潮位站建一持續率定站。不僅可避免建造昂貴的水面固定率定平台，且具有持續率定功能，所得率定結果與美國Harvest平台與法國科西嘉島（Corsica）等固定式率定站之率定結果接近。率定結果有助於提昇衛星測高儀之觀測精度，進而能供全球海水變遷分析與精確海面監測等研究。 Satellite altimetry has evolved as an effective tool for observing global oceanic phenomena with unprecedented precision in the sea surface height. Since studies of global sea level rise using satellite altimetry examine the signal whose magnitude is about 1–2 mm/year, the altimeter range bias and the drift should be calibrated and accounted for with the calibration sites around the world. In this study, a continuous calibration site in Lake Erie of the U.S. was established using a Global Positioning System (GPS) buoy and a tide gauge. The proposed approach is cost-effective since it does not require building a stationary offshore platform. The calibration result is comparable to other dedicated calibration sites and can ultimately benefit the studies of global sea level monitoring and sea level trend determination.

Satellite altimetry has evolved as an effective tool for observing global oceanic phenomena with unprecedented precision in the sea surface height. Since studies of global sea level rise using satellite altimetry examine the signal whose magnitude is about 1–2 mm/year, the altimeter range bias and the drift should be calibrated and accounted for with the calibration sites around the world. In this study, a continuous calibration site in Lake Erie of the U.S. was established using a Global Positioning System (GPS) buoy and a tide gauge. The proposed approach is cost-effective since it does not require building a stationary offshore platform. The calibration result is comparable to other dedicated calibration sites and can ultimately benefit the studies of global sea level monitoring and sea level trend determination.