Journal Article Precise gravity-field modeling in the area of the Japanese Antarctic station Syowa and evaluation of recent EGMs

10 ( 1 )  , pp.101 - 109 , 2016-03
By combining a Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) Earth Gravity Model (EGM) and in situ gravity data obtained from the Japanese Antarctic Research Expedition (JARE) surveys, we estimated the regional gravity field in the area of Syowa Station, a Japanese research station located in Lützow-Holm Bay, East Antarctica. In situ data sets that were used consisted of land gravity data collected since 1967, shipborne data collected since 1985 and airborne gravity data collected in 2006. The GOCE direct (DIR) solution release 5 (R5) model was used as the long-wavelength reference of the gravity field. Using these data sets, we calculated gravity anomalies and geoid heights at 1-by-1′ grid by means of least-squares collocation.The resulting geoid height at Syowa Station was compared with a local height based on GPS, spirit leveling and tide gauge data. The result suggests that the sea surface height at Syowa Station is −1.57 m, which is consistent with a dynamic ocean topography model. During this investigation, we also evaluated GOCE EGMs and other recent EGMs by comparing them with the airborne gravity data. The results indicate that the GOCE DIR R5 produced the smallest RMS (Root Mean Square) differences and that the newer models performed nearly as well. These comparisons demonstrate the importance of using reliable in situ data when evaluating satellite-only EGMs.
日本の南極観測隊による1967年以降の地上重力、1985年以降のしらせ船上重力、および、2006年の航空重力データを用い、Gravity Field and Steady-State Ocean Circulation Explore (GOCE)のdirect solution (DIR) release 5 (R5) Earth Gravity Model (EGM)を長波長重力場の基準とし、最小2乗コロケーション法で、昭和基地周辺地域の1分格子上での重力異常とジオイド高を求めた。得られた昭和基地でのジオイド高と、GPS・水準測量・験潮データから求めたジオイド高とを比較することで、昭和基地での海面高を−1.57 mと推定した。この値は、海洋観測に基づく力学的海面高モデルの値と調和的である。また、航空重力データを用い、GOCEや他の最新のEGMの精度評価を行った。その結果、GOCE DIR R5が最も良い結果を示したが、他のEGMも同程度の精度であることが判った。

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