| Project/Area Number |
13440135
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体地球物理学
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| Research Institution | National Astronomical Observatory |
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Principal Investigator |
SATO Tadahito National Astronomical Observatory, Assistant Prof., 電波研究部, 助教授 (10000176)
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| Co-Investigator(Kenkyū-buntansha) |
TAMURA Yoshiaki National Astronomical Observatory, Assistant Prof., 電波研究部, 主任研究員 (90150002)
HIGASHI Toshihiro Kyoto University, Graduate School of Science, Assistant Prof., 大学院・理学研究科, 助手 (90135517)
FUJIMOTO Hiromi Tohoku University, Graduate School of Science, Prof., 大学院・理学研究科, 教授 (50107455)
MATSUMOTO Koji National Astronomical Observatory, Assistant Prof., 電波研究部, 上級研究員 (30332167)
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| Project Period (FY) |
2001 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥14,500,000 (Direct Cost: ¥14,500,000)
Fiscal Year 2003: ¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 2002: ¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 2001: ¥10,000,000 (Direct Cost: ¥10,000,000)
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| Keywords | Ocean bottom pressure gauge / Satellite altimetry / Satellite gravimetry / Absolute gravimeter / Superconducting gravimeter / Sea surface height variability / Variation in gravity / Free core resonance / 衛星高度計観測 / 海水面変動による質量移動 / 衛星高度計 / 衛星重力 / 地球重力場の変動 / 年周重力変化 / 温度ステリック係数 |
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| Research Abstract |
Seafloor pressure monitoring is an indispensable approach to study the effect of seawater mass changes on the Earth's gravity, which also link to the air mass motions. For example, Cox and Chao (2002) claimed the mass exchange in the Pacific Ocean as a major source of the recent rapid and large change in the J2 term of the Earth's gravity may related to the huge ENSO event terminated in the end of 1997. Our group detected the actual pressure changes at that event from the ocean bottom pressure (OBP) observations (Fujimoto et al., Geophysical Research Letters, 2003).
Satellite gravimetry (CHAMP and GRACE) is expected to reveal the global relation between the ocean variability and the gravity change. Since 2001, we are carrying out OBP observations at the cross-over points of the TOPEX/Poseidon (TIP) altimeter tracks in the western Pacific Ocean (off Sanriku) in order to investigate the effect of OBP changes on the gravity. We have compared the observations at two sites of OBP-A (about 100 km from sea coast) and OBP-B (about 350 km) with the thee different kinds of data sets. These are (1) the four ocean tide models based on the T/P data, (2) the sea surface height (SSH) variations obtained from the T/P and (3) the pressure changes derived from the ECCO model (Stammer et al., 2002). Our comparison results suggest that it is still needed to carefully examine the effects of ocean mass transportations on the satellite gravimetry which aims at monthly geoid determination at an accuracy of 1 cm or better, and the OBP observation is a useful method for validation of the satellite gravimetry (submitted to GRL).
The supper-conducting gravimeter at Esashi well calibrated with the absolute gravimeters have been used to check the tide models and to revise the free core resonance parameters (Sato et al., Journal Geodynamics, 2004, accepted).
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