Improved geoid model determination for Japan from GRACE and a regional gravity field model

Yuki Kuroishi

doi:10.1186/bf03353191

Abstract

Abstract A highly improved gravimetric geoid model for Japan, JGEOID2008, is developed on a 1×1.5 arc-minute grid by combining a GRACE (the Gravity Recovery And Climate Experiment)-based global geopotential model, GGM02C, surface (land and ship-borne) gravity measurements, and an altimetry-derived marine gravity model, KMS2002. In the combination, a semidiscrete two-dimensional wavelet analysis/reconstruction method is employed, selecting the spatial wavelength signals of the highest quality out of the respective data sets. Intercomparison with GPS/leveling geoid undulations shows substantial improvement of JGEOID2008 over the previous model, JGEOID2004, and reveals that the systematic errors at long wavelengths contained in JGEOID2004 have been effectively removed. Deviations of JGEOID2008 from the mean sea surface height at tidal stations on isolated islands were comparable to the differences in the sea surface dynamic heights (SSDH) in the Japan Sea, the Nansei Islands and the Izu Island chain from that in Tokyo Bay. The deviations show good agreement with SSDH features estimated from oceanographic observation, indicating that JGEOID2008 has an accuracy within 10 cm. The geoid model is strongly expected to serve as a reference in ocean dynamics studies.

Highlights

The success of the dedicated satellite gravity missions, such as the Gravity Recovery And Climate Experiment (GRACE), to directly observe the Earth’s gravity field and its temporal changes on a global scale has been yielding breakthroughs in multidisciplinary studies of geodynamics
JGEOID2008 is compared with the same GPS/leveling geoid undulations at 816 benchmarks that cover the four major islands of Japan, i.e., Honshu, Hokkaido, Shikoku, and Kyushu
Ship-borne gravity data are corrected with KMS2002, which is low-pass filtered by a semidiscrete 2D wavelet analysis/reconstruction method at a cutoff wavelength of about 1.25◦ after the removal of erroneous coastal areas

Summary

Introduction

The success of the dedicated satellite gravity missions, such as the Gravity Recovery And Climate Experiment (GRACE), to directly observe the Earth’s gravity field and its temporal changes on a global scale has been yielding breakthroughs in multidisciplinary studies of geodynamics. Deviations of JGEOID2008 from the mean sea surface height at tidal stations on isolated islands were comparable to the differences in the sea surface dynamic heights (SSDH) in the Japan Sea, the Nansei Islands and the Izu Island chain from that in Tokyo Bay. The deviations show good agreement with SSDH features estimated from oceanographic observation, indicating that JGEOID2008 has an accuracy within 10 cm.

Results

Conclusion