Satellite gravity surveying is currently a worldwide hot topic in the area of Geodesy. For the first time, the gravity satellite GRACE (Gravity Recovery And Climate Experiment) provides gravity measurements for nearly 15 years. Those observations are unprecedented high-precision data for earth physical phenomenon such as global hydrological signals, climate extreme anomalies, seismology. GRACE opened new era of high-precision global gravity measurements and climate- change experiments. It is also a powerful tool for the monitoring of the global environmental change (melting of continental glacial, change of sea level and ocean circulation, change of land water storage, intense earthquake).
The satellite gravity research team of our faculty led by Prof. Dongming Fan devoted to the computation and application of high-precision static and time-varying earth gravity model over a long-period of time. The researchers carried out by Prof. Dongming Fan research team have attracted attentions at home and aboard. Recently, the team member PhD candidate Yanchao Gu wrote a paper under the directions of Prof. Dong Fan and Dr. Wei You. The paper was later published by the journal of Geophysical Research Letters which is an international top journal in the area of Geosciences. It’s the first time for SWJTU to be the first sign unit of the papers from this journal. The paper received high comments from reviewers (Reviewer's comments: This paper is the first to do systematic comparisons across both the various GPS and GRACE solutions. This allows them to quantify which of the IGS solutions are discrepant with respect to the others, and to quantify one component of the error in the GPS time series)。This highly approved that the researches of thedisciplineof mapping and surveying are keeping up with the international academic front-line, and are able to solve the problems in the large-scale monitoring via high-precisionsatellite surveyingtechniques.
Geophysical Research Letters (GRL) is a biweeklypeer-reviewedscientific journalofgeosciencepublished by theAmerican Geophysical Union. GRL belongs to the first-tier journals in the SCI indexed journal ranking published by Chinese Academy of Sciences. According to theJournal Citation Reports, the journal has a 2016-2017impact factorof 4.253, and a 5 years impact factor 4.579. GRL is one of the highly sited journals on Geosciences.
Tidal and non-tidal mass variations on the Earth’s surface induce crustal vertical displacements (CVD) due to the elasticity of the Earth’s crust. The tidal loading models are accurately modeled so that they can be removed during data processing of GPS and other space geodesy systems. However, the non-tidal models are still deemed to contain large uncertainties. The sources of the differences between GPS and GRACE data are a challenging problem, which needs to be fully resolved before considering the use of combined GRACE and GPS data in Earth system science, in applications such as correcting the non-tidal effect in GPS data processing.
The paper published on GRL shows that The result of the cross comparison indicates that the non-tidal effects represented by the GRACE solutions can explain as much as 50% of the GPS common signals, and more than 80% of the GPS annual signals. The results of the paper strongly suggest that most of the residuals between GPS and GRACE CVD data can be attributed to GPS post-processing errors, and the effects of the coarse resolution of the GRACE products and other influencing factors are insignificant with respect to the large inaccuracy of GPS estimates. The GRACE CVD data are robust and hence have great potential to correct the non-tidal loading in GPS time series.
Detailed information of the paper: Gu, Y., D. Fan, and W. You (2017), Comparison of observed and modeled seasonal crustal vertical displacements derived from multi-institution GPS and GRACE solutions, Geophys. Res. Lett., 44, doi:10.1002/2017GL074264.
Online：http://onlinelibrary.wiley.com/doi/10.1002/2017GL074264/full
