Extending the Record of Time-Variable Gravity by Combining Grace and Conventional Tracking Data

Talpe, Matthieu J.

Graduate Thesis Or Dissertation

Extending the Record of Time-Variable Gravity by Combining Grace and Conventional Tracking Data Public Deposited

Analytics

Citations

Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/xk81jk612

Abstract

The Gravity Recovery and Climate Experiment (GRACE) mission has provided invaluable insight on the behavior of mass redistribution on the surface of the Earth since its launch in March 2002. GRACE measures the range between its two satellites to obtain a new, high-resolution, global gravity field of the Earth every month. This dissertation presents the first record of high-resolution time-variable gravity that extends to the 1990s. This gravity reconstruction is obtained by combining GRACE with gravity solutions generated from conventional tracking of satellites that start in November 1992. These tracking observations originate from two ground-based systems, Satellite Laser Ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellites (DORIS). The statistical framework for the reconstructions of the two fields can be described in three major steps. First, high-resolution spatial patterns are obtained from a Principal Component Analysis (PCA) decomposition of GRACE gravity coefficients. In the second step, the top four patterns are used as the model relating the SLR/DORIS coefficients to their temporal modulation, which are solved for in a Least Squares Adjustment. Lastly, the full patterns and their temporal modulation are linearly combined to form gravity fields that span the SLR/DORIS time frame and therefore add a decade of perspective before GRACE. An error budget is also designed to quantify the influence of assumptions made in the reconstruction. The primary scientific goal was to add perspective on the behavior of polar ice sheet melt in the 1990s. The second goal was to extend the record of terrestrial water storage. One last application examined the possibility of using this technique as a way to bridge the upcoming multi-month gap between GRACE and its successor mission, GRACE Follow-On.

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