GRACE Time-Variable Gravity Field Recovery Using an Improved Energy Balance Formalism
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Date
2015-08
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Ohio State University. Division of Geodetic Science
Abstract
Earth’s gravity is continuously varying with respect to time due primarily to mass
transports within the Earth system and external gravitational forcing. A new formalism
based on energy conservation principle for time-variable gravity field recovery using
satellite gravimetry has been developed and yields more accurate estimation of in-situ
geopotential difference observables using K-Band Ranging (KBR) measurements from
the Gravity Recovery and Climate Experiment (GRACE) twin-satellite mission. The new
approach can preserve more time-variable gravity information sensed by KBR range-rate
measurements and reduce orbit error as compared to previous energy balance studies.
Results based on analysis of more than 10 years of GRACE data indicate that the
estimated geopotential differences agree well with the predicted values from official
Level 2 solutions: with much higher correlation of 0.9, as compared to 0.5–0.8 reported
by previous energy balance studies. This study demonstrates that the new approach is
more flexible for both global and regional temporal gravity recovery, leading to the first
independent GRACE monthly solution series based on energy conservation principle,
which is comparable to the results from different approach. The developed formalism is
applicable to the general case of low-low satellite-to-satellite radiometric or laser
interferometric tracking measurements, such as GRACE Follow-on or other Next
Generation Gravity Field missions, for efficient retrieval and studies of Earth’s mass
transport evolutions.
The regional gravity analysis over Greenland reveals that a substantially higher temporal
resolution is achievable at 10 or 11-day interval from GRACE data, as compared to the
official monthly solutions, but without the compromise of spatial resolution, nor the need
to use regularization or post-processing. Studies of the terrestrial and ground water
storage change over North China Plain show high correlation in sub-monthly scale,
among the 11-day time-variable gravity solutions from this study, in-situ data, and
hydrologic and atmospheric models. The 11-day solutions with 1-day step successfully
capture the surface mass change caused by the rapid snow and ice accumulation and
melting during the extreme weather event of 2008 Southeast China snow and ice storm.
These results demonstrated that sub-monthly solutions from GRACE can provide an
additional constraint to understand the rapid mass transport and the dynamic processes
for both extreme weather events and short-time surface and ground water monitoring,
which may potentially improve our understanding of various mass transports within the
Earth system, and applicable to societal services such as disaster response or mitigation,
and water resources management.
Description
This Report was prepared for and submitted to the Graduate School of the Ohio State University as a dissertation in partial fulfillment of the requirements for the PhD degree.
This research is conducted under the supervision of Professor C.K. Shum, Division of Geodetic Science, School of Earth Sciences, The Ohio State University. This research is partially supported by grants from NSF via the Belmont Forum/IGFA Grant (ICER- 1342644), and NASA’s geodesy and cryosphere grants (NNX12AJ95G, NNX12AK28G, NNX11AR47G). GRACE data products are from NASA’s PODAAC via Jet Propulsion Laboratory/California Institute of Technology (JPL), University of Texas Center for Space Research (CSR), and GeoForschungsZentrum Potsdam (GFZ). Some figures in this paper were generated using the Generic Mapping Tools (GMT) [Wessel and Smith, 1991]. The computational aspect of this work was supported in part by an allocation of computing resources from the Ohio Supercomputer Center (http://www.osc.edu).
This research is conducted under the supervision of Professor C.K. Shum, Division of Geodetic Science, School of Earth Sciences, The Ohio State University. This research is partially supported by grants from NSF via the Belmont Forum/IGFA Grant (ICER- 1342644), and NASA’s geodesy and cryosphere grants (NNX12AJ95G, NNX12AK28G, NNX11AR47G). GRACE data products are from NASA’s PODAAC via Jet Propulsion Laboratory/California Institute of Technology (JPL), University of Texas Center for Space Research (CSR), and GeoForschungsZentrum Potsdam (GFZ). Some figures in this paper were generated using the Generic Mapping Tools (GMT) [Wessel and Smith, 1991]. The computational aspect of this work was supported in part by an allocation of computing resources from the Ohio Supercomputer Center (http://www.osc.edu).