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Updated: Jul 13, 2026

Measurements of Soil Carbon by Neutron-Gamma Analysis in Static and Scanning Modes
Published on: August 24, 2017
GRACE measurements of mass variability in the Earth system
Byron D Tapley1, Srinivas Bettadpur, John C Ries
1Center for Space Research, University of Texas, Austin, TX 78712, USA.
Abstract:
Monthly gravity field estimates made by the twin Gravity Recovery and Climate Experiment (GRACE) satellites have a geoid height accuracy of 2 to 3 millimeters at a spatial resolution as small as 400 kilometers. The annual cycle in the geoid variations, up to 10 millimeters in some regions, peaked predominantly in the spring and fall seasons. Geoid variations observed over South America that can be largely attributed to surface water and groundwater changes show a clear separation between the large Amazon watershed and the smaller watersheds to the north. Such observations will help hydrologists to connect processes at traditional length scales (tens of kilometers or less) to those at regional and global scales.
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