Journal
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
Volume 127, Issue 2, Pages -Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2021JB022983
Keywords
GRACE Follow-On; LRI; LGD; sub-monthly mass change; time-variable gravity
Categories
Funding
- University of Newcastle
- Australian Research Council [DP160104095, DP170100224]
- NASA [GRACERFO19-0010]
- National Aeronautics and Space Administration [80NM0018D0004]
- German Research Foundation [DO 1311/4-1]
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This article examines the sensitivity of GRACE-FO LRI measurements to sub-monthly time-variable gravity signals and presents an alternative analysis method for studying short-term mass changes. By combining the LRI observations with other data and models, high-frequency oceanic mass variability and sub-monthly variations in surface water can be detected.
We examined the sensitivity of GRACE Follow-On (GRACE-FO) laser ranging interferometer (LRI) measurements to sub-monthly time-variable gravity (TVG) signals caused by transient, high-frequency mass changes in the Earth system. GRACE-FO LRI provides complementary inter-satellite ranging measurements with higher precision over a wider range of frequencies than the baseline K-band microwave ranging system. The common approach for studying mass variation relies on the inverted TVG or mascon solutions over a period of, for example, one month or 10 days which are adversely affected by temporal aliasing and/or smoothing. In this article, we present the alternative along-orbit analysis methodology in terms of line-of-sight gravity difference (LGD) to fully exploit the higher precision LRI measurements for examination of sub-monthly mass changes. The discrepancy between instantaneous LGD LRI observations and monthly-mean LGD (from Level-2 data) at satellite altitude indicates the sub-monthly gravitational variability not captured by monthly-mean solutions. In conjunction with the satellite ocean altimetry observations, high-frequency non-tidal atmosphere and ocean models, and hydrology models, we show that the LGD LRI observations detect the high-frequency oceanic mass variability in the Argentine Basin and the Gulf of Carpentaria, and sub-monthly variations in surface (river) water in the Amazon Basin. We demonstrate the benefits gained from repeat ground track analysis of GRACE-FO LRI data in the case of the Amazon surface water flow. The along-orbit analysis methodology based on LGD LRI time series presented here is especially suitable for quantifying temporal and spatial evolution of extreme, rapidly changing mass variations.
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