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| Titel |
Comparison of gravity changes from the Hsinchu superconducting gravimeter (T048) and GRACE: effects of low-degree gravity and local hydrology |
| VerfasserIn |
Tzu-Yi Lien, Cheinway Hwang, Ching-Chung Cheng |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250038653
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| Zusammenfassung |
| A superconducting gravimeter delivers point gravity measurements. Gravity changes from
GRACE have limited spatial resolutions due to satellite altitude, measurement/correction
noises and filtering. This paper compares gravity changes from the Hsinchu (HS)
superconducting gravimeter (SG, T048) and GRACE. The HS SG station is near the Taiwan
Strait which is about 120-160 km in width. Taiwan is an island at a largest width of 120 km,
with the Pacific Ocean to its east. Thus, residual SG gravity changes at HS, obtained by
removing the gravity effects due to solid earth tide, ocean tidal loading, atmospheric pressure,
contain the local hydrological effect (first-order effect) and the effect due to phenomena
at spatial resolutions beyond the local hydrological scale (second-order effect, at
about a spherical harmonic expansion to degree 100). Various combinations of
low-degree harmonics from GRACE and SLR are used to generate various second-order
effects, which are then removed from SG gravity to produce first-order effects.
Soil moisture and groundwater levels are used to model the firs-order effect for
comparison with the SG-measured first-order effect. It is found (1) groundwater
and soil moisture-derived first-order effects have a phase lag of about 60 days. (2)
SLR-derived J2 coefficient delivers a better match of the second-order effect with
SG measurements than GRACE-derived J2, (3) The nominal maximum harmonic
expansion degree of 100 does not produce the best second-order effect. Several
experimental computations of the first-order effect will be presented in the paper. |
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