Observed Temporal Variations in the Earth’s Gravity Field from 16-year Starlette Orbit Analysis
Satellite laser ranging data to Starlette, collected during the period from 1975 to 1990, have been analyzed to determine yearly values of the second degree annual (S a ) and semiannual (S sa ) tides, simultaneously with average values of other low degree and order tide parameters. The yearly fluctuations in the values for S a and S sa are associated with changes in the Earth’s second degree zonal harmonic caused by meteorological excitation. The Starlette-determined mean values for the amplitude of the annual and semiannual variations in J 2 are 32.3 × lO−11 and 19.5 × lO−11, respectively; while the rms about the mean values are 4.1 × lO−11 and 6.3 × lO−11, respectively. The annual δJ 2 is in good agreement with the value obtained from the combined effects of air mass redistribution without the oceanic inverted-barometer effects (non-IB) and hydrological change. Approximately 90% of the observed annual variation from Starlette is attributed to the meteorological mass redistribution occurring on the Earth’s surface.
KeywordsOcean Tide Orbit Node Satellite Solution Tide Gauge Data Mass Redistribution
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