American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Read Full Article (file size: 394386 bytes)    Cited by

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, B09402, doi:10.1029/2004JB003028, 2004

Variations in the Earth's oblateness during the past 28 years

Minkang Cheng

Center for Space Research, University of Texas at Austin, Austin, Texas, USA


Byron D. Tapley

Center for Space Research, University of Texas at Austin, Austin, Texas, USA


Abstract

Analysis of satellite laser ranging (SLR) data indicates that the Earth's dynamic oblateness (J 2) has undergone significant variations during the past 28 years. The dominant signatures in the observed variations in J 2 are (1) a secular decrease with a rate of approximately −2.75 × 10−11 yr−1, (2) seasonal annual variations with a mean amplitude of 2.9 × 10−10, (3) significant interannual variations with timescales of 4–6 years, and (4) a variation with period of ∼21 years and an amplitude of ∼1.4 × 10−10 with minimum in December 1988. Two large interannual variations are related to the strong El Niño-Southern Oscillation events during the periods of 1986–1991 and 1996–2002, and it appears that another interannual cycle may have started in late 2002. The superposition of the decadal variation on the interannual signal makes the J 2 fluctuation appear to be anomalously large during the 1996–2002 period. Contemporary models of the mass redistributions in the atmosphere, ocean, and surface water can explain a major part of the 4- to 6-year fluctuations. However, the cause of the decadal variation remains unknown.

Received 18 February 2004; accepted 6 July 2004; published 16 September 2004.

Keywords: SLR; J2 variation; ENSO.

Index Terms: 1214 Geodesy and Gravity: Geopotential theory and determination; 1241 Geodesy and Gravity: Satellite orbits; 1223 Geodesy and Gravity: Ocean/Earth/atmosphere interactions (3339); 1249 Geodesy and Gravity: Tides—Earth.

Read Full Article (file size: 394386 bytes)    Cited by

Citation: Cheng, M., and B. D. Tapley (2004), Variations in the Earth's oblateness during the past 28 years, J. Geophys. Res., 109, B09402, doi:10.1029/2004JB003028.