Long-term variations in the second sectorial Stokes harmonics on the basis of TOPEX/POSEIDON altimetry between 1993 and 2000

článek v časopise - ostatní, Jost

angličtina

The long-term variations in the second degree sectorial Stokes parameters of the geopotential have been determined from TOPEX-POSEIDON (T/P) satellite altimeter data, covering the period of January 1, 1993 to January 3, 2001 (T/P cycles 11-305). It is the first attempt to determine the variations in the second sectorial harmonics in the Earths inertia tensor due to the ocean dynamics. The variations amount to about 1 x 10-10 (J 2 (2) ? 1.6 x 10-6 and S 2 (2) ? -0.9 x 10-6). The variations are about 5% of the tidal effect. This corresponds to variations in the directions of the equatorial axes of the Earths inertia ellipsoid of up to 10 arc-seconds. Consequently, the annual and semi-annual variations of the Earths equatorial flattening is about 10-9; i.e. it corresponds to a change of 8 units of its denominator of 91 030. (The equatorial flattening ? 1/91 030). Since the coverage of the Earths ocean surface is not worldwide, and the inclination of T/P is i = 66, it is only 58.2% (min. depth of the ocean 2 000 m) of the Earths surface which is processed, the torque, resulting from the seasonal transfer of masses within a sea surface layer, is not zero. It amounts up to 1016 kg m2s-2, which is comparable to the total indirect tidal torque due to the Moon and the Sun, ~ 3.9 x 1016 kg m2s-2. However, the above estimate strongly depends on the adopted thickness of the sea surface layer, ?R = 50 m. For a larger thickness of ?R = 100 m, the seasonal torque amounts to about ~ 2.3 x 1016 kg m2s-2.

Earths inertia tensor - equatorial axes directions - equatorial flattening variations - T/P altimetry

BURŠA, M., KENYON, S., KOUBA, J., ŠÍMA, Z., VATRT, V., VÍTEK, V. and VOJTÍŠKOVÁ, M.

2006

26. 10. 2006

0039-3169

STUDIA GEOPHYSICA ET GEODAETICA

50

4

Česká republika

509

524

16