Simulation of oceanic bottom pressure for gravity space missions
Simulation of oceanic bottom pressure for gravity space missions
复制标题
重力空间任务的海底压力模拟
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
T. Gruber
中科院分区：
文献类型：
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作者：
J. Wünsch;Maik Thomas;T. Gruber
总结
洋底压力受海洋和大气中质量再分布的影响，它影响CHAMP、GRACE和GOCE新卫星任务从季节到短周期时间尺度的重力场测定。因此，需要考虑海洋中的质量再分布，以获得平均重力场。
采用汉堡海洋环流和潮汐模式（OMCT），利用ECHAM3实时模拟的大气动量、热量和淡水通量，计算了随时间变化的海底压力场。由此产生的底部压力场展开的重力场球谐系数作为时间的函数。时间分辨率为5天提取的年度和半年的振幅和6小时的研究高频变化。
为了评估海洋质量变化对重力场测量的影响，计算了模拟海底压力的度方差谱，并与空间任务的期望误差谱进行了比较。此外，大地水准面高度ΔN的变化从模拟斯托克斯系数示出。数值结果表明，海洋引起的长波重力变化成为可检测的CHAMP和GRACE重力任务。
SUMMARY
Oceanic bottom pressure is affected by mass redistribution in the ocean and atmosphere, and it influences gravity field determinations by the new satellite missions CHAMP, GRACE and GOCE from seasonal up to short-period timescales. Thus, mass redistribution in the ocean needs to be accounted for to obtain the mean gravity field.
With the Hamburg ocean model for circulation and tides (OMCT), time-dependent oceanic bottom pressure fields are calculated using atmospheric fluxes of momentum, heat and freshwater from ECHAM3 real-time simulations. The resulting bottom pressure fields are expanded in gravity field spherical harmonic coefficients as a function of time. The temporal resolution is 5 days for extracting annual and semi-annual amplitudes and 6 hr for studying high-frequency variations.
In order to estimate the influence of oceanic mass variations on gravity field determination, degree variance spectra of simulated bottom pressure are calculated and compared with the expected error spectra of space missions. Furthermore, variations in geoid height ΔN from the modelled Stokes coefficients are illustrated. The numerical results suggest that ocean-induced long-wavelength gravity variations become detectable with the CHAMP and GRACE gravity missions.