Nontidal oceanic contribution to length-of-day changes estimated from two ocean models during 1992-2001
Nontidal oceanic contribution to length-of-day changes estimated from two ocean models during 1992-2001
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DOI：
10.1029/2004jb003538
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发表时间：
2006-02
影响因子：
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通讯作者：
Haoming Yan;M. Zhong;Yao-zhong Zhu;Lintao Liu;Xianhe Cao
中科院分区：
文献类型：
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作者：
Haoming Yan;M. Zhong;Yao-zhong Zhu;Lintao Liu;Xianhe Cao
[1]利用斯克里普斯海洋研究所和马里兰州大学开发的两个不同的海洋环流模式产品，在季节时间尺度上评估了1992-2001年期间洋底压力和海流对日长变化的贡献。海洋角动量（OAM）的两个底压项的年振幅相差约3倍，而它们的年相位是相似的。将重力引起的非大气LOD变化与两个OAM底压项在年频率上进行比较，发现在相位上有明显的差异。这一结果表明，激发LOD变化的其他来源，如水文，也很重要。两个OAM电流项的年度振幅和相位比较以及与观测到的LOD减去重力派生的LOD变化和轴向大气角动量风项，但只有当风的影响之间的10和0.3 hPa的水平不包括在后者。这两个OAM系列有相似的季节振幅和相位，但他们有很大的差异时，在不同的纬度带检查。两次OAM引起的LOD变化的年振幅与非大气LOD变化的年振幅相当，但半年振幅要小得多。我们的研究表明，海洋对LOD的影响应继续研究。此外，在半年频率上，纬向风（10- 0.3hPa）对LOD的影响比地面气压的影响更显著，而在年频率上，两者的作用几乎相同。
[1] Contributions of ocean bottom pressure and currents to changes in the length of day (LOD) during 1992–2001 are evaluated at seasonal timescales by using two different ocean general circulation model products developed at the Scripps Institution of Oceanography and the University of Maryland. The annual amplitudes for the two bottom pressure terms of oceanic angular momentum (OAM) differ by approximately a factor of 3, while their annual phases are similar. Comparing the gravity-derived nonatmosphere LOD changes with the two OAM bottom pressure terms at annual frequency, we find obvious discrepancies in phase. This result indicates that excitation of LOD changes by other sources, such as hydrology, is also important. The annual amplitudes and phases of the two OAM current terms compare well with those of the observed LOD minus gravity-derived LOD changes and axial atmosphere angular momentum wind term but only if wind effects between 10 and 0.3 hPa levels are not included in the latter. The two OAM series have similar seasonal amplitudes and phases, but they differ substantially when examined in different latitudinal bands. The annual amplitudes of two OAM-induced LOD changes are comparable with that of the nonatmosphere LOD changes, but the semiannual amplitudes are far smaller. Our study indicates that the oceanic effects on LOD should continue to be examined. In addition, the effects of zonal winds (10–0.3 hPa) on LOD are more significant than that of atmospheric surface pressures at semiannual frequency, while they play almost the same roles for annual term.