Atmospheric excitation of the Earth's free core nutation
Atmospheric excitation of the Earth's free core nutation
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DOI：
10.1051/0004-6361:20065813
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发表时间：
2006-10
影响因子：
6.5
通讯作者：
S. Lambert
中科院分区：
文献类型：
--
作者：
S. Lambert
目标。本文研究了大气压力变化对地球自由核章动(RFCN)的时变激发作用。方法：研究方法。导出了外部流体层气压日变化引起的RFCN的幅值。利用国家环境展望中心/国家大气研究中心(NCEP/NCAR)再分析项目数据集研究了大气激发的个例。结果。白天的大气激发大约是解释观测到的RFCN幅度所需的一半。此外，大气噪声的时间变异性不能解释在1984-2006年期间观测到的RFCN幅度的变异性。研究了可能的误差来源，如压力系数、RFCN品质因数或随时间变化的RFCN表观周期，但不能解释这种差异。结论。在日间频率的大气模拟方面需要改进。在实现这一点之前，观测到的RFCN与其大气激发之间的物理联系，特别是关于其时间变异性的物理联系，将仍然不清楚。
Aims. This study investigates the time-varying excitation of the Earth's retrograde free core nutation (RFCN) by atmospheric pressure variations. Methods. The amplitude of the RFCN resulting from diurnal pressure variations in the external fluid layers is derived. The case of atmospheric excitation is investigated using the National Center for Environmental Prospect/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis project data set. Results. The diurnal atmospheric excitation is about half that required to explain the observed RFCN amplitude. Moreover, the time variability of the atmospheric noise does not account for the observed variability of the RFCN amplitude over the time period 1984-2006. Possible sources of error like the pressure coefficient, the RFCN quality factor, or the time varying RFCN apparent period are investigated but cannot account for the discrepancy. Conclusions. Improvements are needed in atmospheric modeling at diurnal frequencies. Until this is achieved, the physical link between the observed RFCN and its atmospheric excitation, especially concerning its time variability, will remain unclear.