AbstractDiurnal S$$_1$$1 tidal oscillations in the coupled atmosphere–ocean system induce small perturbations of Earth’s prograde annual nutation, but matching geophysical model estimates of this Sun-synchronous rotation signal with the observed effect in geodetic Very Long Baseline Interferometry (VLBI) data has thus far been elusive. The present study assesses the problem from a geophysical model perspective, using four modern-day atmospheric assimilation systems and a consistently forced barotropic ocean model that dissipates its energy excess in the global abyssal ocean through a parameterized tidal conversion scheme. The use of contemporary meteorological data does, however, not guarantee accurate nutation estimates per se; two of the probed datasets produce atmosphere–ocean-driven S$$_1$$1 terms that deviate by more than 30 $$\upmu $$μas (microarcseconds) from the VLBI-observed harmonic of $$-16.2+i113.4$$-16.2+i113.4 $$\upmu $$μas. Partial deficiencies of these models in the diurnal band are also borne out by a validation of the air pressure tide against barometric in situ estimates as well as comparisons of simulated sea surface elevations with a global network of S$$_1$$1 tide gauge determinations. Credence is lent to the global S$$_1$$1 tide derived from the Modern-Era Retrospective Analysis for Research and Applications (MERRA) and the operational model of the European Centre for Medium-Range Weather Forecasts (ECMWF). When averaged over a temporal range of 2004 to 2013, their nutation contributions are estimated to be $$-8.0+i106.0$$-8.0+i106.0 $$\upmu $$μas (MERRA) and $$-9.4+i121.8$$-9.4+i121.8 $$\upmu $$μas (ECMWF operational), thus being virtually equivalent with the VLBI estimate. This remarkably close agreement will likely aid forthcoming nutation theories in their unambiguous a priori account of Earth’s prograde annual celestial motion.

中文翻译：

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全球 S $$_1$$ 1 地球章动潮汐


摘要大气-海洋耦合系统中的每日 S$$_1$$1 潮汐振荡会引起地球顺行年章动的小扰动，但将太阳同步旋转信号的地球物理模型估计与大地测量甚长基线干涉测量 (VLBI) 中观测到的效果相匹配迄今为止，数据一直难以捉摸。本研究从地球物理模型的角度评估了这个问题，使用了四个现代大气同化系统和一个持续强制正压海洋模型，该模型通过参数化潮汐转换方案消散全球深海海洋中的多余能量。然而，使用当代气象数据本身并不能保证章动估计的准确性。两个探测数据集产生大气-海洋驱动的 S$$_1$$1 项，与 VLBI 观测到的谐波 $$-16.2+i113.4$ 偏差超过 30 $$\upmu $$μas（微弧秒） $-16.2+i113.4 $$\upmu $$μas。这些模型在昼夜带中的部分缺陷也通过气压潮与气压现场估计的验证以及模拟海面高度与 S$$_1$$1 潮汐计测定的全球网络的比较得到证实。可信度借给全球 S$$_1$$1 潮汐，该潮汐源自现代研究和应用回顾分析 (MERRA) 以及欧洲中期天气预报中心 (ECMWF) 的运行模型。当在 2004 年至 2013 年的时间范围内进行平均时，它们的章动贡献估计为 $$-8.0+i106.0$$-8.0+i106.0 $$\upmu $$μas (MERRA) 和 $$-9.4+ i121.8$$-9.4+i121.8 $$\upmu $$μas（ECMWF 运行），因此实际上与 VLBI 估计相当。 这种非常接近的一致性可能会有助于即将出现的章动理论，以明确地先验地解释地球每年顺行的天体运动。