An Analysis of Tidal Variations In the Length of Day

McCarthy, Dennis D.; Luzum, Brian

doi:10.1111/j.1365-246x.1993.tb03922.x

Cited by 14 publications

(5 citation statements)

References 23 publications

(34 reference statements)

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“…Brosche et al (1991) report general agreement between the Brosche et al (1989) fortnightly ocean tidal predictions and recent VLBI UT1 data. McCarthy & Luzum (1991) find that the bulk of the power in long-period 1.o.d. observations (from a combined VLBI, SLR, and LLR data set) can be accounted for when the entire Brosche et al (1989) long-period model (as well as atmospheric angular momentum effects) are incorporated into the standard set of UT1 corrections.…”

Section: Comparisons With Observationsmentioning

confidence: 97%

Dynamic Ocean-Tide Effects On Earth's Rotation

Dickman

1993

Geophysical Journal International

123

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This article develops 'broad-band' Liouville equations which are capable of determining the effects on the rotation of the Earth of a periodic excitation even at frequencies as high as semi-diurnal; these equations are then used to predict the rotational effects of altimetric, numerical and 32-constituent spherical harmonic ocean-tide models. The rotational model includes a frequency-dependent decoupled core, the effects of which are especially marked near retrograde diurnal frequencies; and a fully dynamic oceanic response, whose effects appear to be minor despite significant frequency dependence. The model also includes solid-earth effects which are frequency dependent as the result of both anelasticity at long periods and the fluid-core resonance at nearly diurnal periods.The effects of both tidal inertia and relative angular momentum on Earth rotation (polar motion, length of day, 'nutation' and Universal Time) are presented for 32 long-and short-period ocean tides determined as solutions to the author's spherical harmonic tide theory. The lengthening of the Chandler wobble period by the pole tide is also re-computed using the author's full theory. Additionally, using the spherical harmonic theory, tidal currents and their effects on rotation are determined for available numerical and altimetric tide height models. For all models, we find that the effects of tidal currents are at least as important as those of tide height for diurnal and semi-diurnal constituents.

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Section: Comparisons With Observationsmentioning

confidence: 97%

Dynamic Ocean-Tide Effects On Earth's Rotation

Dickman

1993

Geophysical Journal International

123

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“…Several studies in the past have attempted to estimate k or k/C from observations of UT1 using a variety of observing techniques including classical optical, satellite laser ranging, and VLBI ob•servations [Pil'nik, 1970;Guinot, 1970;Guinot, 1974;Djurovik, 1976;Hefty, 1982;Capitainc and Guinot, 1985;Merriam, 1985;Luo et al, 1987;Newhall et al, 1988;Robertson et al, 1988;$chuh, 1988;Pejovi6 and Vondrdk, 1989;Hefty and Capitainc, 1990;Nam and Dickman, 1990;Brosche et al , 1991;McCarthy and Luzum, 1993]. This paper reports the results of our analysis of 9 years of VLBI UT1 values.…”

Section: Discussion Of the Problemmentioning

confidence: 99%

Tidal variations in UT1 observed with very long baseline interferometry

Robertson¹,

Ray²,

Carter³

1994

J. Geophys. Res.

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Nine years of very long baseline interferometry (VLBI) observations have been analyzed to determine the magnitudes of the tidal variations in UTl for periods between 5 and 35 days. Corrections for variations in atmospheric angular momentum (AAM) significantly reduce the scatter of the measured amplitudes across both time and frequency. The AAM corrections are found to reduce the scatter in the observed tidal amplitudes by as much as 60% for periods as short as 5.6 days; in contrast, earlier studies have shown a loss of coherence between AAM and length‐of‐day (LOD) for periods shorter than about 10 days. The tidal amplitude measurements place bounds on both the nonequilibrium ocean and mantle anelasticity effects. The in‐phase k/C determination is found to agree to better than 0.5% with the value of 0.944 from Yoder et al. (1981). The out‐of‐phase values are found to have a frequency dependence that can only be explained by nonequilibrium ocean effects. The observed slope is larger than the theoretical by about 3 times the expected error. This result may indicate that the ocean is farther out of equilibrium for the higher frequencies than present models permit. Significant improvements are needed in both ocean and atmosphere modeling to exploit the full capability of the VLBI observations.

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“…Analogous plots are done for the imaginary part κ im in Figure 2. As shown more than two decades ago (Chao et al, 1995;Defraigne & Smits, 1999;McCarthy & Luzum, 1993;Merriam, 1984), the error bars and the dispersion are strikingly squeezed by considering the atmospheric correction (case 2/4). The improvement resulting from the additional ocean correction can be noticed for the real part at many tidal periods, where oceans bring the estimated value toward the mean (13.78 days,MSf,27.44 days,27.68 days,MSm,Ssa) despite a large uncertainty for some waves.…”

Section: Table 2 Estimated Admittances For the Lod (Space Series) Cor...mentioning

confidence: 95%

“…In the 1990's, thanks to VLBI observations, the LOD was determined with a precision of about 0.02 ms. Removing the atmospheric correction from LOD, McCarthy and Luzum (1993) concluded that dynamical ocean tides, as modeled by Dickman (1993) or Wuensch and Busshoff (1992), are more relevant than equilibrium ones for calculating the LOD oscillations at zonal tide periods, and Chao et al (1995) determined the admittances of 11 zonal tides between 2 and 35 days with an uncertainty smaller than 0.05. In order to account for these progresses, Defraigne and Smits (1999) slightly improved the model of Yoder and Williams (1981), addressing a three layered Earth (an anelastic inner core, an inviscid fluid core and an anelastic mantle) and the dynamical effect of the ocean tides.…”

Section: 1029/2021jb022962mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Admittance of the Earth Rotational Response to Zonal Tide Potential

2022

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This study is devoted to the determination of the admittance parameters describing the Earth rotational response to the components of the zonal tide potential. First, in order to better grasp the physical content of those admittance coefficients, we revisit the theoretical description of the length of day (LOD) changes at sub‐decadal time scale, where forcing is dominated by zonal tides and hydro‐atmospheric mass transports. This theoretical reminder specifies the rheological coefficients permitting to apply the hydro‐atmospheric corrections to isolate the tidal part of the LOD. Then, the admittances are determined from the LOD series corrected from hydro‐atmospheric contributions at the frequencies of the dominant zonal tidal terms between 7 and 365 days. In contrast of the former kindred studies, we both address the discrepancy of the results brought by various EOP series and the hydro‐atmospheric corrections on the LOD. Our study forwards the complementary corrections brought by the ocean, the land water and sea level changes. Below 32 days, removing the atmospheric‐oceanic excitation from LOD allows to much better constraint the admittance complex coefficients κ than applying the atmospheric correction only: the discrepancy with respect to modeled values is reduced up to 70%, and the frequency dependence of the imaginary part brought by the ocean dynamical response is confirmed. A systematic effect with respect to the values modeled by Ray and Erofeeva (2014), https://doi.org/10.1002/2013jb010830 has been detected and hints a defect of this model. Moreover, the role of land water and associated sea level variation is notable at the semi‐annual period.

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An Analysis of Tidal Variations In the Length of Day

Cited by 14 publications

References 23 publications

Dynamic Ocean-Tide Effects On Earth's Rotation

Dynamic Ocean-Tide Effects On Earth's Rotation

Tidal variations in UT1 observed with very long baseline interferometry

Admittance of the Earth Rotational Response to Zonal Tide Potential

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