Solid earth tide and Arctic oceanic loading tide at Longyearbyen (Spitsbergen)

The three components of the indirect oceanic effect are calculated for the M ₂, K ₁ and O ₁ waves and compared with the observed earth tide. The vertical component of the near Arctic oceanic load explains fairly well the large 45° observed phase lag of M ₂. The results for the horizontal components are satisfactory; the discrepancies between different tiltmeters are not due to the oceanic perturbations (unless some local or cavity effects are supposed).     

On the asymmetric diurnal tide

Summary The response of the atmosphere to a diurnally oscillating thermal drive, asymmetric with respect to the equator, is investigated. It is found that the solutions ofLaplace's tidal equation do not form a complete set; all of them being orthogonal to the associated Legendre polynomial,P ₂ ¹ (cos ), being the latitude. As an extension ofLaplace's theorem for gravitationally excited ocean tides to thermally driven atmospheric tides, it is shown that a diurnal drive whose latitude dependence is given byP ₂ ¹ gives rise to no surface pressure oscillation.     

固体潮的地震预测研究与地球动力学研究之分析比较

本文分析了现行固体潮地震研究中的历史影响,对比研究了固体潮地震预测研究和固体潮地球动力学研究二者在振动频率、振动源体积、传输距离与介质等方面的地球物理特点与本质区别,强调了固体潮地震预测研究中最根本的工作是建立地震预测的目标和基本概念.     

The lunar tide in sporadic E

It seems that the wind shear theory is accepted for the explanation of sporadic E at mid and low latitudes. Some examples from Arecibo are displayed to show this. The effect of lunar tides should then modify the wind-shear theory in a manner that yields the observed features of the lunar tide in the critical frequency foEs and the height h′Es of the sporadic E. This is shown to imply that the phase of the lunar tide in h’Es should be the same as the phase of the lunar tide in the eastward wind and that the phase of the lunar tide in foEs is three hours later. Hourly values of foEs, fbEs (the blanketing critical frequency) and h′Es from several observatories are analysed for the lunar semidiurnal tide. It is found that the phase of the tide in foEs is often about 3 hours later than for h′Es in agreement with the theory. Seasonal variations in the tide are also examined with the statistically most significant results (largest amplitudes) usually occurring in summer. After reviewing the many difficulties associated with determining the lunar tide in Es, both experimentally and theoretically, the analysed phase results are compared with what might be expected from Hagan’s global scale wave model. Agreement is only fair (a success rate of 69% among the cases examined) but probably as good as might be expected.     

Assessing the relative contributions of the flood tide and the ebb tide to tidal channel network dynamics

Flood and ebb currents provide different contributions to the initiation and evolution of tidal channel networks, generating diverse network structures and channel cross-sections. In order to separate the effects of these contributions, a physical model of a sloping tidal-flat basin was set up in the laboratory. Depending on the degree of tidal asymmetry imposed offshore, either flood or ebb currents can be enhanced. The experimental results show that the ebb current has a higher capability to initiate and shape tidal networks than the flood current. Headward erosion is mainly induced by the ebb flow. The slightly inclined flat surface tends to reduce the energy of the flood current and to enhance the ebb current, thus prolonging the duration of morphodynamic activity as well as sediment motion. Overall, flood-dominated tides favour the formation of small-scale channel branches in the upper basin zone, while long lasting ebb-dominated tides result in more complex, wider and deeper tidal networks. © 2019 John Wiley & Sons, Ltd.     

The lunar tide in theE-layer above Istanbul

Summary The lunar tide in theE-layer of the ionosphere above Istanbul has been determined by the analysis of thefo E parameter from 1964–1967. Semi-diurnal variations were found to be significant. The seasonal and monthly variations of the amplitude and phase of the lunar tide show very little differences.     

The lunar barometric tide in New Zealand

The lunar barometric tide has been determined with reasonable accuracy, on an annual and seasonal basis, at five stations on the mainland of New Zealand and at three of the outlying islands. The determinations show that in the New Zealand region the lunar tide has a larger amplitude and smaller phase than might have been expected from previously available southern-hemisphere results. In general, the seasonal variation of phase in the New Zealand region conforms to the currently recognised global pattern, with the J-season phase greater than that of the D-season. Similarly, the amplitude variation tends to support the suggestion that, south of latitude 30°S, the D-season amplitude is greater than that of the J-season. Approximate tests are introduced and used to assess the statistical significance of some of the apparent differences in amplitude and phase made evident by the analysis. These assessments indicate that although many of the apparent differences may be attributed to sampling fluctuations, the main regional anomalies in amplitude and phase are likely to be real. It is suggested that these anomalies may indicate a significant regional input of tidal energy to the atmosphere (at the lower boundary) from the Pacific oceanic tide.     

Ocean tide height calculation — Horizontal forces

Summary If the inadequacies of the classical ocean tide theory are acknowledged, it is appropriate to seek modifications of the usual formulation with a view to calculations in better agreement with the behavior of the observed heights. One long-standing objection is the total neglect of the horizontal components of fluid forces. By considering the total forces acting on the entire tidal layer in the same manner that is customary in the so-called momentum integral analysis of viscous boundary layers, it is shown that horizontal forces account for a tidal distortion identical to that usually attributed to the vertical forces. An interesting feature of the calculation is that results are obtained from the force balance directly, without the standard but somewhat obscure integration that is employed when the vertical forces are studied.     

27.3-day and 13.6-day atmospheric tide

An analysis of time variations in the earth's length of day (LOD) for 25 years (1973-1998) versus at- mospheric circulation changes and lunar phase is presented. It is found that, on the average, there is a 27.3-day and 13.6-day period oscillation in global zonal wind speed, atmospheric geopotential height, and LOD following alternating changes in lunar phase. Every 5-9 days (6.8 days on average), the fields of global atmospheric zonal wind and geopotential height and LOD undergo a sudden change in rela- tion to a change in lunar declination. The observed atmospheric oscillation with this time period may be viewed as a type of atmospheric tide. Ten atmospheric tidal cases have been analyzed by comparing changes in LOD, global zonal wind speed and atmospheric geopotential height versus change in lunar declination. Taken together these cases reveal prominent 27.3-day and 13.6-day tides. The lunar forcing on the earth's atmosphere is great and obvious changes occur in global fields of zonal wind speed and atmospheric geopotential height over the equatorial and low latitude areas. The driving force for the 27.3-day and 13.6-day atmospheric tides is the periodic change in lunar forcing during the moon's revolution around the earth. When the moon is located on the celestial equator the lunar declination equals zero and the lunar tidal forcing on the atmosphere reaches its maximum, at this time the global zonal wind speed increases and the earth's rotation rate decreases and LOD increases. Conversely, when the moon reaches its most northern or southern positions the lunar declination is maximized, lunar tidal forcing decreases, global zonal wind speed decreases, earth's rotation rate increases and LOD decreases. 27.3-day and 13.6-day period atmospheric tides deserve deeper study. Lunar tidal forcing should be considered in models of atmospheric circulation and in short and medium range weather forecasting.     

The role of earth tide in crustal movement

The earth tide is usually ignored in orogenesis (geosynclinal activity) and magmatic activity. We believe that the role of earth tide in crustal movement should not be ignored. The elemental dynamic analysis of origin of magma chamber under dissipative tidal heating model and orogenic process driven by alternating earth tidal force is depicted. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 508–513, 1993. Xue-Min AI and Liang CHI also worked for this project. This work was supported by the Laboratory of Dynamical Geodesy, Academia Sinica. Translated from Chinese into English by Liang CHI.     

近海潮汐效应对测站位移的负荷影响

利用TPXO6全球海潮模型和中国东海和南海潮汐资料研究了近海潮汐效应对我国沿海部分台站负荷位移的影响.结果表明,近海效应对位移的水平和垂直分量的影响均达到了mm的量级,其中在厦门站的影响最大,水平和垂直分量的振幅分别接近3 mm和15 mm,因此近海潮汐效应是沿海地区GPS动力学应用中应该考虑的负荷效应中的一个因素.另外,各台站负荷位移水平分量随时间变化的规律是不一样的,最大值对于不同的台站出现在不同的方位,并且对于垂直分量,在上海站和在其他沿海站的影响存在着明显的反相关系.本文结果可为GPS资料处理提供有益参考.     

长周期潮汐与全球地震能量释放

采用1850-2012年期间USGS全球M≥5.0地震目录资料,构成全球地震能量-时间序列,进行小波变换和准周期分析. 结果表明,全球地震能量释放的时间序列存在9年、19年和45年的3个准周期,其中,45年准周期最为突出. 结合起潮力周期的物理背景,对长周期潮汐起潮力与地震能量释放准周期的关系进行了探讨,没有发现全球地震活动的能量释放与潮汐短周期相关的准周期.     

Correlation between lunar node tide and great earthquakes

This study selects six consecutive 18.6 years of global M ≥ 7.0 earthquakes, calculates the lunar declination angle based on the time of the earthquakes, and di...