Gravitational atmospheric tides as a probe of Titan’s interior: application to Dragonfly

<p>Just as Saturn’s massive gravity causes tides both in Titan’s interior as well as its surface seas, it causes a tide in the atmosphere (Lorenz 1992; Tokano & Neubauer 2002). Previous modelling work with a 3D Global Climate Model found that gravitational tides should produce a surface pressure variation of ∼1.5 hPa through the orbit of Titan and tidal winds in the troposphere (Tokano & Neubauer 2002). Here, we revisit gravitational atmospheric tides on Titan with analytical calculations and with a 3D Global Climate Model (the IPSL-Titan GCM). We show that the surface pressure field quickly adjust to the tidal potential, strongly decreasing the amplitude of tidal winds. We analyze the impact of the deformation of Titan’s interior and crust on the amplitude of the tidal pressure variations. Finally, we discuss how measurements of pressure variations by Dragonfly could help to constrain Titan’s interior and crust.</p>

On the permanent tide and the Earth dynamical ellipticity

<p>As other relevant quantities related to the Earth dynamics, the Earth dynamical ellipticity is influenced by tidal effects. In particular, it is affected by the permanent tide due to the time independent part of the Earth redistribution tidal potential. Hence, it is necessary to distinguish between its tide-free and non tide-free values (e.g., Burša 1995) when determining it from observations (e.g., Marchenko & Lopushanskyi 2018). This question is seldom considered in Earth rotation studies. For example, neither IAU2000/AIU2006 nutation/precession model nor IERS Conventions specify explicitly whether the dynamical ellipticity is a zero-tide parameter or not. However, current accuracy goals might be sensitive to that difference.</p><p>Within the framework of a Hamiltonian approach (Baenas, Escapa, & Ferrándiz 2019), we present a consistent treatment of the influence of the permanent tide on the dynamical ellipticity. In particular, we develop an analytical expression of the redistribution tidal potential based on Andoyer canonical variables and a semi-analytical theory of the orbital motions of the Moon and the Sun, following the same procedure as that given in Kinoshita (1977).</p><p>This method allows obtaining an expression of the zero frequency term of the redistribution tidal potential that updates that of Zadro & Marussi (1973), usually employed in reporting parameters of common relevance to Astronomy, Geodesy, & Geodynamics (e.g., Burša 1995, Groten 2004). In addition, it clarifies the procedure that must be followed in order that the dynamical ellipticity, fitted to the observations, contains the effects of the permanent tide avoiding in this way potential inconsistencies.</p>

The global distribution of the M1 ocean tide

The worldwide distribution of the small degree-3 M1 ocean tide is investigated using a quasi-global data set of over 800 tide gauge records and a global tide model. M1 is confirmed to have a geographical variation in the Atlantic consistent with the suggestion of Platzman (1984b) and Cartwright (1975) that M1 is generated in the ocean as a consequence of the spatial and temporal overlap of M1 in the tidal potential and one (or at least a small number of) diurnal ocean normal mode(s). As a consequence, it is particularly strong around the UK and on North Sea coasts (amplitudes ∼10 mm). This analysis shows that their suggestion is also consistent to a great extent with the observed small amplitudes in the Pacific and Indian oceans. However, there are differences at the regional and local level which require much further study via more sophisticated ocean tidal modelling. By contrast, what is called the M1' tide (a combination of several degree-2 lines in the tidal potential with frequencies close to that of M1) is shown to have a geographical distribution consistent with expectations from other degree-2 diurnal tides, apart from locations such as around the UK where tidal interactions introduce complications. As far as I know, this is the first time that these small tidal constituents have been mapped on a global basis and, in particular, the first time that the ocean response to the degree-3 component of the tidal potential has been investigated globally.

The global distribution of the M1 ocean tide

The worldwide distribution of the small degree-3 M1 ocean tide is investigated using a quasi-global data set of over 800 tide gauge records and a global tide model. M1 is confirmed to have a geographical variation in the Atlantic consistent with the suggestion of Platzman and Cartwright that M1 is generated in the ocean as a consequence of the spatial and temporal overlap of M1 in the tidal potential and one (or at least a small number) of diurnal ocean normal modes. As a consequence, it is particularly strong around the UK and on North Sea coasts. This analysis shows that their suggestion is also consistent to a great extent with the observed small amplitudes in the Pacific and Indian Oceans. However, there are differences at the regional and local level which require much further study via more sophisticated ocean tidal modelling. By contrast, the M1' tide is shown to have a geographical distribution consistent with expectations from other degree-2 diurnal tides, apart from locations such as around the UK where tidal interactions introduce complications. As far as we know, this is the first time that these small tidal constituents have been mapped on a global basis and, in particular, the first time that the ocean response to the degree-3 component of the tidal potential has been investigated globally.

Potensi Pasang Surut Lahan Rawa untuk Pengembangan Irigasi di Kabupaten Merauke Menggunakan Pemodelan Hidrodinamika 1D2D

Merauke Regency has three major rivers i.e Bian River, Kumbe River and Maro River (BIKUMA), the three rivers have large horizontal tidal potential. To know the potential of tides in the development of lowland irrigation in Merauke Regency needs to be studied. This study is supported by hydrometry and hydraulic surveys which has been conducted during the dry season during at spring tide and neap tide simultaneously for all three rivers. The survey included measuring river geometry activities with a range of 5 Km, river hydrometry measurements (observation of water fluctuations with proportional distances for model calibration and upstream river velocity for discharge). Limitations of river upstream measurements are limited by the distance where the Bian River along 125 Km, the River Kumbe along 171 km, and the Maro River along 66 km from the estuary. Then, performed a Sobek 1D hydrodynamic modeling that describes the movement of water from upstream into downstream. From the results of modeling is known that the water entering from the sea to the Bikuma River is greater than the water out to sea. The potential for tides is 1.7 Billion m3. Furthermore, the simulation of Sobek 1D2D to obtain the extent of natural condition, the area that can be inundated is 123.609 ha. Utilization of tidal potential can be channeled to the development zone through an integrated lowland irrigation water management system so that water utilization can be optimal.

A Study on Tidal Potential and Tide Generating Force

This study deals with the derivation of tidal potential and tide generating forces. Tidal potential is derived from the gravitational attraction of masses of the moon and the sun and from this potential tide generating forces are derived taking its horizontal gradients.GANIT J. Bangladesh Math. Soc.Vol. 37 (2017) 29-37

From regional to local scale modelling on the south-eastern Brazilian shelf: case study of Paranaguá estuarine system

The applicability of a numerical model following a downscaling methodology was evaluated for the south-eastern Brazilian shelf (regional model) and Paranaguá estuarine system (local model). This approach permits the simulation of different scale processes, such as storm surges and coastal upwelling, and is suitable for operational forecasting purposes. When large areas are covered by regional models, the tidal propagation inside the domain can be significantly affected by the local tidal potential, mainly where the resonance phenomenon is observed. The south-eastern Brazilian shelf is known for the resonance of the third-diurnal principal lunar tidal constituent (M3), the largest amplitudes being found in the Paranaguá estuarine system. Therefore, the significance of the local tidal potential was assessed in this study for the most important tidal constituents inside the estuarine system (including M3). The model validation was performed with tidal gauge data, Argo float profiles and satellite measurements of Sea Surface Temperature. The methodology described in this study can be replicated for other important estuarine systems located on the south-eastern Brazilian shelf. Furthermore, the numerical model was developed within a perspective of operational nowcast/forecast simulations, useful for several activities such as navigation and response to emergencies (e.g., oil spills).

The Tidal Potential of a Homogeneous Torus with an Elliptical Section of the Sleeve

In this paper the problem of the tidal potential of a homogeneous gravitating torus with an elliptical cross-section sleeve is solved. In particular, the potentials in analytical form in the vicinity of the center of the torus and its external region are found. This torus can serve as a gravitational model of the Kuiper belt.