Analytical Calculations of Some Effects of Tidal Forces on Plants on the International Space Station

Among the phenomena attributable to the Moon’s actions on living organisms, one of them seems to be related to analytical fluid mechanics: along the route of the International Space Station around the Earth, experiments on plants have revealed leaf oscillations. A parametric resonance due to a short period of microgravitational forces could explain these oscillations. Indeed, Rayleigh-Taylor’s instabilities occurring at the interfaces between liquid-water and its vapor verify a second-order Mathieu differential equation. This is the case of interfaces existing in the xylem channels of plant stems filled with sap and air-vapor. The magnitude of the instabilities depends on the distances between the Moon, the Sun, and the Earth. They are analogous, but less spectacular, to those that occur during ocean tides.

Regional Evaluation of Minor Tidal Constituents for Improved Estimation of Ocean Tides

Satellite altimetry observations have provided a significant contribution to the understanding of global sea surface processes, particularly allowing for advances in the accuracy of ocean tide estimations. Currently, almost three decades of satellite altimetry are available which can be used to improve the understanding of ocean tides by allowing for the estimation of an increased number of minor tidal constituents. As ocean tide models continue to improve, especially in the coastal region, these minor tides become increasingly important. Generally, admittance theory is used by most global ocean tide models to infer several minor tides from the major tides when creating the tidal correction for satellite altimetry. In this paper, regional studies are conducted to compare the use of admittance theory to direct estimations of minor tides from the EOT20 model to identify which minor tides should be directly estimated and which should be inferred. The results of these two approaches are compared to two global tide models (TiME and FES2014) and in situ tide gauge observations. The analysis showed that of the eight tidal constituents studied, half should be inferred (2N2, ϵ2, MSF and T2), while the remaining four tides (J1, L2, μ2 and ν2) should be directly estimated to optimise the ocean tidal correction. Furthermore, for certain minor tides, the other two tide models produced better results than the EOT model, suggesting that improvements can be made to the tidal correction made by EOT when incorporating tides from the two other tide models. Following on from this, a new approach of merging tidal constituents from different tide models to produce the ocean tidal correction for satellite altimetry that benefits from the strengths of the respective models is presented. This analysis showed that the tidal correction created based on the recommendations of the tide gauge analysis provided the highest reduction of sea-level variance. Additionally, the combination of the EOT20 model with the minor tides of the TiME and FES2014 model did not significantly increase the sea-level variance. As several additional minor tidal constituents are available from the TiME model, this opens the door for further investigations into including these minor tides and optimising the tidal correction for improved studies of the sea surface from satellite altimetry and in other applications, such as gravity field modelling.

Impact of the stochastic model of the ocean tides on GRACE monthly gravity field solutions

<p><span>I</span><span>n </span><span>GRACE data </span><span>processing</span><span> </span><span>t</span><span>he geophysical </span><span>background </span><span>models, which are needed to compute </span><span>the </span><span>monthly gravity field solutions, </span><span>usually </span><span>e</span><span>nter as</span><span> error-free. </span><span>This</span><span> </span><span>means that model errors could influence and distort the gravity field solution</span><span>.</span></p><p><span>The geophysical models </span><span>which influence the solution the most</span><span> a</span><span>re</span><span> the </span><span>atmosphere and ocean dealiasing product (AOD1B) and the ocean tide model. </span><span>In this presentation we focus on the </span><span>ocean tide model and on incorporati</span><span>ng</span><span> </span><span>its </span><span>stochastic information </span><span>in data processing</span><span>. </span></p><p><span>We use </span><span>the FES2014 ocean tide model presented as a spherical harmonic expansion till degree and order 180. The information about its uncertainties and the correlations between different spherical harmonics is provided by the research unit NEROGRAV (New Refined Observations of Climate Change from Spaceborne Gravity Missions). In a first step, the stochastic properties of the tide model are considered to be static and are expressed as variance-covariance matrices (VCM) of the spherical harmonics of the 8 main tidal waves till degree and order 30. The incorporation of this stochastic information is done by setting up the respective ocean tide harmonics as parameters to be solved for. Since ocean tides cannot be freely estimated within monthly GRACE solutions, the provided VCMs for the 8 tidal waves are used for constraining the tidal parameters.</span></p><p><span>T</span><span>his procedure was used to compute monthly gravity field solutions for the year 2007. For a comparison, we computed also monthly gravity fields without taking into account the stochastic information on ocean tides. In this contibution we present and discuss the first results of this comparison.</span></p>

A high resolution three-dimensional model of ocean tides for the pan-arctic region

<p>As grid resolutions of operational ocean models are becoming finer and approach closer to the coast, the importance of inclusion of tidal forcing in high resolution operational ocean forecasting systems has increasingly been recognized. In the current work,  we present a 3D general ocean circulation model of ocean tides in the pan-Arctic region at ~3km horizontal grid resolution and 50 hybrid layers in the vertical, thus representing both barotropic and internal tides. The model system is based on the Hybrid Coordinate Ocean Model (HYCOM)  coupled with the Los Alamos Sea Ice Model (CICE). The results showed good agreement when compared with observations from tide gauges and a data-assimilative global barotropic tidal model. Among other results, the evaluation includes results for tidal amplitude and phase of the most energetic constituents (M2, S2, K1 and Q1).   The model system is currently operational and its development is supported by the Copernicus Marine Environment Monitoring Service (CMEMS) where its forecasts are disseminated.</p>

Direct measurements reveal instabilities and turbulence within large amplitude internal solitary waves beneath the ocean

Internal solitary waves are ubiquitous in coastal regions and marginal seas of the world’s oceans. As the waves shoal shoreward, they lose the energy obtained from ocean tides through globally significant turbulent mixing and dissipation and consequently pump nutrient-rich water to nourish coastal ecosystem. Here we present fine-scale, direct measurements of shoaling internal solitary waves in the South China Sea, which allow for an examination of the physical processes triggering the intensive turbulent mixing in their interior. These are convective breaking in the wave core and the collapse of Kelvin–Helmholtz billows in the wave rear and lower periphery of the core, often occurring simultaneously. The former takes place when the particle velocity exceeds the wave’s propagating velocity. The latter is caused by the instability induced by the strong velocity shear overcoming the stratification. The instabilities generate turbulence levels four orders of magnitude larger than that in the open ocean.

Changes in Homogeneous degree Caused by Marine Oil Spill

Based on the survey data of Jiaozhou Bay waters in May, September and October 1993, this paper studies the surface horizontal distribution of PHC content in Jiaozhou Bay waters. According to the definition, model and classification of Yang Dongfang homogeneity theory of matter content in waters proposed by the author, the calculation results show that in May, in the waters of Jiaozhou Bay, the non-homogeneous column of PHC content was 46.86μg/L, and the homogeneity of PHC content was 8.15%. At this time, the PHC content had non-homogeneity; in September, the non-homogeneous column of PHC content was 6.53μg/L, and the homogeneous was 48.58%, on which the PHC content had a low degree of homogeneity; in October, the non-homogeneous column of PHC content was 0.40μg/L, and the homogeneity was 96.61%, on which the PHC content had a high degree of homogeneity. This shows that in May, in the entire waters of Jiaozhou Bay, there was the only source of marine oil spill transportation, and the PHC content transported was 51.00μg/L, which was relatively high, resulting that the PHC content was unevenly distributed in the entire water body in the bay. In September, in the entire waters of Jiaozhou Bay, there was only the source of marine oil spill transportation, and its PHC content was 12.70μg/L, which was relatively low. In this way, the distribution of PHC content in the entire water body was lowly homogeneous. In October, there was no source of PHC content in the bay, and the PHC content was relatively low. In this way, the distribution of PHC content in the entire water body was highly homogeneous. From May to September, the monthly decline rate of the PHC content from marine oil spill was 9.57μg/L, the monthly decline rate of the non-homogeneous column of PHC content was 10.08μg/L, and the monthly increase rate of the homogeneity of PHC content was 10.10%. From September to October, the monthly decline rate of the PHC content of marine oil spill was 12.70μg/L, the monthly decline rate of the non-homogeneous column of PHC content was 6.13μg/L, and the monthly increase rate of the homogeneity of PHC content was 48.03%. This fully reveals that the PHC content of marine oil spill is the driving force of its non-homogeneity in the water area, while the ocean tides and currents are the driving force of its homogeneity in the water area. Based on this, the author puts forward the theory of homogeneous distribution of material content: under the action of ocean tides and currents, the ocean has the characteristics of homogeneity, and the distribution of material content in the ocean water body shows homogeneity.