Diurnal Waves Research Articles

Numerical Modeling of Tidal Phenomena of the Penzhinskaya Bay

In this study, the Delft3D-Flow hydrodynamic model was used to determine the characteristics of the main tidal waves and currents in the Penzhina Bay (Sea of Okhotsk, Russia). The initial and boundary conditions are set according to the TPXO9 model data, the salinity and water temperature for each model layer are set based on the reanalysis data of the HYCOM ocean general circulation model, with a time step of 3 h. E-uropean Center for Medium-Range Weather Forecasts ECMWF (European Center for Medium-Range Weather Forecasts) reanalysis ERA-5 was used as meteoforcing. Modeling was performed for the ice-free period from May to September 2005. Maps of cotidal lines, tidal ellipses, and reversibility coefficient for the main tide waves: semidiurnal wave M2 and diurnal wave K1 were constructed. The model was verified by comparing the published and calculated harmonic components for 9 sea level monitoring points located in the Penzhina Bay. Conformance evaluation generally shows a high degree of consistency between model and reference data. The values of the coefficient of determination R2 between the series formed by the model and published harmonic components are in the range of 0.96–0.99. According to the magnitude of relative errors, the simulation results are divided into two consistency categories – high (1.48–2.14%) and satisfactory (2.93–4.27%). Spatial patterns of distribution for the values of relative errors were not found. A certain inconsistency in the results is presumably due to the time discretization of the observation time support and the short sea level monitoring data series used to calculate the published harmonic components at the Penzhina Bay.

Energetic Particle Precipitation Influence on Tidal Variations of Thermosphere Parameters in September 2017

The role of energetic particle precipitation in the formation of thermospheric tides is investigated. Using the Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere (GSM TIP) and two models of energetic particle precipitation, APM (Auroral Precipitation Model) and AIMOS 2.0.-AISstorm (Atmospheric Ionization Module Osnabrück 2.0—Atmospheric Ionization during Substorms), we performed simulations for the period 3–12 September 2017. This period covers both geomagnetically quiet days and the storm of 7–8 September. The analysis shows that migrating tides diurnal wave (DW) and semidiurnal wave (SW) prevail on quiet days for both versions of the simulations. On the day of maximum storm development on 8 September and the day after—9 September, the nonmigrating components of tidal waves, mainly DW0 and SW0, are intensified. There are also increasing differences in the spatial structure of tides between the two versions of simulations, especially between diurnal and semidiurnal tides at 154 km. On the disturbance days, the amplitudes of diurnal and semidiurnal tides at 154 km in the APM version are markedly greater than the corresponding values in the AIMOS version. Thus, it should be noted that the integral characteristics of the ionization function from precipitations are more important for the formation of DW and SW than its spatial structure or the features of temporal variations. A comparison of the total electron content (TEC) maps for the two versions of the simulation showed that the AIMOS version nicely reproduces the experimental data for a quiet time. The APM version is less accurate for quiet time but simulates the quantitative increase to disturbed conditions at high and middle latitudes better. For model reproduction of observed TEC variations at low and equatorial latitudes, it is not enough to consider the thermospheric source of thermospheric tides. In this case, the role of atmosphere–ionosphere coupling is very important.

Diurnal waves forced by horizontal convergence of near-surface winds on Mars

Boundary-layer winds near steeply sloped topography excite a distinct type of atmospheric wave. Basic properties of the waves were determined through analysis of 7 Mars years of temperature profiles from the Mars Climate Sounder on Mars Reconnaissance Orbiter. A more complete understanding of the waves was derived from a simulation with the NASA Ames Mars General Circulation Model. This type of wave appears in the tropics in the vicinity of conspicuous surface features, such as large volcanoes and the rim of Isidis Planitia. The amplitude is typically 5–10 K, the vertical wavelength is about 40 km, the zonal wavelength is about 1400 km, and the zonal phase speed relative to the surface is about 25 m s−1. The wave forcing comes from horizontal convergence of the near-surface winds, which generates a daily surge in the vertical winds. These convergence zones were not previously recognized as an important source of atmospheric waves on Mars. Strong forcing occurs only within a limited range of local time, producing wave packets (diurnal pulses) rather than steady oscillations. Waves are present throughout the year and their properties vary with season. Near the solstices, the wave amplitude is largest in the tropics of the summer hemisphere, where the convergence zones are stronger than in the winter hemisphere. The diurnal-mean zonal winds, which vary with latitude and season, control the direction of propagation of the predominant waves through filtering by critical levels.

Diurnal and semidiurnal internal waves on the southern slope of the Yermak Plateau

The Yermak Plateau (YP) is located across the Arctic–Atlantic gateway in the northwest of the Svalbard archipelago. In this region, internal waves are believed to cause intense turbulent mixing and hence influence the heat budget in the Arctic Ocean. Based on year-long observations from three moorings, the characteristics and energetics of diurnal and semidiurnal internal waves on the southern slope of the YP are investigated in this study. Diurnal internal waves induce large isothermal displacements exceeding 100 m, which are nearly one order of magnitude greater than those of semidiurnal internal waves. In addition, diurnal internal waves are strong in winter but weak in summer, while the semidiurnal internal waves exhibit complicated temporal variation. For the diurnal internal waves, their available potential energy is greater than the horizontal kinetic energy; whereas the situation is opposite for the semidiurnal ones. This feature is further clarified with two-dimensional numerical simulations. Due to the larger tidal excursion, diurnal tidal forcing yields the generation of stronger higher harmonics, i.e., the semidiurnal internal waves. In contrast, higher harmonics are rather weak under the semidiurnal forcing. Moreover, a large proportion of energy for both diurnal and semidiurnal internal waves is dissipated locally. Results of this study can provide useful insight on the dynamics of internal waves in the Arctic Ocean.

GABLS4 intercomparison of snow models at Dome C in Antarctica

Abstract. The Antarctic plateau, characterized by cold and dry weather conditions with very little precipitation, is mostly covered by snow at the surface. This paper describes an intercomparison of snow models, of varying complexity, used for numerical weather prediction or academic research. The results of offline numerical simulations, carried out during 15 d in 2009, on a single site on the Antarctic plateau, show that the simplest models are able to reproduce the surface temperature as well as the most complex models provided that their surface parameters are well chosen. Furthermore, it is shown that the diversity of the surface parameters of the models strongly impacts the numerical simulations, in particular the temporal variability of the surface temperature and the components of the surface energy balance. The models tend to overestimate the surface temperature by 2–5 K at night and underestimate it by 2 K during the day. The observed and simulated turbulent latent heat fluxes are small, of the order of a few W m−2, with a tendency to underestimate, while the sensible heat fluxes are in general too intense at night as well as during the day. The surface temperature errors are consistent with too large a magnitude of sensible heat fluxes during the day and night. Finally, it is shown that the most complex multilayer models are able to reproduce well the propagation of the daily diurnal wave, and that the snow temperature profiles in the snowpack are very close to the measurements carried out on site.

Effect of surface insulation on thermal stress of concrete

For concrete, the appearance of temperature load due to the hydration heat of cementitious materials is inevitable and important to the structural safety of dam. This paper investigates the effect of different surface insulation measures on the thermal stress of dam concrete by means of finite element simulation calculation. The calculation results show that surface insulation is important for lowering the surface thermal stress of concrete. When the equivalent surface coefficient of heat transfer was less than 3kJ/(m2·h·°C), the surface tensile stress can be decreased by 80%~90% for concrete undergoing diurnal temperature variation and cold wave.

Two Components of the Baric Tilt of Elements of the Earth Surface: the Case of a Low-Angle Topography

The effect of topography on variations in baric tilts is analyzed for several cases. The baric field is assumed to be equilibrium. This means that the horizontal component of the atmospheric pressure gradient is zero (wind is excluded). The case of 2D low-angle topography is investigated. The small parameter method invented by S.M. Molodenskii to estimate the effect of a low-angle topography on tidal tilts and deformations is used. This method gives an approximate analytical solution of the problem. It turns out that the baric tilt represents the sum of two terms, which have opposite signs as a rule. The first term depends on the pressure at sea level; the second is governed by the vertical pressure gradient. The baric tilt is calculated for two types of 2D topography: a secluded low-angle hill (an isosceles triangle with small base angle) and a plateau (a trapezoid whose height is small compared to the base). It is shown that for values of the geometric parameters and elastic modulus of the Earth’s core close to the real ones, variations of tilts caused by baric field variations may be comparable to the amplitude of diurnal tidal waves.

Automated detection of simultaneous/non-simultaneous Forbush decreases and the associated cosmic ray phenomena

The knowledge of the periodic diurnal anisotropy in the cosmic ray (CR) flux intensity as well as the enhanced anisotropy that might accompany Forbush events is not novel. Theoretical models and several methodological approaches such as Fourier techniques developed to predict the diurnal vectors started appearing in the literature since 1960s’. Consequently, the vectors have been successfully calculated on both annual, monthly and day to day basis. The amplitude and the phase of the unusually large diurnal wave trains that happen at the time of FDs have also been estimated by the method of Fourier analysis. However, direct application of Fourier transform algorithms to account for the enhanced CR diurnal anisotropies during the period of Forbush events is one of the open questions in CR research. Manual FD event identification technique, traditionally employed to select the short-term rapid depressions (Forbush decreases, FDs) in CR intensity is inefficient to handle the characteristic CR flux superposition tendencies. Identifications of FDs and the accompanying enhanced amplitude of the CR diurnal anisotropies are rarely investigated simultaneously. This poses a drawback on quantitative prediction of the impact of CR anisotropies on the detectable number of global and location dependent FDs as well as their magnitudes. A detailed and rigorous analysis involving simultaneous application of Fourier analysis to FDs and diurnal anisotropies, selections of FDs from Fourier transformed and raw CR data are attempted in the current work. The results are discussed with emphasis on simultaneity of FDs detected at different locations at Earth.

Discharge and water level fluctuations in response to flow regulation in impounded rivers: An analytical study

To analyze the hydrodynamics in an impounded river in response to discharge regulation at upstream and downstream dams, we developed a one-dimensional analytical model. The model provides analytical solutions for discharge and water level fluctuations along the river for periodic discharge boundary conditions at both dams. As a case study, the model was applied to a 38 km long section of the Yangtze River located between the Three Gorges Dam and Gezhouba Dam. The outflow discharge at both dams fluctuated diurnally due to varying demand of hydropower electricity during day and night. In good agreement with observational data, the model results showed significant diurnal variation of water level and discharge along the river. Using the model, we analyzed the sensitivity of the amplitude of diurnal fluctuation of water level and discharge to the parameters describing diurnal discharge regulation. Rapid discharge changes at the dams induced large amplitudes of diurnal variation of water level and discharge in the river. The amplitude of the diurnal wave in the river depends strongly on the lag time between discharge changes at both dams and was lowest if the lag time corresponded to the propagation time of a gravity wave along the river (0.6 h in the case study). In addition to the diurnal wave, high frequency waves were generated, with a period corresponding to the eigenperiod of the impounded river system (1.2 h in our case study). The standing wave is generated by rapid discharge changes at both dams and its amplitude is strongly dependent on the lag time between these changes. The high frequency eigenwave has little influence on water level variation but relative strong influence on discharge variation in the river.

Spectrum Response of LJ Well to Various Stresses During Non-seismic and Seismic Periods

The well water level in a deep well has significant frequency dependence on various crustal stresses, which can provide an effective pathway for determining the well-aquifer properties and investigating the response mechanism of groundwater. However, due to the limitations and complexity of the field conditions, there is a lack of on-site stress–strain data for rocks. Therefore, it is difficult to directly and quantitatively interpret the transfer response between the strain–stress and the well water level. The observation item data for the LJ well in China are relatively complete, including rainfall, barometric pressure, volumetric strain and deep water level data. By calculating the spectral period, spectral density, coherence function and transfer function of various physical variables, the spectrum response characteristics of the well-aquifer system to various stresses can be effectively obtained. When the crust is in a relatively stable state, the semidiurnal and diurnal waves are dominant. Moreover, the transfer functions of the well water level’s response to the theoretical semidiurnal and diurnal Earth tides and the barometric pressure are basically consistent with the correlation analysis results. In addition, when earthquakes occur, the signals of the volumetric strain and the well water level can more effectively highlight the relatively intermediate- and high-frequency information. The transfer function between the well water level and the volumetric strain is nearly an order of magnitude smaller than that in the stable state, indicating that the hydrogeological conditions of the LJ well-aquifer change instantaneously when subjected to seismic waves. All the above conclusions show that the correlation and transfer function based on spectral analysis is a feasible and advantageous method of determining the correlation of various physical variables. These results provide a foundation for further research on the hydrogeological characteristics of aquifers.

Martian Year 34 Column Dust Climatology from Mars Climate Sounder Observations: Reconstructed Maps and Model Simulations

AbstractWe have reconstructed longitude‐latitude maps of column dust optical depth (CDOD) for Martian year (MY) 34 (5 May 2017– 23 March 2019), using observations by the Mars Climate Sounder (MCS) aboard NASA's Mars Reconnaissance Orbiter spacecraft. Our methodology works by gridding a combination of standard (v5.2) and novel (v5.3.2) estimates of CDOD from MCS limb observations, using an improved “Iterative Weighted Binning.” In this work, we have produced four gridded CDOD maps per sol, at different Mars Universal Times. Together with the seasonal and daily variability, the use of several maps per sol also allows us to explore the diurnal variability of CDOD in the MCS dataset, which is shown to be particularly strong during the MY 34 equinoctial global dust event (GDE). In order to understand whether the diurnal variability of CDOD has a physical explanation, and examine the impact of the MY 34 GDE on some aspects of the atmospheric circulation, we have carried out numerical simulations with the “Laboratoire de Météorologie Dynamique” Mars Global Climate Model. We show that the model is able to account for at least part of the observed CDOD diurnal variability. This is particularly true in the southern hemisphere where a strong diurnal wave at the time of the GDE is able to displace dust horizontally as well as vertically. The simulations also clearly show the impact of the MY 34 GDE on the mean meridional circulation and the super‐rotating equatorial jet, similarly to the effects of the equinoctial GDE in MY 25.

The amplitudes and phases of tidal constituents from Harmonic Analysis at two stations in the Gulf of Aden

Amplitudes and phases of the tidal constituents are computed from harmonic analysis for the ports of Aden and Djibouti from the hourly Sea Level data for the year 2008 at these locations. The analysis shows that the tides are of mixed nature in the area. The ratio F = K1 + O1/M2 +S2 gives a value of 0.87 and 0.85 for Aden and Djibouti stations. The high astronomical tide and low astronomical tides are respectively 1.138 m and − 1.681 m for Aden port and 1.144 m and − 1.671 m for Djibouti port. Tidal amplitudes and phases at both stations are found closely similar. The major constituents of semi-diurnal waves are M2, S2 and N2 tides with amplitudes of 0.476, 0.215 and 0.129 m. The dominant diurnal waves are K1, O1 and P1 tides with amplitudes of 0.401, 0.201 and 0.121 m respectively. Other tidal constituents represented by third, fourth and sixth diurnal constituents, they have small amplitudes. In these groups, the M3, M4 are the major components with amplitudes of 0.005 m, 0.003 m respectively.

Continuous Detection of Diurnal Sodium Fluorescent Lidar over Beijing in China

Based on application of the atomic filter technology in a signal detection system of lidar, the diurnal observation of sodium lidar were obtained using the system at the National Space Science Center of the Chinese Academy of Sciences at Beijing Yanqing station (40.5° N, 116° E) in April 2014. During the lidar observation period, among the 103 cases of continuous daytime observations, the longest time was 181 h. In the case of a continuous observation period of 5 days (13–18 October 2014), the signal-to-noise ratio reached to 19:1 at 12:00–13:00 Local Time of the daytime, when the spatial and time resolutions were respectively set to 96 m of 167 s. The improvements resulted in the highest detection level of any existing diurnal lidars in China. Some interesting phenomena such as the sporadic sodium layer have also been observed during the daytime. The daytime capability extended the observing time range of the earlier systems that were limited to only nighttime observations. This innovation provides a useful method for the studies of diurnal tides, photochemistry, gravity waves, and correlative modeling studies.

Calculation of Tidal Displacements and Tilts for a Nonelastic Rotating Earth

A technique for calculating tidal displacements and tilts for the Earth both with the ocean and without it is presented in this work. This technique mainly follows the technique described in the International Earth Rotation Service Conventions and differs from it in small corrections in formulas for the calculation of displacements for diurnal (21) and semidiurnal (22) waves, as well as in an another set of usual and load Love numbers. Values of the gamma factors for the Earth without the ocean are also presented. Our results can be used for the processing of GNSS and tilt-measuring observations. The obtained results are compared with works by other authors, and the calculation technique is implemented in the new version of the ATLANTIDA3.1_2017 program for predicting parameters of Earth tides.

Observation of Enhanced Nonlinear Interactions After Severe Tropical Storm Chanchu (2004) in the Western South China Sea

AbstractSevere tropical storm Chanchu passed the subsurface mooring in the western South China Sea in June 2004, and its effects on the internal wavefield and nonlinear interactions were examined. The internal wavefield was characterized by diurnal (D1) and semidiurnal (D2) tides before Chanchu. However, after the passage of Chanchu, the internal wavefield was not only characterized by diurnal and semidiurnal tides but also by near‐inertial (f) waves, internal waves with higher harmonic frequency (fD2 = f+D2 and D3 = D1+D2), and enhanced diurnal currents. Analysis of the rotary coefficient and bicoherence suggested that the observed fD2 waves, D3 waves, and enhanced diurnal currents originated from the nonlinear interactions of f+D2 = fD2, D1+D2 = D3, and f+f = 2f, respectively. Previous studies indicated that the nonlinear interactions induced by tropical cyclones mainly occur between the near‐inertial waves and internal tides (f+D1 = fD1 or f+D2 = fD2). Our observations indicate that tropical cyclones can also induce the self‐interaction of near‐inertial waves (f+f = 2f) and enhance nonlinear interactions between diurnal and semidiurnal tides (D1+D2 = D3). Critical diurnal latitudes (where 2f ≈ D1) play an important role in the occurrence of these nonlinear interactions. Near‐inertial waves undergo self‐interactions (f+f = 2f) near the critical diurnal latitudes, and near‐inertial energy is transferred to diurnal waves. Enhanced diurnal waves further contribute to the nonlinear interactions of D1+D2 = D3. These nonlinear processes might promote the energy cascade of the near‐inertial waves induced by tropical cyclones near the critical diurnal latitudes and play an important role in ocean mixing.

Detection of free core nutation resonance variation in Earth tide from global superconducting gravimeter observations

In order to verify the time variability of free core nutation (FCN) period, global superconducting gravimeter (SG) observations were analyzed based on synthetic test data. The gravity data series were synthesized to check the detectability of resonance variation caused by FCN period change. The tests indicate that the discrepancy between the FCN periods determined by SG and VLBI observations is caused by the high correlation between the FCN parameter and the amplitude factor of the ψ1 wave. The K1 wave is more sensitive to the FCN period change than other diurnal waves. The limit of the standard deviation of the K1 wave is found for more precisely observing the FCN period change. Tidal parameters of diurnal waves estimated from long series of 20 global SG stations were analyzed. A common variation trend is found in the amplitude factor of both K1 and ψ1 waves in all 8 stations above the limit, which indicates the FCN period may be not so stable in time. Furthermore, the variation in the K1 and ψ1 waves constrains the FCN period change to between 2.5 and 4 sidereal days, which also agrees with the possible variation from the current VLBI and SG observations.

Behavior of Diurnal Internal Waves in the Southwestern East/Japan Sea

ABSTRACT Chae, J.-Y.; Jeon, C.; Park, S.J.; Choi, Y., and Park, J.-H., 2018. Behavior of diurnal internal waves in the southern East/Japan Sea. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 486–490. Coconut Creek (Florida), ISSN 0749-0208. The diurnal internal waves cannot freely propagate and are trapped near their generation site in the East/Japan Sea due to its sub-inertial environment. Previous studies show that diurnal internal shelf waves (ISWs) are generated around the southern Ulleung Basin (UB) with their energy concentrated there. To investigate the spatio-temporal variation of diurnal ISWs, we use a high-resolution numerical ocean model that is forced by realistic 16 tidal constituents and involves a data assimilation scheme. The baroclinic total energy and the conversion rate of barotropic to baroclinic energy show higher values at the southern s...

English

Studies have been done on the variability of cosmic rays flux during solar quiet days at mid and high latitudes. By using the 5 quietest days for each month, the monthly mean diurnal variation of cosmic ray anisotropy have been derived for the period 1981 to 2007, which covers part of cycles 21, 22 and 23. These quiet days are days during which the sun is relatively magnetically quiet, leading to less anisotropic behaviour in the diurnal flux of cosmic rays measured on the earth surface. Four stations (Rome, Oulu, Inuvik and Thule) were used in this study to understand the important features of the high latitude and mid-latitude diurnal wave, and how solar and geomagnetic activity may be influencing the wave characteristics. Cosmic ray wave characteristics were obtained by discrete Fourier transform (DFT). The mean, diurnal amplitude, phase and dispersion for each month's diurnal wave were calculated and profiled. There was clear indication that the terrestrial effect on the variability of the monthly mean of Cosmic ray count rates was more associated with geomagnetic activity rather than rigidity of the cosmic rays. Correlation of the time series of these wave characteristics (that is, amplitude and phase) with solar and geomagnetic activity index showed better association with solar activity. Key words: Cosmic rays, Fourier Transformation, solar quiet day, geomagnetic activity solar activity.

Results and analysis of the Earth’s tidal observations in the territory of Ukraine

1300 monthly series of continuous tiltmeter and gravimetric observations have been processed on 25 earth tide stations of Ukraine. High-precision regional parameters and of the main tidal waves, Love’s numbers and , differences of amplitude factors of diurnal tidal waves O 1 and K 1 have been received, which characterize the real physical properties and condition of the Earth’s core and promote a choice or construction of its most reliable model.

Factors influencing hydrogen flux in a fault zone of Henan Province, China

This research investigates the main factors influencing changes in hydrogen concentration in a fault zone and analyzes the relationship between hydrogen and tectonic activity. Based on the hydrogen concentration in the fault gas and continuous observation data from Mashankou, Neixiang County, Henan Province, the relationships between the variation in hydrogen concentration and ground temperature, atmospheric temperature, and atmospheric pressure are analyzed. In addition, the earth tide effect on hydrogen in the fault zone is discussed. The results show that the direct influence of atmospheric or ground temperatures on the hydrogen concentration is not significant. The atmospheric and ground temperatures have some impact on the hydrogen concentration only when ground temperature increases. By means of a wavelet analysis method, which separates the semidiurnal wave and diurnal wave signals of hydrogen, the results show that the hydrogen concentration is capable of indicating the solid earth tide when comparing the pressure tide and solid earth tide signals in the same period.