Atmospheric Tides Research Articles

High-altitude water ice cloud formation on Mars controlled by interplanetary dust particles

Submicrometre-size meteoric smoke aggregates form when interplanetary dust particles ablate and re-coagulate in the Martian atmosphere. The MAVEN (Mars Atmosphere and Volatile Evolution) satellite has detected pervasive ionized metallic layers due to meteor ablation at an 80–90 km altitude, which suggests a continuous supply of meteoric smoke particles that settle to lower altitudes. Until now, meteoric smoke has been neglected in general circulation model studies of the formation of Martian water ice clouds. Here we show that when meteoric smoke is included in simulations of the atmospheric circulation on Mars, mesospheric water ice clouds form at low pressures and in discrete layers, polar hood clouds extend to higher altitudes and the seasonal Hadley cell is weakened. Furthermore, we find that the middle atmosphere water ice clouds respond to and influence the diurnal and semidiurnal migrating thermal tides. We conclude that Mars atmospheric simulations that neglect meteoric smoke do not reproduce the observed spatial distribution of water ice clouds and miss crucial radiative impacts on the overall atmospheric dynamics. Particles from interplanetary dust ablating in Mars’ atmosphere control high-altitude water ice cloud formation, according to numerical simulations of the Martian atmosphere.

Utilizing the Impact of Earth and Atmospheric Tides on Groundwater Systems: A Review Reveals the Future Potential

AbstractGroundwater extraction is increasing rapidly in many areas of the world, causing serious impacts such as falling water tables, ground surface subsidence, water quality degradation, and reduction of stream baseflow on which many ecosystems depend. Methods for understanding and predicting the impacts of groundwater extraction generally lack detailed spatial and temporal knowledge of the subsurface hydrogeomechanical properties. This review provides a comprehensive understanding of Earth and atmospheric tides and their impact on subsurface pore pressure. First, we evaluate the global occurrence of Earth and atmospheric tides. Then, we illustrate their impact on the groundwater response and connect this with the theory of poroelasticity, which underpins quantitative analyses. Finally, we review methods that utilize these impacts to characterize groundwater systems and to quantify their hydrogeomechanical properties. We conclude by highlighting their potential as passive and low‐cost investigation techniques and by outlining the research and developments required to progress and make analyses readily available. Thus, hydrogeomechanical properties of subsurface systems could be obtained at unprecedented spatial and temporal resolution, adding additional value to commonly acquired groundwater and atmospheric pressure data.

Impact of Data Assimilation on Thermal Tides in the Case of Venus Express Wind Observation

AbstractImpacts of horizontal winds assimilation on thermal tides are investigated by using the Venus atmospheric general circulation model for the Earth Simulator local ensemble transform Kalman filter data assimilation system. The assimilated data are horizontal winds derived from Venus ultraviolet images taken by the Venus Monitoring Camera onboard the Venus Express orbiter. The results show that three‐dimensional structures of the thermal tides are significantly improved not only in the horizontal winds but also in the temperature field, even though the observations are available only at the cloud top level on the southern dayside hemisphere approximately once an Earth day. The reproduced temperature fields agree well with recent radio occultation measurements of the Venus Climate Orbiter Akatsuki. The zonal mean fields of the zonal wind and temperature are also improved globally. This study would enable reanalysis of past Venus observations.

Atmospheric and human‐induced impacts on temporal variability of water level extremes in the Taihu Basin, China

AbstractUnderstanding the variation of water level extremes with their potential drivers can provide insights for flood risk management. In this study, temporal variability of water level extremes is investigated across the plain river network region of the Taihu Basin. The driving force analysis on water level extremes is mainly conducted for atmospheric (rainfall, climatic index, and tide) and anthropogenic forcing. The quantile perturbation method is employed to examine variability of extreme values and the Spearman correlation analysis to identify potential drivers of extreme water level variability. Considering water level extremes in all seasons, the 1990s have statistically significant positive anomalies, while the late 1960s to the 1970s and the 2000s have significant negative anomalies. The oscillation pattern of anomaly in summer has a higher variability than that in the other three seasons. Significant correlations are detected between the anomalies of water level extremes and rainfall (tide level) during summer and winter. Water level extremes in summer and winter have a strong connection to the Pacific Decadal Oscillation and North Atlantic Oscillation/Arctic Oscillation, respectively. Conversely, no consistent significant correlations between water level extremes and climatic indices are found in spring and autumn, which is mainly related to hydraulic structure construction and operation.

Documentation of the NASA/Ames Legacy Mars Global Climate Model: Simulations of the present seasonal water cycle

We describe and document the physics packages in the legacy NASA/Ames Mars Global Climate Model, present simulations of the seasonal water cycle and how it compares with observations, assess the role of radiatively active clouds on the water cycle and planetary eddies, and discuss the strengths and weakness of the model and the implication for future efforts. The physics packages we describe include the treatment of surface properties, the ground temperature model, planetary boundary layer scheme, sublimation physics, cloud microphysics, the use of a moment method for tracer transport, a semi-interactive dust tracking scheme, and a two-stream radiative transfer code based on correlated-k's. With virtually no tuning of the water cycle and assuming the north polar residual water ice cap is the only source of water we find the model gives a reasonably good simulation of the present seasonal water cycle. No persistent clouds form over the residual cap, seasonal variations in column vapor abundances are similar to those observed, the aphelion cloud belt has about the right opacity, and surface and air temperatures are in reasonably good agreement with observations. The radiative effect of clouds does not significantly alter the seasonal and spatial variation of the moisture fields, though the clouds are thicker and the atmosphere somewhat wetter. As others have found cloud radiative forcing amplifies the mean meridional circulation, transient baroclinic eddies, and global thermal tides. However, it also changes the characteristics of forced stationary waves in ways that are not straightforward to understand. The main weakness of the model, we believe, is sluggish vertical mixing. Water is not transported high enough in the model and as a consequence the water cycle is too dry, the aphelion cloud belt is too low, and the mean meridional circulation is too shallow. These, we feel, could be remedied by some combination of non-local mixing, deep mountain-induced circulations, better horizontal and vertical resolution, and/or gravity wave drag. Efforts are now underway to study these issues as we are transitioning away from our legacy code to one with a more modern dynamical core.

Mesospheric anomalous diffusion during noctilucent cloud scenarios

Abstract. The Andenes specular meteor radar shows meteor trail diffusion rates increasing on average by about 10 % at times and locations where a lidar observes noctilucent clouds (NLCs). This high-latitude effect has been attributed to the presence of charged NLC after exploring possible contributions from thermal tides. To make this claim, the current study evaluates data from three stations at high, middle, and low latitudes for the years 2012 to 2016 to show that NLC influence on the meteor trail diffusion is independent of thermal tides. The observations also show that the meteor trail diffusion enhancement during NLC cover exists only at high latitudes and near the peaks of NLC layers. This paper discusses a number of possible explanations for changes in the regions with NLCs and leans towards the hypothesis that the relative abundance of background electron density plays the leading role. A more accurate model of the meteor trail diffusion around NLC particles would help researchers determine mesospheric temperature and neutral density profiles from meteor radars at high latitudes.

A Modified Nonstationary Tidal Harmonic Analysis Model for the Yangtze Estuarine Tides

AbstractInfluenced by river discharge, the tidal properties of estuarine tides can be more complex than those of oceanic tides, which makes the tidal prediction less accurate when using a classical tidal harmonic analysis approach, such as the T_TIDE model. Although the nonstationary tidal harmonic analysis model NS_TIDE can improve the accuracy for the analysis of tides in a river-dominated estuary, it becomes less satisfactory when applying the NS_TIDE model to a mesotidal estuary like the Yangtze estuary. Through the error source analysis, it is found that the main errors originate from the low frequency of tidal fluctuation. The NS_TIDE model is then modified by replacing the stage model with the frequency-expanded tidal–fluvial model so that more subtidal constituents, especially the “atmospheric tides,” can be taken into account. The results show that the residuals from tidal harmonic analysis are significantly reduced by using the modified NS_TIDE model, with the yearly root-mean-square-error values being only 0.04–0.06 m for the Yangtze estuarine tides.

Atmospheric Tides at High Latitudes in the Martian Upper Atmosphere Observed by MAVEN and MRO

AbstractGlobal‐scale waves have been seen throughout the Martian atmosphere and can achieve significant amplitude at higher altitudes. Previous observations of the upper atmosphere have also revealed wavenumber‐3 signatures with significant amplitudes that have been interpreted as signatures of diurnal and semidiurnal tides or stationary planetary waves. This study focuses on two intervals during which concurrent observations of the upper thermosphere made in situ, the middle thermosphere made remotely, and the middle atmosphere made remotely provide observations of the atmospheric tides between 50‐ and 200‐km altitude. Focusing on high latitudes, these observations are able to identify strong wavenumber‐3 signatures in the thermosphere that propagate eastward with increasing local time, consistent with an eastward propagating tide. A complementary analysis of the data from the middle atmosphere reveals wavenumber‐3 signatures that move eastward and upward. During the first interval, these analyses reveal a combination of the diurnal tide DE2 and the semidiurnal tide SE1 to be present, while during the second only the semidiurnal SE1 is seen. During both intervals, the observations provide a consistent picture of these waves being present from the middle atmosphere to the upper thermosphere, consistent with the theory that such waves are generated in the lower atmosphere and propagate upward throughout the entire atmosphere.

Generic frequency dependence for the atmospheric tidal torque of terrestrial planets

Context. Thermal atmospheric tides have a strong impact on the rotation of terrestrial planets. They can lock these planets into an asynchronous rotation state of equilibrium. Aims. We aim to characterize the dependence of the tidal torque resulting from the semidiurnal thermal tide on the tidal frequency, the planet orbital radius, and the atmospheric surface pressure. Methods. The tidal torque was computed from full 3D simulations of the atmospheric climate and mean flows using a generic version of the LMDZ general circulation model in the case of a nitrogen-dominated atmosphere. Numerical results are discussed with the help of an updated linear analytical framework. Power scaling laws governing the evolution of the torque with the planet orbital radius and surface pressure are derived. Results. The tidal torque exhibits (i) a thermal peak in the vicinity of synchronization, (ii) a resonant peak associated with the excitation of the Lamb mode in the high frequency range, and (iii) well defined frequency slopes outside these resonances. These features are well explained by our linear theory. Whatever the star–planet distance and surface pressure, the torque frequency spectrum – when rescaled with the relevant power laws – always presents the same behaviour. This allows us to provide a single and easily usable empirical formula describing the atmospheric tidal torque over the whole parameter space. With such a formula, the effect of the atmospheric tidal torque can be implemented in evolutionary models of the rotational dynamics of a planet in a computationally efficient, and yet relatively accurate way.

Meteorological Scale Correlation Relationship of the Ionospheric Longitudinal Structure Wavenumber 4 and Upper Atmospheric Daily DE3 Tide

AbstractIn order to analyze the relationship between atmospheric tides and the ionospheric day‐to‐day variations, this paper mainly presents the meteorological scale (period is shorter than 60 days) correlation relationship between the daily longitudinal structure wavenumber 4 (WN4) in the ionosphere and the daily diurnal eastward propagating with zonal wavenumber 3 (DE3) tide in the upper atmosphere. We deduce the latitudinal integration of total electron content from the global ionospheric maps in the middle‐ to low‐latitude ionosphere and the upper atmospheric temperature from Thermosphere‐Ionosphere‐Mesosphere Energetics and Dynamics\Sounding of the Atmosphere using Broadband Emission Radiometry observations in the MLT region. Applying new techniques proposed by Li et al. (2015, https://doi.org/10.1002/2015JA021577), we extract the daily WN4 structure and daily DE3 tide, respectively. We found that (1) the meteorological scale cross‐correlation coefficients are symmetric about the equator and dominate at the low latitudes; (2) there is a remarkable valley value around sunrise: the amplitudes in day time are a little larger than those at night; the phases in day time are stable and change slowly at night and dramatically before dawn; (3) they vary gradually with altitudes, and the vertical propagating wavelength is about 35‐km altitude; (4) they present an obvious annual variation that the amplitudes are larger from June solstice to early north autumn, and the phases are stable in these months; and (5) they display an obvious quasi‐biennial oscillation phenomenon, and in June to August of 2008–2009 the amplitudes almost disappear before dawn.

Fully Developed Superrotation Driven by the Mean Meridional Circulation in a Venus GCM

AbstractFully developed superrotation is reproduced for the first time in very long term simulations with a dynamical Venus general circulation model (GCM) driven by a zonally averaged component of the realistic solar heating only. Starting from a motionless state with temperature distribution including a low static stability layer in the lower cloud layer, the fast superrotating zonal flow of ~100 m/s is established after 500 Earth years. In this experiment, the mean meridional circulation is responsible for generating the superrotation, because effects of thermal tides, topography, radiation process, and cloud physics are excluded in the present simulations. Sensitivity experiments indicate that the vertical eddy viscosity smaller than 0.02 m2/s is necessary for the fast superrotation to appear. The low static stability layer also strongly affects the superrotation with high‐latitude jets through angular momentum transport by baroclinic/barotropic instability in the cloud layer.

Features of atmospheric tide according to the Geophysical observatory Mikhnevo

Atmospheric tides refer to those oscillations in the atmosphere whose periods are integral fractions of a lunar or solar day. Atmospheric tides are, in small measure, gravitationally forced, they are primarily forced by daily variations in solar insolation. Based on the results of instrumental observations of micropulsations of atmospheric pressure, the main waves of the lunar-solar tide in the Earth’s atmosphere are identified. The registration of micropulsations is obtained in the range from 0.1 MHz to 10 Hz in the Geophysical observatory Mikhnevo of Institute of Geosphere Dynamics of Russian Academy of Sciences located in the Moscow region in period 2008-2016. An estimate of the spectral characteristics of micropulsations was carried out using the maximum entropy method. In order to increase the level of discrimination related to the frequencies of tidal waves, the adaptive rejection filtering method was applied. It is shown that the spectral amplitudes with frequencies that coincide with the frequencies of the tidal waves change with time with a periodicity of about 29 days. The characteristics of modulation of the solar elliptic wave S1 and the main solar wave S2 by periods of 13.66, 27.55 days are obtained; as well as ∼ 0.3, 0.5 and 1 year.

Atmospheric tides and their consequences on the rotational dynamics of terrestrial planets

Atmospheric tides can have a strong impact on the rotational dynamics of planets. They are of most importance for terrestrial planets located in the habitable zone of their host star, where their competition with solid tides is likely to drive the body towards non-synchronized rotation states of equilibrium, as observed in the case of Venus. Contrary to other planetary layers, the atmosphere is sensitive to both gravitational and thermal forcings, through a complex dynamical coupling involving the effects of Coriolis acceleration and characteristics of the atmospheric structure. These key physics are usually not taken into account in modelings used to compute the evolution of planetary systems, where tides are described with parametrised prescriptions. In this work, we present a new ab initio modeling of atmospheric tides adapting the theory of the Earth’s atmospheric tides (Chapman & Lindzen 1970) to other terrestrial planets. We derive analytic expressions of the tidal torque, as a function of the tidal frequency and parameters characterizing the internal structure (e.g. the Brunt-Väisälä frequency, the radiative frequency, the pressure heigh scale). We show that stratification plays a key role, the tidal torque being strong in the case of convective atmospheres (i.e. with a neutral stratification) and weak in case of atmosphere convectively stable. In a second step, the model is used to determine the non-synchronized rotation states of equilibrium of Venus-like planets as functions of the physical parameters of the system. These results are detailed in Auclair-Desrotour et al. (2016a) and Auclair-Desrotour et al. (2016b).

Earth rotation deceleration/acceleration due to semidiurnal oceanic/atmospheric tides: Revisited with new calculation

The global oceanic/atmospheric tides exert decelerating/accelerating secular torques on the Earth rotation. We developed new formulations to accurately calculate amounts of two kinds of secular tidal torques. After Melchior, we found that an additional factor 1+k-l = 1.216, which has been formerly neglected, must be multiplied unto the tidal torque integral. By using our refined formulations and the recent oceanic/atmospheric global tide models, we found that: (i) semidiurnal oceanic lunar/solar tides exert decelerating torques of about −4.462×1016/−0.676×1016Nm respectively and (ii) atmospheric S2 tide exerts accelerating torque of 1.55×1015Nm. Former estimates of the atmospheric S2 tidal torque were twice as large as our estimate due to improper consideration of loading effect. We took the load Love number for atmospheric loading effect from Guo et al. (2004). For atmospheric loading of spherical harmonic degree two, the value of k'=−0.6031 is different from that for ocean loading as k'=−0.3052, while the latter is currently used for both cases – ocean/atmospheric loading – without distinction. We discuss (i) the amount of solid Earth tidal dissipation (which has been left most uncertain) and (ii) secular changes of the dynamical state of the Earth-Moon-Sun system. Our estimate of the solid Earth tidal torque is −4.94×1015Nm.

Density‐Temperature Synchrony in the Hydrostatic Thermosphere

AbstractThe paper presents a detailed analysis of the density‐temperature (ρ‐T) synchrony in the thermosphere using a hydrostatic general circulation model. The numerical models in general offer not only great potential for forecasting the transient response of the thermosphere but also are excellent tools for understanding the driving mechanisms of various thermospheric trends and features. This study investigates and isolates the dependency of the ρ‐T synchrony on the season, altitude, space weather, high‐latitude electrodynamics, and the lower atmospheric tidal spectrum. The results demonstrate that the previously reported ρ‐T synchrony begins around 300‐km (350‐km) altitude at the equator (high latitudes). The effect of the lower atmospheric tidal spectrum on the ρ‐T synchrony patterns seems to be only marginal and more noticeable during the equinox months. The study demonstrates that the ρ‐T phase lag is larger in the high latitudes of the summer hemisphere and evolves through the day and is attributable to ion drag and temperature fluctuations via soft particle precipitation. The study provides physical insights into how the winds contribute to the ρ‐T synchrony. In addition, the results show that geomagnetic activity contributes significantly to the ρ‐T synchrony; the underlying mechanism may be related to temperature enhancements in the high latitudes via Joule heating and associated nonlinear interactions. While the ρ‐T phase lags attributable to different solar activity levels are modest, the solar heating is the primary source that maintains the ρ‐T synchrony in the low/middle latitudes via upward propagating thermal tides.

Solar-locked and geographical atmospheric structures inferred from a Venus general circulation model with radiative transfer

Solar-locked and geographical atmospheric structures of daily averaged wind and temperature on Venus were investigated using an atmospheric general circulation model with Venusian topography and a two-stream radiative code and were compared with wind fields obtained from the Akatsuki ultraviolet imager. The horizontal wind fields simulated around the subsolar region are similar to the observed ones at the cloud top. Mid-latitude jets of ∼120 m s–1 and an equatorial fast flow of ∼90 m s–1 are formed around the cloud top. A poleward flow of >8 m s–1 is formed above the cloud layer, where solar heating is strong. Around the cloud top, a poleward flow of ∼1 m s–1 is confined within the equatorward flank of the jet core, whereas an indirect circulation is formed in the jet core by the eddy heat fluxes owing to the thermal tide and baroclinic waves. In solar-fixed coordinates, the subsolar-to-antisolar circulation is predominant around the cloud top. Thus, differences are significant between the zonal and dayside averages of the meridional wind and its related fluxes within the cloud layer. This suggests the zonal mean meridional wind of the Hadley circulation, eddy momentum, and heat fluxes from the one-side hemisphere must be estimated carefully. In the experiment including topography, a near-surface subrotation is formed in latitudinal zones over high land and mountains, a weakly stable layer is formed at 10–20 km at low latitudes, and the zonal wind is weakened at the cloud top over the Aphrodite Terra. Regional stationary modification of the atmospheric structure due to topographical waves appears in the cloud layer.

Type of Deterioration in Active Rollers for Hot Rolling Mill

The high prices of rolling mill cylinders, the energetic consumption and the lack of the alloying elements, determine the research development and studies regarding the improvement of the cylinder life service. The research presented within this paper aimed, at first, to describe the main rolling mill rollers failure types emphasizing the main destruction form – exfoliation of the external hard layer. The goal was to link the origin of this failure type to the Jacq thermal anomaly in heat transfer. This is a new approach on thermomechanical contact fatigue, taking into account the same location of the critical stresses for both mechanical load and thermal tide on the same contact surface. After the research was conducted on a lot of rolling mill rollers made by the same producer by cast iron with a hardened layer, one observed that the exfoliation, as a form of roll-specific damage, is due to the temperature difference between the layers. In poor or insufficient cooling conditions, which causes an adhesion phenomena in areas where the cohesion structure is affected in the superficial layer, a cleavage between the layers appears at a depth of installation of both the decisive mechanical stress and the Jacq thermal anomaly.

Author Correction: A changeable day in the life of Venus

In the version of this Sketch-Up originally published, labels describing atmospheric torques acting on Venus were incorrect. The sketch suggested that the speed-up effect of mountain waves is balanced by a slow-down from thermal tides; instead, both mountain waves and thermal tides speed up the rotation, and this effect is balanced by a slow-down from the solar gravitational torque on the solid body, which is transmitted to the atmosphere. This error has now been corrected in the online versions by adjusting the relevant labels; that is, “Mountain waves speed the planet up” has been changed to “Mountain waves and thermal tides speed the planet up”, and “Thermal tide slows the planet down” has been changed to “Solar gravitational torques slow the planet down”.

Variation of boundary‐layer wind spectra with height

This study revisits the height dependence of the wind speed power spectrum from the synoptic scale to the spectral gap. Measurements from cup and sonic anemometers at heights of 15 to 244 m are used. The measurements are from one land site, one coastal land‐based site and three offshore sites in the midlatitudes. There are two new findings. The first finding addresses the diurnal peak in the power spectrum. Our analysis suggests that there are two sources that contribute to the diurnal peak. One is related to surface‐driven processes and another is related to a pressure perturbation from the atmospheric tide. The second finding concerns the height dependence of the general spectrum. We describe the dependence through a so‐called effective roughness, which is calculated from wind spectra and represents the energy removal at different frequencies, and thus surface conditions in the footprint areas. The generalizable spectral properties of winds presented here may prove useful for validating numerical models.

Radiational tides: their double-counting in storm surge forecasts and contribution to the Highest Astronomical Tide

Abstract. Tide predictions based on tide-gauge observations are not just the astronomical tides; they also contain radiational tides – periodic sea-level changes due to atmospheric conditions and solar forcing. This poses a problem of double-counting for operational forecasts of total water level during storm surges. In some surge forecasting, a regional model is run in two modes: tide only, with astronomic forcing alone; and tide and surge, forced additionally by surface winds and pressure. The surge residual is defined to be the difference between these configurations and is added to the local harmonic predictions from gauges. Here we use the Global Tide and Surge Model (GTSM) based on Delft-FM to investigate this in the UK and elsewhere, quantifying the weather-related tides that may be double-counted in operational forecasts. We show that the global S2 atmospheric tide is captured by the tide-and-surge model and observe changes in other major constituents, including M2. The Lowest and Highest Astronomical Tide levels, used in navigation datums and design heights, are derived from tide predictions based on observations. We use our findings on radiational tides to quantify the extent to which these levels may contain weather-related components.