Atmospheric Tides Research Articles

Ultra‐Fast Kelvin Wave Packets in Mars' Atmosphere and Their Interactions With Tides as Viewed by MAVEN/NGIMS and MRO/MCS

AbstractA key element of successful aerobraking operations at Mars is accurate thermospheric density predictions. Evidence suggests that much of the longitude variability in Mars' aerobraking region is associated with atmospheric tides, and the day‐to‐day variability is connected with tidal modulation by longer‐period global‐scale waves. Specifically, ultra‐fast Kelvin waves (UFKWs) and their modulation of the tidal spectrum play a key role in coupling Mars' lower (<∼80 km) and middle (∼80–100 km) atmosphere with the aerobraking region above. In this study, over 5 years of Mars Atmosphere and Volatile Evolution Neutral Gas and Ion Mass Spectrometer CO2 density observations are employed to reveal prominent, frequent, and persistent 2.5‐ to 4.5‐day UFKW packets in the whole Martian middle and upper thermosphere (ca. 150–200 km), and large secondary waves arising from their nonlinear interactions with the tidal spectrum. Detailed analyses focusing on a prominent ∼2.5‐day UFKW event in late 2015 demonstrate primary and secondary wave amplitudes growing twofold with altitude from ∼7%–14% near 150 km to ∼12%–25% near 200 km and their combined effects to account for ∼60%–80% of the altitude‐longitudinal variability of Mars' thermospheric density. Concurrent temperature measurements from Mars Reconnaissance Orbiter Mars Climate Sounder reveal consistent wave signatures near 80 km altitude suggesting propagation of both primary and secondary waves from the lower atmosphere. This study demonstrates that UFKWs and secondary waves from UFKW‐tide interactions are sources of significant altitude‐longitude variability in the Mars' aerobraking region that should be accounted for when analyzing satellite observations and nonlinear models.

Climatology of atmospheric solar tidal mode effects on ionospheric F2 parameters over the American sector during solar minimum between cycles #23 and #24

This work presents the contribution of solar atmospheric tides (diurnal, semidiurnal, and terdiurnal modes) to the variability of the parameters critical frequency (foF2) and peak height of the F2-layer (hmF2) in the American sector during the transition of solar cycles #23 and #24, a period considered one of the lowest solar activities of the modern era. The Digisonde data available in the GIRO data center were analyzed (12 stations), and the solar tide modes were evaluated regarding their amplitude, latitude, and seasonal dependence. The results showed that the hmF2 and foF2 strongly depend on latitude and seasonality, being more intense in the stations located in the south hemisphere. The same behavior is seen for the tidal amplitude fitted in these parameters, except for hmF2 diurnal tide, which is more intense at latitudes farther from the equator. Moreover, the seasonal variability of the amplitude of hmF2 in most cases presented an annual and semiannual component. A terannual component was also observed in 8 h tide mode in the height and frequency parameters. Likewise, what was observed in foF2, the variability in the mean amplitude and different modes of tides of hmF2 are higher over the sectors located in the southern hemisphere.

Rotational/divergent flow and energy conversion of thermal tides in a Venus general circulation model

Venusian thermal tides are discussed as a three-dimensional response to solar heating, which is strongly modified by both barotropic and baroclinic energy conversions in a fully developed super-rotation. Thermal tides such as gravity waves propagate upward and downward from the cloud top (∼65 km) at low latitudes, while tidal gyres such as Rossby waves appear at high latitudes according to the general circulation model (GCM) developed at Atmosphere and Ocean Research Institute (AORI), The University of Tokyo. Around the cloud-top heating maximum, strong poleward/equatorward tidal flows are formed by both divergent and rotational flows that are in phase, and equatorial super-rotation is accelerated by the equatorward and vertical momentum fluxes of the diurnal tides and the vertical flux of the semidiurnal tides. These thermal tides are a result of solar heating as well as energy conversions from the zonal-mean jet and its related temperature gradient. The gravity wave is thermally forced in the cloud-top heating maximum where diabatic heating produces eddy available potential energy. The Rossby waves are formed in mid- and high-latitudinal regions where diurnal barotropic energy conversion occurs around the zonal-mean jet core and semidiurnal baroclinic energy conversion occurs below the cloud layer far from the solar heating region.

Spin and orbital dynamics of planets undergoing thermal atmospheric tides using a vectorial approach

Earth-mass planets are expected to have atmospheres and experience thermal tides raised by the host star. These tides transfer energy to the planet that can counter the dissipation from bodily tides. Indeed, even a relatively thin atmosphere can drive the rotation of these planets away from the synchronous state. Here we revisit the dynamical evolution of planets undergoing thermal atmospheric tides. We use a novel approach based on a vectorial formalism, which is frame independent and valid for any configuration of the system, including any eccentricity and obliquity values. We provide the secular equations of motion after averaging over the mean anomaly and the argument of the pericenter, which are suitable to model the long-term spin and orbital evolution of the planet.

Martian Equatorial Atmospheric Tides From Surface Observations

AbstractDiurnal solar radiation causes global oscillations in pressure, temperature, and wind fields, known as atmospheric tides, which are further modified by topography, surface properties, and atmospheric dust loading. Hence, the tides are a combination of sun‐synchronous and non sun‐synchronous tides that propagate around the planet both eastward and westward. In the Martian tropics, atmospheric tides dominate daily pressure variations on the surface. Therefore, surface observing platforms are extremely useful for detailed analysis of atmospheric tides. In this investigation, we analyze diurnal and semi‐diurnal components of atmospheric surface pressure measured by the simultaneously operating InSight and Mars Science Laboratory (MSL) payloads. We utilize observations of the time period from Martian year (MY) 34 solar longitude 296° to MY 36 solar longitude 53°. The diurnal tide average amplitude is 17 Pa with an average phase of 03:39 local true solar time (LTST), while the semi‐diurnal tide average amplitude and phase are 7 Pa and 09:34 LTST for the InSight. The corresponding values for the MSL are 33 Pa with 04:25 LTST for the diurnal and 10 Pa with 09:36 LTST for the semi‐diurnal component. Thermo‐topographic lateral hydrostatic adjustment flow generated by topography causes the higher diurnal amplitude observed by MSL. Both platforms observe a similar response between these harmonic components and dust loading. Furthermore, amplitudes obtained from a Mars Climate Database mimic the observations well. Our study provides for the first time a comparison of atmospheric tides at two simultaneously observing tropical surface platforms for more than 1 MY.

Evidence of oceanic and atmospheric tides in underwater ambient noise time records

Multiyear time records of low-frequency ocean ambient noise show clear evidence of a modulating influence by major semi-diurnal and diurnal gravitational tides. These are displayed by means of a variance spectral analysis of noise time records obtained from the United Nations Comprehensive Nuclear Test Ban Treaty Organization for hydrophone stations at Wake Island, Ascension Island and Diego Garcia. Narrow-band noise frequencies ranged from ½ to 10 Hz. There is also evidence in the noise records of a diurnal atmospheric tide related to solar radiation and atmospheric loading. This same tidal presence is seen in wind speed records as well. Part of the challenge in the analysis is to distinguish between expected diurnal behavior in wind speed, with its accompanying effect on ambient noise, and the presence of actual tidal lines. A brief history of earlier observations of diurnal variation in underwater acoustics is presented, along with some suggestions of causal mechanisms.

Atmospheric Tides at Low Latitudes in the Martian Upper Atmosphere Observed by MAVEN IUVS

AbstractThe present work studies the variation of the wave 3 structure in the Martian upper atmosphere at low latitudes. CO2 densities produced by the Imaging Ultraviolet Spectrograph (IUVS) onboard the Mars Atmosphere and Volatile EvolutioN spacecraft from October 2014 to September 2021 are utilized to study the variation of the wave 3 structure under different seasons. By normalizing the densities to a fixed Extreme Ultraviolet level and applying harmonic fitting techniques, the wave 3 structures are derived from the IUVS observations. We find that the wave 3 structure tends to propagate eastward with increasing local time and altitude at low latitudes, which is consistent with the variability of the wave 3 structure at high latitudes. The altitudinal variation of the wave 3 structure also indicates that the dissipation effects become essential in the Martian upper atmosphere. By comparing the shifting speed of the wave structure with the phase speed of prominent tides in different seasons, we find that DE2 and SE1 jointly generate the wave 3 structure at low latitudes. This is confirmed by the seasonal variations of DE2 and SE1 proposed by Mars Climate Database (MCD) latitude‐Ls predictions. Comparisons of the MCD predictions with the height‐latitude amplitude distributions of the wave 3 structure reveal the existence of both DE2 and SE1 tides. By decomposing the wave 3 structure into latitudinal symmetric and antisymmetric components and comparing it with the first few Hough modes of DE2 and SE1, we confirm that DE2 and SE1 are the possible candidates that generate the wave 3 structure.

Diurnal Cycle of Tropospheric Winds over West Sumatra and Its Variability Associated with Various Climate and Weather Modes

The typical diurnal variability of tropospheric winds over West Sumatra and their changes associated with El Niño Southern Oscillation, Quasi-Biennial Oscillation, Madden–Julian Oscillations and convectively coupled Kelvin waves during the extended boreal winter season are investigated based on nineteen years of observations from Equatorial Atmosphere Radar in Kototabang, Indonesia. Sub-diurnal wind variability is assessed based on the amplitude and phase of the diurnal (24 h) and semidiurnal (12 h) modes.The results show that composite diurnal variability is dominated by cloud-induced circulation and thermal tides. Although these sub-diurnal modes do not change the daily mean wind direction, they modulate velocities throughout the day. Typical diurnal evolution of the vertical wind component is consistent with changes in the latent heating profiles associated with the evolution of a cloud field from cumulus before noon to deep convection in the afternoon and stratiform clouds in the evening. El Niño Southern Oscillation and Quasi-Biennial Oscillation affect the mean tropospheric winds, throughout the troposphere and above 250 hPa, respectively, but do not affect sub-diurnal amplitudes. Eastward propagating Madden–Julian Oscillations and convectively coupled Kelvin waves impact both the mean and sub-diurnal tropospheric wind variability. Both horizontal and vertical winds show the largest variability in the lower and mid troposphere (below 400 hPa). The observed variability in the vertical wind component highlights that large-scale phenomena interact with both the local evolution and progression of a cloud field through dynamical feedback.

Technical note: Novel analytical solution for groundwater response to atmospheric tides

Abstract. Subsurface hydraulic and geomechanical properties can be estimated from well water level responses to Earth and atmospheric tides. However, the limited availability of analytical solutions restricts the applicability of this approach to realistic field conditions. We present a new and rigorous analytical solution for modeling flow between a subsurface–well system caused by harmonic atmospheric loading. We integrate this into a comprehensive workflow that also estimates subsurface properties using a well-established Earth tide method. When applied to groundwater monitoring datasets obtained from two boreholes screened in a sand aquifer in the Mary–Wildman river region (Northern Territory, Australia), estimated hydraulic conductivity and specific storage agree. Results also indicate that small vertical leakage occurs in the vicinity of both boreholes. Furthermore, the estimated geomechanical properties were within the values reported in the literature for similar lithological settings. Our new solution extends the capabilities of existing approaches, and our results demonstrate that analyzing the groundwater response to natural tidal forces is a low-cost and readily available solution for unconsolidated, hydraulically confined, and undrained subsurface conditions. This approach can support well-established characterization methods, increasing the amount of subsurface information.

The response of borehole water levels in an ophiolitic, peridotite aquifer to atmospheric, solid Earth, and ocean tides

Peridotite aquifers are ubiquitous on Earth, but most are in the deep-sea, and thus difficult to access. Ophiolites provide a unique opportunity to study peridotite aquifers, and the Oman Drilling Project established a Multi-Borehole Observatory in a peridotite terrain of the Samail ophiolite. We use the water level response of two 400-m deep boreholes (BA1B, BA1D) to solid Earth, ocean, and atmospheric tides to investigate the hydromechanical structure of the aquifer. The two boreholes are offset by ∼ 100 m but exhibit markedly different tidal responses, indicating a high degree of short-length-scale heterogeneity. Hole BA1B does not respond to tidal strain or barometric loading, consistent with the behavior of an unconfined aquifer. Hole BA1D responds to both tidal strain and barometric loading, indicating some degree of confinement. The response to applied strain, which includes a non-negligible ocean tidal loading component, is consistent with a partially confined, low conductivity aquifer. The response to barometric loading appears to be affected by the complex hydrological structure of the surficial zone and we were not able to fit the observations to within error. Aquifer conductivity estimates for Hole BA1D based on the response to tidal strain are within a factor of ∼ 3 of pumping test estimates.

Dynamics of Mid‐Latitude Sporadic‐E and Its Impact on HF Propagation in the North American Sector

AbstractSporadic‐E (Es) are thin layers of enhanced ionization observed in the E‐region, typically between 95 and 120 km altitude. Es plays an important role in controlling the dynamics of the upper atmosphere and it is necessary to understand the geophysical factors influencing Es from both the scientific and operational perspectives. While the wind‐shear theory is widely accepted as an important mechanism responsible for the generation of Es, there are still gaps in the current state of our knowledge. For example, we are yet to determine precisely how changes in the dynamics of horizontal winds impact the formation, altitude, and destruction of Es layers. In this study, we report results from a coordinated experimental campaign between the Millstone Hill Incoherent Scatter Radar, the SuperDARN radar at Blackstone, and the Millstone Hill Digisonde to monitor the dynamics of mid‐latitude Es layers. We report observations during a 15‐hr window between 13 UT on 3 June 2022 and 4 UT on 4 June 2022, which was marked by the presence of a strong Es layer. We find that the height of the Es layer is collocated with strong vertical shears in atmospheric tides and that the zonal wind shears play a more important role than meridional wind shears in generating Es, especially at lower altitudes. Finally, we show that in the presence of Es, SuperDARN ground backscatter moves to closer ranges, and the height and critical frequency of the Es layer have a significant impact on the location and intensity of HF ground scatter.

Thermal Tides on Mars Before and During the 2018 Global Dust Event as Observed by TIRVIM‐ACS Onboard ExoMars Trace Gas Orbiter

AbstractMigrating tides dominate the tropical climate on Mars and are known to reach high amplitudes during global dust events (GDE). In this study, we characterize the amplitude, phase and vertical wavelength of the diurnal and semidiurnal migrating tides in Mars' lower atmosphere (up to 50 km) by exploiting temperature vertical profiles retrieved from TIRVIM, an infrared spectrometer onboard the ExoMars Trace Gas Orbiter covering multiple local times. Observations from the Mars Climate Sounder onboard the Mars Reconnaissance Orbiter are used to complement the local time coverage when needed, and to estimate a seasonal trend to subtract from TIRVIM observations. We focus on two time periods in Martian Year 34, near Ls = 150° and near Ls = 200° (during the 2018 GDE). The characteristics of the migrating tides at Ls = 150° agree very well with tidal theory: a downward propagation, amplitudes of typically 2–5 K, and a larger vertical wavelength for the semidiurnal compared to the diurnal mode. Comparisons with model predictions from the Mars Planetary Climate Model reveal an excellent agreement, except for a slightly different phase of the diurnal tide. During the GDE, the tide pattern changes spectacularly: the diurnal tide amplitude reaches 35 K at 65°S and 17 K at 50°N, being vertically trapped up to 10 Pa. The semidiurnal tide is maximum near 20–30°S with an amplitude of 8–12 K. The phase of this mode is tilted with latitude, which was not the case before the storm. This indicates a significant contribution of the asymmetric Hough modes due to hemispheric asymmetry in the dust distribution.

Variability and distribution of nighttime equatorial to mid latitude ionospheric irregularities and vertical plasma drift observed by FORMOSAT-5 Advanced Ionospheric Probe in-situ measurements from 2017 – 2020

Irregularities in ionospheric plasma distribution can result in severe scintillation and disruption to the radio frequencies utilized for satellite communications and navigation. In the low and mid latitudes, these irregularities can include Equatorial Plasma Bubbles (EPBs) and Travelling Ionospheric Disturbances (TIDs). EPBs are irregularities manifesting in low latitude nighttime ionosphere plasma density that can extend along magnetic field lines with zonal scales on the order of 100 km or less, while TIDs are propagating wave disturbances. High frequency in-situ measurements of ionospheric plasma aboard spacecraft in Low Earth Orbit (LEO) are a direct measurement of irregularities in plasma density and are therefore valuable for resolving EPB and TID occurrences, variability, and relation to other ionospheric parameters that are believed to play a driving role in the formation of such irregularities. In this study, we utilize observations taken over a three-year period between 2017 and 2020 by the Advanced Ionospheric Probe (AIP) carried aboard the FORMOSAT-5 satellite to examine the spatial, seasonal, and interannual variability of equatorial to mid latitude ionospheric irregularities and vertical ion drift during this time. AIP provides in-situ measurements of ion density and vertical ion drift in the equatorial to mid latitude ionosphere at approximately 720 km altitude with local times between 22:00 – 23:00 local time. Our global scale results resolve distinct and inter-annually recurrent seasonal patterns in the distribution of nighttime ionospheric irregularities and vertical plasma drift during this time. Elevated occurrences of ion density irregularities are resolved along the Equatorial Ionization Anomaly (EIA) latitudes, while notable occurrences with variability consistent with EPBs also observed along the low and equatorial magnetic latitudes. Zonal variability of equatorial irregularities consistent with the signatures of nonmigrating atmospheric tides are observed. It is also notable that the occurrences and geographic distribution of ion density irregularities showed a considerable level of interannual variability, especially at mid latitudes over the South Atlantic and Southern African sectors, which showed much higher levels of irregularities in 2017–––2018, compared to 2019 and 2020. In comparison, the spatial and interannual variation of the co-located vertical ion drifts were much more consistent during the years examined, indicating that the driver for the observed interannual variability in ion density irregularities cannot be attributed to the vertical ion drift at the same time and location of the observations. This highlights the need for in-situ instruments distributed across multiple satellites in different local time zones.

Why the day is 24 hours long: The history of Earth's atmospheric thermal tide, composition, and mean temperature.

The Sun drives a semidiurnal (12-hour) thermal tide in Earth's atmosphere. Zahnle and Walker suggested that an atmospheric oscillation with period Pres ≈ 10.5 hours resonated with the Solar driving ≈600 million years ago (Ma), when the length of day (lod) was ≈21 hours. They argued that the enhanced torque balanced the Lunar tidal torque, fixing the lod. We explore this hypothesis using two different global circulation models (GCMs), finding Pres = 11.4 and 11.5 hours today, in excellent agreement with a recent measurement. We quantify the relation between Pres, mean surface temperature [Formula: see text], composition, and Solar luminosity. We use geologic data, a dynamical model, and a Monte Carlo sampler to find possible histories for the Earth-Moon system. In the most likely model, the lod was fixed at ≈19.5 hours between 2200 and 600 Ma ago, with sustained high [Formula: see text] and an increase in the angular momentum LEM of the Earth-Moon system of ≈5%.

Microwave radiometer observations of the ozone diurnal cycle and its short-term variability over Switzerland

Abstract. In Switzerland, two ground-based ozone microwave radiometers are operated in the vicinity of each other (ca. 40 km): the GROund-based Millimeter-wave Ozone Spectrometer (GROMOS) in Bern (Institute of Applied Physics) and the Stratospheric Ozone MOnitoring RAdiometer (SOMORA) in Payerne (MeteoSwiss). Recently, their calibration and retrieval algorithms have been fully harmonized, and updated time series are now available since 2009. Using these harmonized ozone time series, we investigate and cross-validate the strato–mesospheric ozone diurnal cycle derived from the two instruments and compare it with various model-based datasets: the dedicated GEOS-GMI Diurnal Ozone Climatology (GDOC) based on the Goddard Earth Observing System (GEOS-5) general circulation model, the Belgian Assimilation System for Chemical ObsErvations (BASCOE) – a chemical transport model driven by ERA5 dynamics, and a set of free-running simulations from the Whole Atmosphere Community Climate Model (WACCM). Overall, the two instruments show very similar ozone diurnal cycles at all seasons and pressure levels, and the models compare well with each other. There is a good agreement between the models and the measurements at most seasons and pressure levels, and the largest discrepancies can be explained by the limited vertical resolution of the microwave radiometers. However, as in a similar study over Mauna Loa, some discrepancies remain near the stratopause, at the transition region between ozone daytime accumulation and depletion. We report similar delays in the onset of the modelled ozone diurnal depletion in the lower mesosphere. Using the newly harmonized time series of GROMOS and SOMORA radiometers, we present the first observations of short-term (sub-monthly) ozone diurnal cycle variability at mid-latitudes. The short-term variability is observed in the upper stratosphere during wintertime, when the mean monthly cycle has a small amplitude and when the dynamics are more important. This is shown in the form of strong enhancements of the diurnal cycle, reaching up to 4–5 times the amplitude of the mean monthly cycle. We show that BASCOE is able to capture some of these events, and we present a case study of one such event following the minor sudden stratospheric warming of January 2015. Our analysis of this event supports the conclusions of a previous modelling study, attributing regional variability of the ozone diurnal cycle to regional anomalies in nitrogen oxide (NOx) concentrations. However, we also find periods with an enhanced diurnal cycle that do not show much change in NOx and where other processes might be dominant (e.g. atmospheric tides). Given its importance, we believe that the short-term variability of the ozone diurnal cycle should be further investigated over the globe, for instance using the BASCOE model.

Observed Dawn and Twilight Pressure Sudden Peaks in the Global Martian Surface and Possible Relationships With Atmospheric Tides

AbstractMultilanders and rovers on Mars have observed the diurnal variation in surface pressure with two significant peaks at dawn and twilight (around 8:00 a.m. and 8:00 p.m.) at different locations near the equinox. The Dynamic Meteorology Laboratory Martian General Circulation Model (GCM) simulates similar phase‐locked surface pressure fluctuations. The surface pressure peaks at a certain local time occur at most mid‐ and low‐latitude locations, as GCM simulations suggested. By reconstructing the surface pressure variation from the horizontal mass flux obtained in the GCM simulations, we find that the pressure fluctuations are due to the diurnal variation in the horizontal wind divergence and convergence in the Martian tropical troposphere. The diurnal variation in surface pressure corresponds to the migrating diurnal tidal wind, with the enhanced convergence due to the overlap of the 4‐hr and 6‐hr tides before 8:00 a.m. and 8:00 p.m. Although the amplitudes of the 4‐hr and 6‐hr tides are smaller than those of diurnal tides, the convergences/divergences caused by the 4‐hr/6‐hr tidal winds at different altitudes are in phase and added up together to create a mass flux comparable to that induced by diurnal/semidiurnal components and lead to rapid pressure fluctuations. The 4‐hr/6‐hr tidal amplitudes and the two pressure peaks at dawn and twilight are the strongest near the equinox.

A Surface to Exosphere Non‐Orographic Gravity Wave Parameterization for the Mars Planetary Climate Model

AbstractIn this paper, the non‐orographic gravity waves (GW) parameterization of the Mars Planetary Climate Model (PCM) previously implemented by Gilli et al. (2020, https://doi.org/10.1029/2018JE005873) is revisited and extended to the exobase (∼250 km). The simulations performed with the new scheme correct some known biases in the modeled thermal tide amplitudes and polar warming, improving the agreement with Mars Climate Sounder (MCS) observed thermal structures and tides below ∼100 km. Additionally, we find that the simulated densities above 150 km are compatible with NGIMS (Neutral Gas and Ion Mass Spectrometer) measured abundances. Large drag depositions ranging up to >∼950 m s−1 sol−1 are induced at altitude of 90–170 km due to the wave saturation (breaking) and depletion, leading to winds damped to magnitudes of ∼150–225 and ∼80 m s−1 in the zonal and meridional directions, respectively. Resulting temperature variations are ∼±10–30 K or 5%–10% at most latitudes except in the polar regions (where they can reach ∼±30–60 K). The results indicate that non‐orographic GW play a significant role in the dynamics of the middle‐upper atmosphere of Mars via the induced transfer of momentum and energy from the lower atmosphere.

Atmospheric tides over Brazil

The mean annual components of the solar and lunar atmospheric tides over Brazil were obtained from the analysis of surface pressure data from 369 modern weather stations. The spatial coverage area and density of the data presented provide a high level of detail that has not been presented before. For the solar atmospheric tide, it was found that the amplitudes of the diurnal and semidiurnal components are comparable, each ranging from 0.2–1.7 mbar. The diurnal amplitude is irregularly distributed and influenced by the contour of the continent, its terrain, and climate. In contrast, the semidiurnal amplitude is more regularly distributed, measuring about 1.4 mbar at the Equator and decreasing towards higher latitudes. The amplitude of the lunar tide is normally distributed over the country, with a mean value of 0.08 mbar. The parameters obtained are spatially coherent, present little noise, and are both comprehensive and accurate. In addition, some statistical guidance on how to detect atmospheric tides properly at different latitudes is provided.

Short-Period Variation of the Activity of Atmospheric Turbulence in the MLT Region over Langfang

In this paper, we investigate the activity of atmospheric turbulence in the MLT region and the relationship between the activity of atmospheric turbulence and atmospheric wave activity. We use data from the Langfang MF radar (39.4∘N, 116.7∘E) from July 2019 to June 2020 and NRLMSIS 2.0 to calculate the parameters of atmospheric wave activity and atmospheric turbulence energy dissipation rate (ε). Atmospheric ε is modulated by different periods at different altitudes, and while there are 12 h and 24 h periods at all altitudes, the main period is different at different altitudes. A comparison of the ε with atmospheric tide activity shows that tides have an effect on ε, and the influence of tides on ε may be different at different altitudes. The pattern of variation in ε is similar to that of the atmospheric activity of the gravity wave, with both ε and the atmospheric activity of the gravity wave showing significant semi-annual variation.

Mid-Proterozoic day length stalled by tidal resonance

We present statistical analysis of a compilation of observational constraints on the Precambrian length of day and find that the day length stalled at about 19 h for about 1 billion years during the mid-Proterozoic. We suggest that the accelerative torque of atmospheric thermal tides from solar energy balanced the decelerative torque of lunar oceanic tides, temporarily stabilizing Earth’s rotation. This stalling coincides with a period of relatively limited biological evolution known as the boring billion.