Internal Atmospheric Gravity Waves Research Articles

On geomagnetic and ionospheric variations after the strong eruption of Shiveluch volcano 2023

Ground-based magnetometers and vertical ionospheric sounding stations were used to record specific variations in the geomagnetic field caused by disturbances in the current systems of the lower ionosphere and the electron density of the upper ionosphere after a strong volcanic eruption in Kamchatka (Russia) on April 10, 2023. Analysis of the measurement results of two series of explosions showed that the impact on the lower ionosphere is carried out through both seismic Rayleigh waves (which are a source of acoustic waves propagating into the ionosphere), and atmospheric internal gravity waves generated by explosions. At distances from the source of up to a thousand kilometers, a repeatability of the pattern of ionospheric disturbances was discovered after each of the six volcanic explosions. At larger distances in the ionosphere, signals from acoustic waves caused by Rayleigh waves are clearly recorded, and isolating signals from atmospheric internal waves is difficult due to the influence of disturbances from other external sources.

Wave Perturbations of the Lower and Upper Ionosphere during the 2019 Faxai Tropical Typhoon

In this paper, we studied the response of the lower and upper ionosphere to the passage of TyphoonFaxai 2019 using the regional network of ultralong-wave radio translucence stations in the Far East region ofRussia and measurements of electron density perturbations using the SWARM mission satellites. The presentedexperimental data clearly demonstrate wave perturbations of the amplitude and phase of the ULW signal,as well as the electron density during the active stage of the typhoon. The parameters of wave perturbationscorrespond to atmospheric internal gravity waves. The maximum spectral density of wave perturbations in thelower ionosphere corresponds to 16–20 min. A mechanism for the impact of internal waves on the ionosphere,which is due to polarization fields arising from the wave motion of plasma in the lower part of the F-region, isproposed. These fields projected along the geomagnetic field lines make it possible to interpret the observedvariations in the phase of the ULW signal and variations in the electron density in the upper ionosphere

Destructive Potential of Planetary Meteotsunami Waves beyond the Hunga Tonga–Hunga Ha‘apai Volcano Eruption

Abstract Worldwide tsunamis driven by atmospheric waves—or planetary meteotsunami waves—are extremely rare events. They mostly occur during supervolcano explosions or asteroid impacts capable to generate atmospheric acoustic-gravity waves including the Lamb waves that can circle the globe multiple times. Recently, such ocean waves have been globally recorded after the Hunga Tonga–Hunga Ha‘apai volcano eruption on 15 January 2022, but did not pose any serious danger to the coastal communities. However, this study highlights that the mostly ignored destructive potential of planetary meteotsunami waves can be compared to the well-studied tsunami hazards. In practice, several process-oriented numerical experiments are designed to force a global ocean model with the realistic atmospheric response to the Hunga Tonga–Hunga Ha‘apai event rescaled in speed and amplitude. These simulations demonstrate that the meteotsunami surges can be higher than 1 m (and up to 10 m) along more than 7% of the world coastlines. Planetary meteotsunami waves thus have the potential to cause serious coastal damages and even human casualties during volcanic explosions or asteroid impacts either releasing intense acoustic energy or producing internal atmospheric gravity waves triggering the deep-ocean Proudman resonance at a speed of ∼212 m s−1. Based on records of catastrophic events in Earth’s history, both scenarios are found to be realistic, and consequently, the global meteotsunami hazards should now be properly assessed to prepare for the next big volcanic eruption or asteroid impact even occurring inland.

Отклик ионосферы на прохождение тайфунов по наблюдениям методом СДВ-радиопросвечивания

The response of the lower ionosphere to the passage of several dozen typhoons has been studied using a regional network of VLF stations in the Russian Far East. The experimental data presented in all cases clearly demonstrates wavelike disturbances of the subionospheric VLF signal amplitude and phase during the active stage of typhoons crossing radio paths. With the exception of magnetoactive and seismoactive days, this means that the disturbances generated by a typhoon, when propagating into the upper ionosphere, pass through the lower ionosphere, causing corresponding disturbances in the amplitude and phase of the VLF signal. Spectral analysis shows that the range of the wave disturbances detected corresponds to the periods of atmospheric internal gravity waves (IGW). A mechanism of the action of IGWs on the lower ionosphere is proposed which allows us to interpret the VLF signal phase variations observed. According to this mechanism, the action of IGW on the lower ionosphere is caused by polarization fields arising during the wave motion of plasma in the lower part of the F layer. These fields projected along geomagnetic field lines into the lower ionosphere cause the upper wall of the Earth—ionosphere waveguide to rise or fall.

Ionospheric response to the passage of typhoons observed by subionospheric VLF radio signals

The response of the lower ionosphere to the passage of several dozen typhoons has been studied using a regional network of VLF stations in the Russian Far East. The experimental data presented in all cases clearly demonstrates wavelike disturbances of the subionospheric VLF signal amplitude and phase during the active stage of typhoons crossing radio paths. With the exception of magnetoactive and seismoactive days, this means that the disturbances generated by a typhoon, when propagating into the upper ionosphere, pass through the lower ionosphere, causing corresponding disturbances in the amplitude and phase of the VLF signal. Spectral analysis shows that the range of the wave disturbances detected corresponds to the periods of atmospheric internal gravity waves (IGW). A mechanism of the action of IGWs on the lower ionosphere is proposed which allows us to interpret the VLF signal phase variations observed. According to this mechanism, the action of IGW on the lower ionosphere is caused by polarization fields arising during the wave motion of plasma in the lower part of the F layer. These fields projected along geomagnetic field lines into the lower ionosphere cause the upper wall of the Earth—ionosphere waveguide to rise or fall.

The lower ionosphere disturbances observed during the chain of the meteotsunamis in the Mediterranean Sea in June 2014

In June 2014, a number of meteotsunamis were detected in the Mediterranean and Black Sea area. These meteotsunamis were initiated by a unique high-altitude dynamical system which was initially originated above Spain and traveled across the Mediterranean Sea towards Black Sea and Turkey. Meteotsunamis unlike tsunamis driven by strong earthquakes are local events, and their formation has different mechanism. Atmospheric internal gravity waves (IGWs) are one of the main known sources of meteotsunamis (e.g. Vilibic et al. in Pure Appl Geophys 165:2169–2195, 2008). The synoptic system produced short-lived and small-scale atmospheric pressure perturbations which drifted with the jet stream-like bubbles and generated tsunami-like waves in the open waters. The bubbles with typical dimensions 15–60 km continuously form and collapse in the atmosphere at altitudes of 3–6 km. Such a “boiled” atmosphere generated IGWs propagating both downward, where they produced meteotsunamis (presumably under Proudman resonance condition) and upward into the ionosphere, with following dissipation and excitation of plasma density perturbations. One of the few experimental techniques, which can monitor perturbations of the ionization within the lower ionosphere, uses long-wave probing by very low and low frequency (VLF/LF) radio signals. To study the ionospheric disturbances observed during the chain of meteotsunamis affecting the Mediterranean Sea, we used VLF/LF data collected in South Europe by “The International Network for Frontier Research on Earthquake Precursors”. By applying the spectral analysis method to the anomalous VLF/LF signals, it was found that revealed periods of the signal variations were from 10 to 40–70 min in different stations, which are in the range of the atmospheric pressure oscillations and the meteotsunami events. These periods also correspond to the periods of IGWs.

The Balearic rissaga: from pioneering research to present-day knowledge

The pioneering work done in late 1970s and early 1980s on research into rissaga events or meteotsunamis in the Balearic Islands is briefly reviewed in this paper and contrasted with the present state of the art on the phenomenon. The early research phase used existing observational evidence to construct a doctrine for the initial comprehension and forecasting of the phenomenon. By the beginning of the 1980s, it had already been established that the rissaga is a marine response to quick atmospheric pressure oscillations in resonance conditions, initially attributed exclusively to internal atmospheric gravity waves and later to convective pressure jumps too. Forty years later, new observational methods have provided a much richer database, with theoretical research and the use of forecasts using numerical models underpinning a much more solid perspective. With regard to predictability, quick atmospheric pressure oscillations were associated with a three-layer atmospheric vertical structure from the beginning: a thermodynamically neutral lower layer of Mediterranean air, a thermal inversion layer (Saharan air lying above and Mediterranean air below) and a deep upper layer with conditional instability in at least some strata. This structure is compatible with a high-level trough or cut-off low over the Iberian Peninsula; strong south-westerly flow over the Western Mediterranean area; jet stream speed being reached at the highest tropospheric levels, and forced Saharan air advection at the low/medium levels. A weak low-pressure area is usually present at low levels in the Mediterranean. The identification of the meteorological framework favourable to a rissaga event soon led to a probabilistic and purely meteorological forecasting method for the rissaga phenomenon. This method is still used today, albeit in combination with objective methods, some of which are based on the use of coupled atmospheric and oceanic forecasting models.

Orbital Maintenance of a Constellation of CubeSats for Internal Gravity Wave Tomography

The advent of radio occultation (RO) instruments aboard CubeSats leads to the possibility of a mission to sound atmospheric internal gravity waves if such satellites are deployed in close-flying constellation. The satellites in the constellation must have slightly perturbed orbital inclinations in order to spread the RO soundings within clusters in two horizontal dimensions, and consequently the satellites will disperse because they will experience different rates of regression of nodes. This dispersion must be countered by propulsive maneuvering in order to maintain the close formation of the constellation. Here, a theoretical approach to the necessary propulsive maneuvering is presented and simulations using comprehensive orbit propagators are performed to analyze four propulsive systems: two cold gas propulsion systems and two electrospray propulsion systems. Cold gas propulsion permits greater separations in inclination between satellites in a constellation by virtue of the greater thrust they can exert on a spacecraft: cold gas propulsion can permit inclination separations of 1 to 10 $^\circ$ while electrospray limits separations to less than 0.2 $^\circ$ . On the other hand, electrospray propulsion provides much longer mission lifetime by virtue of the greater total thrust it offers: cold gas propulsion expends all of its fuel in maintaining the constellation formation in less than approximately 100 days while electrospray propulsion can maintain formation for greater than 1000 days before expending all of its fuel. Mission lifetime is the most critical consideration for a mission, thus electrospray propulsion is recommended for the constellation-flying of CubeSats, but the accelerations that they offer must be greatly increased to enable spacecraft separations useful for tomography of internal gravity waves. Note that any close-flying constellation involving satellites with slightly perturbed inclinations will experience the same dispersing effect as the constellations described herein and, thus, require the same propulsive maneuvering to maintain formation.

Seasonal Variations and Global Wave Distributions in the Mars Thermosphere From MAVEN and Multisatellites Accelerometer‐Derived Mass Densities

AbstractMartian lower thermospheric variations are complex due to internal surface dust storms and external solar activities. However, limited Martian measurement data are restricted to observe and understand its variations in the past. In this paper, multisatellite accelerometer‐derived densities and the Mars Climate Database are used to investigate seasonal variations, gravity waves, and coupling effects with the internal and external inputs, including Mars Global Surveyor, Mars Reconnaissance Orbiter, Mars Odyssey, and Mars Atmosphere and Volatile EvolutioN Mission. The diurnal and seasonal structures are reconstructed by the data, and the phase of the cycles is formed by solar heating/ionizing processes. Both amplitude and phase are impacted by surface dust activities during autumn and winter, for which density increases about 1.5–3.5 times compared to spring and summer seasons. A parameterized model that includes a newly introduced dust index is proposed to well fit and reinterpret the seasonal cycles. Furthermore, the coupling process between internal atmospheric gravity waves (IAGWs) and dust activities are investigated and explained. During dust storm times/seasons, the IAGWs exhibit both narrower amplitude peaks and deposit their energy at higher altitudes relative to “clear sky” times. The IAGWs could extend their energies into higher layers beyond exobase due to a thermospheric layer expansion(i.e., density increase) during dust seasons.

Stochastic Surrogate Model for Meteotsunami Early Warning System in the Eastern Adriatic Sea

AbstractThe meteotsunami early warning system prototype using stochastic surrogate approach and running operationally in the eastern Adriatic Sea is presented. First, the atmospheric internal gravity waves (IGWs) driving the meteotsunamis are either forecasted with state‐of‐the‐art deterministic models at least a day in advance or detected through measurements at least 2 hr before the meteotsunami reaches sensitive locations. The extreme sea‐level hazard forecast at endangered locations is then derived with an innovative stochastic surrogate model—implemented with generalized polynomial chaos expansion (gPCE) method and synthetic IGWs forcing a barotropic ocean model—used with the input parameters extracted from deterministic model results and/or measurements. The evaluation of the system, both against five historical events and for all the detected potential meteotsunamis since late 2018 when the early warning system prototype became operational, reveals that the meteotsunami hazard is conservatively assessed but often overestimated at some locations. Despite some needed improvements and developments, this study demonstrates that gPCE‐based methods can be used for atmospherically driven extreme sea‐level hazard assessment and in geosciences in wide.

Atmospheric Internal Gravity Waves Caused by Tsunamis over Kuril Islands

MODIS (Aqua and Terra) space images of the northwest part of the Pacific Ocean at instants of considerable tsunamis in 2009–2011 have been analyzed. Periodic cloud structures typical for internal gravity waves (IGWs) in the atmosphere have been revealed in the region of the Kuril Islands in five cases. It has been shown that the meteorological conditions observed during those events favored the appearance of such phenomena. The continuous oceanic upwelling in the region of the Kuril–Kamchatka Trench is a favorable factor for IGW generation due to the creation of temperature contrasts observed both in warm and cold seasons between the ground layer of the atmosphere and ocean surface. The estimate of the structure of cloud manifestations of atmospheric waves by satellite images testifies also to the influence of the Kuril Ridge orography on their appearance and propagation over the water area under study. The increase in amplitudes and duration of oscillations caused by the tsunami in the shelf zone can be an auxiliary factor for the IGW generation over coastal territories.

On the GPS-based ionospheric perturbation after the Tohoku earthquake of March 11, 2011

Based on the data from the GPS receiving networks in Japan and America which have a high time resolution (2 min), two-dimensional (2D) distributions of the variations in the ionospheric total electron content (TEC) are constructed both close to and far from of the epicenter of the submarine earthquake of March 11, 2011 in Japan. Above the epicenter, a diverging multi-period disturbance appears after the main shock due to the acoustic gravity waves. Far from the epicenter, the wave trains associated with the tsunamigenic atmospheric internal gravity waves are revealed. These atmospheric waves significantly advance the arrival of the tsunami signal initially on the Hawaiian islands and then on the western coast of North America. The presence of the tsunami precursor in the form of atmospheric gravity waves is supported by the numerical calculations and by the analysis of the dispersion relation for the waves in the atmosphere. The detected ionospheric responses close and far from the epicenter can be used in the early tsunami warning systems.

TEC variations and ionospheric disturbances during the magnetic storm in March 2015 observed from continuous GPS data in the Southeast Asia region

TEC variations and ionospheric disturbances during the magnetic storm in March 2015 observed from continuous GPS data in the Southeast Asia region

Wind and Temperature Oscillations Generated by Wave–Turbulence Interactions in the Stably Stratified Boundary Layer

Abstract The authors investigate atmospheric internal gravity waves (IGWs): their generation and induction of global intermittent turbulence in the nocturnal stable atmospheric boundary layer based on the new concept of turbulence generation discussed in a prior paper by Sun et al. The IGWs are generated by air lifted by convergence forced by the colliding background flow and cold currents near the ground. The buoyancy-forced IGWs enhance wind speed at the wind speed wave crests such that the bulk shear instability generates large coherent eddies, which augment local turbulent mixing and vertically redistribute momentum and heat. The periodically enhanced turbulent mixing, in turn, modifies the air temperature and flow oscillations of the original IGWs. These turbulence-forced oscillations (TFOs) resemble waves and coherently transport momentum and sensible heat. The observed momentum and sensible heat fluxes at the IGW frequency, which are due to either the buoyancy-forced IGWs themselves or the TFOs, are larger than turbulent fluxes near the surface. The IGWs enhance not only the bulk shear at the wave crests, but also local shear over the wind speed troughs of the surface IGWs. Temporal and spatial variations of turbulent mixing as a result of this wave-induced turbulent mixing change the mean airflow and the shape of the IGWs.

Meteorological waves (by Ocean Color Scanner Data)

Data of normalized water leaving radiance at a wavelength 859 nm Lwn(859) of 250-m spatial resolution obtained from Moderate Ocean Color Scanners (MODIS) installed on Aqua and Terra satellites were used to study meteorological waves. These waves are caused by atmospheric internal gravity waves at the expense of a change of atmospheric pressure impacting the sea surface and bringing a change in its level; they are observable everywhere in the ocean. Examples of meteorological waves were considered for the eastern part of the Black Sea, where they appeared as stripes of alternate brightness on Lwn(859) images. It is shown that meteorological waves at one and the same place can be totally generated by atmospheric waves spreading at different heights of the lower troposphere. The 3D characteristics of meteorological waves were evaluated including the direction of wave propagation, crest length reaching more than one hundred kilometers, wavelength of several tens centimeters, and wave amplitude of several tens of centimeters. For conditions of intermittent cloudiness, imposition in a difference mode of the level L1b radiance image with the signature of atmospheric waves in a cloud and of the level L2 water leaving the radiance image with the signature of meteorological waves enabled us to examine the phase structure of waves and to reveal the existence of resonance.

A statistical analysis on the relationship between thunderstorms and the sporadic E Layer over Rome

AbstractMeteorological processes (cold fronts, mesoscale convective complexes, thunderstorms) in the troposphere can generate upward propagating waves in the neutral atmosphere affecting the behaviour of the ionosphere. One type of these waves are the internal atmospheric gravity waves (AGWs) which are often generated by thunderstorms. Davis & Johnson (2005) found in low pressure systems that a localized intensification of the sporadic E layer (Es) can be attributed to lightnings. To confirm this result, we have performed two different statistical analysis using the time series of the critical frequency (foEs), the virtual height of the sporadic E layer (h'Es), and meteorological observations (lightnings, Infrared maps) over the ionospheric station of Rome (41.9° N, 12.5° E). In the first statistical analysis, we separated the days of 2009 into two groups: stormy days and fair‐weather days, then we studied the occurrence and the properties of the Es separately for the two different groups. No significant differences have been found. In the second case, a superposed epoch analysis (SEA) was used to study the behaviour of the critical frequency and virtual height 100 hours before and after the lightnings. The SEA shows a statistically significant decrease in the critical frequency after the time of the lightnings, which indicates a sudden decrease in the electron density of the sporadic E layer associated with lightnings. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A method for specifying atmospheric gravity wavefields for long‐range infrasound propagation calculations

AbstractTwo important challenges in infrasound propagation physics are (1) to explain frequently observed infrasound signals in the classical near‐field shadow zones and (2) to accurately predict observed waveform amplitude and signal duration. For these problems, the role that small‐scale internal atmospheric gravity wave fluctuations play has recently been realized. This paper provides a methodology for representing small‐scale internal gravity wave fluctuations which is suitable for infrasound propagation calculations. Adapted from the numerical weather prediction and climate modeling communities, the resulting stochastic gravity wave noise field model is three‐dimensional, time dependent, and self‐consistent with the atmospheric background state. To illustrate the methodology the resultant gravity wavefields are applied to ray‐trace simulations of observed infrasound travel times for a dense seismic network in the Western United States which recorded infrasound signals from a large surface explosion.

Synthetic Aperture Radar Remote Sensing of Shear-Driven Atmospheric Internal Gravity Waves in the Vicinity of a Warm Front

Abstract The synthetic aperture radar ocean surface signature of atmospheric internal gravity waves in the vicinity of a synoptic-scale warm front is examined via a classic Kelvin–Helmholtz velocity profile with a rigid lower boundary and a sloping interface. The horizontal distance that the waves extend from the surface warm front is consistent with a bifurcation along the warm frontal inversion from unstable to neutral solutions. Similarity theories are derived for the wave span and the location of maximum growth rate relative to the surface front position. The theoretical maximum wave growth rate is demonstrated to occur near this bifurcation point and, hence, to explain the observed pattern of wave amplitude. Finally, a wave crest-tracing procedure is developed to explain the observed acute orientation of waves with respect to the surface warm front.

The 2009 Samoa and 2010 Chile tsunamis as observed in the ionosphere using GPS total electron content

[1] Ground-based Global Positioning System (GPS) measurements of ionospheric total electron content (TEC) show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following two recent seismic events: the Samoa earthquake of 29 September 2009 and the Chile earthquake of 27 February 2010. Both earthquakes produced ocean tsunamis that were destructive to coastal communities near the epicenters, and both were observed in tidal gauge and buoy measurements throughout the Pacific Ocean. We observe fluctuations in TEC correlated in time, space, and wave properties with these tsunamis using the Jet Propulsion Laboratory's Global Ionospheric Mapping software. These TEC measurements were band-pass filtered to remove ionospheric TEC variations with wavelengths and periods outside the typical range for tsunamis. Observable variations in TEC appear correlated with the tsunamis in some locations (Hawaii and Japan), but not in others (Southern California or near the epicenters). Where variations are observed, the typical amplitude tends to be ∼0.1–0.2 TEC units for these events, on the order of ∼1% of the background TEC value. These observations are compared to estimates of expected tsunami-driven TEC variations produced by Embry Riddle Aeronautical University's Spectral Full Wave Model, an atmosphere-ionosphere coupled model, and are found to be in good agreement. Significant TEC variations are not always seen when a tsunami is present, but in these two events the regions where a strong ocean tsunami was observed coincided with clear TEC observations, while a lack of clear TEC observations coincided with smaller sea surface height amplitudes. There exists the potential to apply these detection techniques to real-time GPS TEC data, providing estimates of tsunami speed and amplitude that may be useful for early warning systems.

Influence of the boundary layer development on the ozone concentration over an urban area

Results obtained during two campaigns (summer 2004 and autumn 2005) of observation of the planetary boundary layer dynamics over the Sofia city urban area are presented. An EARLINET scanning aerosol lidar, an ozone analyser and a ground meteorological station were used during the observations. The stable boundary layer height varied from 200 m to 600 m during the different seasons. The residual layer was found to be at 700–1200 m, being destroyed between 10:30 and 12:30 LST. The mixing layer developed up to heights of about 800–1300 m. The ground level ozone concentration was measured to be from 10 µg/m3 to 90 µg/m3. The convective boundary layer formation in three case studies (a clear sunny day, a partial solar eclipse, and in the presence of internal atmospheric gravity waves) are presented. In particular, the mixing layer development and the residual layer destruction are studied and considered, along with the relevant ground level ozone concentration variation.