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1
Nishida, Kiwamu, Naoki Kobayashi, and Yoshio Fukao. "Background Lamb waves in the Earth's atmosphere." Geophysical Journal International 196, no. 1 (November 5, 2013): 312–16. http://dx.doi.org/10.1093/gji/ggt413.
Повний текст джерелаАнотація:
Abstract Lamb waves of the Earth's atmosphere in the millihertz band have been considered as transient phenomena excited only by large events. Here, we show the first evidence of background Lamb waves in the Earth's atmosphere from 0.2 to 10 mHz, based on the array analysis of microbarometer data from the USArray in 2012. The observations suggest that the probable excitation source is atmospheric turbulence in the troposphere. Theoretically, their energy in the troposphere tunnels into the thermosphere at a resonant frequency via thermospheric gravity wave, where the observed amplitudes indeed take a local minimum. The energy leak through the frequency window could partly contribute to thermospheric wave activity.
2
Jesch, David, Alexander S. Medvedev, Francesco Castellini, Erdal Yiğit, and Paul Hartogh. "Density Fluctuations in the Lower Thermosphere of Mars Retrieved From the ExoMars Trace Gas Orbiter (TGO) Aerobraking." Atmosphere 10, no. 10 (October 15, 2019): 620. http://dx.doi.org/10.3390/atmos10100620.
Повний текст джерелаАнотація:
The upper atmosphere of Mars is constantly perturbed by small-scale gravity waves propagating from below. As gravity waves strongly affect the large-scale dynamics and thermal state, constraining their statistical characteristics is of great importance for modeling the atmospheric circulation. We present a new data set of density perturbation amplitudes derived from accelerometer measurements during aerobraking of the European Space Agency’s Trace Gas Orbiter. The obtained data set presents features found by three previous orbiters: the lower thermosphere polar warming in the winter hemisphere, and the lack of links between gravity wave activity and topography. In addition, the orbits allowed for demonstrating a very weak diurnal variability in wave activity at high latitudes of the southern winter hemisphere for the first time. The estimated vertical damping rates of gravity waves agree well with theoretical predictions. No clear anticorrelation between perturbation amplitudes and the background temperature has been found. This indicates differences in dissipation mechanisms of gravity waves in the lower and upper thermosphere.
3
Ford, E. A. K., A. L. Aruliah, E. M. Griffin, and I. McWhirter. "High time resolution measurements of the thermosphere from Fabry-Perot Interferometer measurements of atomic oxygen." Annales Geophysicae 25, no. 6 (June 29, 2007): 1269–78. http://dx.doi.org/10.5194/angeo-25-1269-2007.
Повний текст джерелаАнотація:
Abstract. Recent advances in the performance of CCD detectors have enabled a high time resolution study of the high latitude upper thermosphere with Fabry-Perot Interferometers (FPIs) to be performed. 10-s integration times were used during a campaign in April 2004 on an FPI located in northern Sweden in the auroral oval. The FPI is used to study the thermosphere by measuring the oxygen red line emission at 630.0 nm, which emits at an altitude of approximately 240 km. Previous time resolutions have been 4 min at best, due to the cycle of look directions normally observed. By using 10 s rather than 40 s integration times, and by limiting the number of full cycles in a night, high resolution measurements down to 15 s were achievable. This has allowed the maximum variability of the thermospheric winds and temperatures, and 630.0 nm emission intensities, at approximately 240 km, to be determined as a few minutes. This is a significantly greater variability than the often assumed value of 1 h or more. A Lomb-Scargle analysis of this data has shown evidence of gravity wave activity with waves with short periods. Gravity waves are an important feature of mesosphere-lower thermosphere (MLT) dynamics, observed using many techniques and providing an important mechanism for energy transfer between atmospheric regions. At high latitudes gravity waves may be generated in-situ by localised auroral activity. Short period waves were detected in all four clear nights when this experiment was performed, in 630.0 nm intensities and thermospheric winds and temperatures. Waves with many periodicities were observed, from periods of several hours, down to 14 min. These waves were seen in all parameters over several nights, implying that this variability is a typical property of the thermosphere.
4
Becker, Erich. "Mean-Flow Effects of Thermal Tides in the Mesosphere and Lower Thermosphere." Journal of the Atmospheric Sciences 74, no. 6 (June 1, 2017): 2043–63. http://dx.doi.org/10.1175/jas-d-16-0194.1.
Повний текст джерелаАнотація:
Abstract This study addresses the heat budget of the mesosphere and lower thermosphere with regard to the energy deposition of upward-propagating waves. To this end, the energetics of gravity waves are recapitulated using an anelastic version of the primitive equations. This leads to an expression for the energy deposition of waves that is usually resolved in general circulation models. The energy deposition is shown to be mainly due to the frictional heating and, additionally, due to the negative buoyancy production of wave kinetic energy. The frictional heating includes contributions from horizontal and vertical momentum diffusion, as well as from ion drag. This formalism is applied to analyze results from a mechanistic middle-atmosphere general circulation model that includes energetically consistent parameterizations of diffusion, gravity waves, and ion drag. This paper estimates 1) the wave driving and energy deposition of thermal tides, 2) the model response to the excitation of thermal tides, and 3) the model response to the combined energy deposition by parameterized gravity waves and resolved waves. It is found that thermal tides give rise to a significant energy deposition in the lower thermosphere. The temperature response to thermal tides is positive. It maximizes at polar latitudes in the lower thermosphere as a result of poleward circulation branches that are driven by the predominantly westward Eliassen–Palm flux divergence of the tides. In addition, thermal tides give rise to a downward shift and reduction of the gravity wave drag in the upper mesosphere. Including the energy deposition in the model causes a substantial warming in the upper mesosphere and lower thermosphere.
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Broutman, Dave, Stephen D. Eckermann, and Douglas P. Drob. "The Partial Reflection of Tsunami-Generated Gravity Waves." Journal of the Atmospheric Sciences 71, no. 9 (August 28, 2014): 3416–26. http://dx.doi.org/10.1175/jas-d-13-0309.1.
Повний текст джерелаАнотація:
Abstract A vertical eigenfunction equation is solved to examine the partial reflection and partial transmission of tsunami-generated gravity waves propagating through a height-dependent background atmosphere from the ocean surface into the lower thermosphere. There are multiple turning points for each vertical eigenfunction (at least eight in one example), yet the wave transmission into the thermosphere is significant. Examples are given for gravity wave propagation through an idealized wind jet centered near the mesopause and through a realistic vertical profile of wind and temperature relevant to the tsunami generated by the Sumatra earthquake on 26 December 2004.
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Robinson, T. R. "Acoustic gravity wave growth and damping in convecting plasma." Annales Geophysicae 12, no. 2/3 (January 31, 1994): 210–19. http://dx.doi.org/10.1007/s00585-994-0210-5.
Повний текст джерелаАнотація:
Abstract. The propagation of acoustic gravity waves through steadily convecting plasma in the thermosphere has been analysed theoretically. The growth and damping rates of internal gravity waves due to the feedback effects of wave-modulated Joule heating and Laplace forcing have been calculated. It is found that large convection flow velocities lead to the growth of large-scale internal gravity waves, whilst small- and medium-scale waves are heavily damped, under similar conditions. It has also been shown that wave growth is favoured for waves travelling against the plasma flow direction. The effects of critical coupling when wave phase speeds match the plasma flow speed have also been investigated. The results of these calculations are discussed in the context of the atmospheric energy budget and thermosphere-ionosphere coupling.
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Li, Qinzeng, Jiyao Xu, Hanli Liu, Xiao Liu, and Wei Yuan. "How do gravity waves triggered by a typhoon propagate from the troposphere to the upper atmosphere?" Atmospheric Chemistry and Physics 22, no. 18 (September 19, 2022): 12077–91. http://dx.doi.org/10.5194/acp-22-12077-2022.
Повний текст джерелаАнотація:
Abstract. Gravity waves (GWs) strongly affect atmospheric dynamics and photochemistry and the coupling between the troposphere, stratosphere, mesosphere, and thermosphere. In addition, GWs generated by strong disturbances in the troposphere (e.g. thunderstorms and typhoons) can affect the atmosphere of Earth from the troposphere to the thermosphere. However, the fundamental process of GW propagation from the troposphere to the thermosphere is poorly understood because it is challenging to constrain this process using observations. Moreover, GWs tend to dissipate rapidly in the thermosphere because the molecular diffusion increases exponentially with height. In this study, a double-layer airglow network was used to capture concentric GWs (CGWs) over China that were excited by Typhoon Chaba (2016). We used ERA5 reanalysis data and Multi-functional Transport Satellite-1R observations to quantitatively describe the propagation processes of typhoon-generated CGWs from the troposphere, through the stratosphere and mesosphere, to the thermosphere. We found that the CGWs in the mesopause region were generated directly by the typhoon in the troposphere. However, the backward-ray-tracing analysis suggested that CGWs in the thermosphere originated from the secondary waves generated by the dissipation of the CGW and/or nonlinear processes in the mesopause region.
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Yasui, Ryosuke, Kaoru Sato, and Yasunobu Miyoshi. "The Momentum Budget in the Stratosphere, Mesosphere, and Lower Thermosphere. Part II: The In Situ Generation of Gravity Waves." Journal of the Atmospheric Sciences 75, no. 10 (October 2018): 3635–51. http://dx.doi.org/10.1175/jas-d-17-0337.1.
Повний текст джерелаАнотація:
The contributions of gravity waves to the momentum budget in the mesosphere and lower thermosphere (MLT) is examined using simulation data from the Ground-to-Topside Model of Atmosphere and Ionosphere for Aeronomy (GAIA) whole-atmosphere model. Regardless of the relatively coarse model resolution, gravity waves appear in the MLT region. The resolved gravity waves largely contribute to the MLT momentum budget. A pair of positive and negative Eliassen–Palm flux divergences of the resolved gravity waves are observed in the summer MLT region, suggesting that the resolved gravity waves are likely in situ generated in the MLT region. In the summer MLT region, the mean zonal winds have a strong vertical shear that is likely formed by parameterized gravity wave forcing. The Richardson number sometimes becomes less than a quarter in the strong-shear region, suggesting that the resolved gravity waves are generated by shear instability. In addition, shear instability occurs in the low (middle) latitudes of the summer (winter) MLT region and is associated with diurnal (semidiurnal) migrating tides. Resolved gravity waves are also radiated from these regions. In Part I of this paper, it was shown that Rossby waves in the MLT region are also radiated by the barotropic and/or baroclinic instability formed by parameterized gravity wave forcing. These results strongly suggest that the forcing by gravity waves originating from the lower atmosphere causes the barotropic/baroclinic and shear instabilities in the mesosphere that, respectively, generate Rossby and gravity waves and suggest that the in situ generation and dissipation of these waves play important roles in the momentum budget of the MLT region.
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Paulino, Igo, Joyrles F. Moraes, Gleuson L. Maranhão, Cristiano M. Wrasse, Ricardo Arlen Buriti, Amauri F. Medeiros, Ana Roberta Paulino, et al. "Intrinsic parameters of periodic waves observed in the OI6300 airglow layer over the Brazilian equatorial region." Annales Geophysicae 36, no. 1 (February 28, 2018): 265–73. http://dx.doi.org/10.5194/angeo-36-265-2018.
Повний текст джерелаАнотація:
Abstract. Periodic waves were observed in the OI6300 airglow images over São João do Cariri (36.5∘ W, 7.4∘ S) from 2012 to 2014 with simultaneous observations of the thermospheric wind using two Fabry–Pérot interferometers (FPIs). The FPIs measurements were carried out at São João do Cariri and Cajazeiras (38.5∘ W, 6.9∘ S). The observed spectral characteristics of these waves (period and wavelength) as well the propagation direction were estimated using two-dimensional Fourier analysis in the airglow images. The horizontal thermospheric wind was calculated from the Doppler shift of the OI6300 data extracted from interference fringes registered by the FPIs. Combining these two techniques, the intrinsic parameters of the periodic waves were estimated and analyzed. The spectral parameters of the periodic waves were quite similar to the previous observations at São João do Cariri. The intrinsic periods for most of the waves were shorter than the observed periods, as a consequence, the intrinsic phase speeds were faster compared to the observed phase speeds. As a consequence, these waves can easily propagate into the thermosphere–ionosphere since the fast gravity waves can skip turning and critical levels. The strength and direction of the wind vector in the thermosphere must be the main cause for the observed anisotropy in the propagation direction of the periodic waves, even if the sources of these waves are assumed to be isotropic. Keywords. Meteorology and atmospheric dynamics (waves and tides)
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Vargas, Fabio, Jorge L. Chau, Harikrishnan Charuvil Asokan, and Michael Gerding. "Mesospheric gravity wave activity estimated via airglow imagery, multistatic meteor radar, and SABER data taken during the SIMONe–2018 campaign." Atmospheric Chemistry and Physics 21, no. 17 (September 13, 2021): 13631–54. http://dx.doi.org/10.5194/acp-21-13631-2021.
Повний текст джерелаАнотація:
Abstract. We describe in this study the analysis of small and large horizontal-scale gravity waves from datasets composed of images from multiple mesospheric airglow emissions as well as multistatic specular meteor radar (MSMR) winds collected in early November 2018, during the SIMONe–2018 (Spread-spectrum Interferometric Multi-static meteor radar Observing Network) campaign. These ground-based measurements are supported by temperature and neutral density profiles from TIMED/SABER (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry) satellite in orbits near Kühlungsborn, northern Germany (54.1∘ N, 11.8∘ E). The scientific goals here include the characterization of gravity waves and their interaction with the mean flow in the mesosphere and lower thermosphere and their relationship to dynamical conditions in the lower and upper atmosphere. We have obtained intrinsic parameters of small- and large-scale gravity waves and characterized their impact in the mesosphere via momentum flux (FM) and momentum flux divergence (FD) estimations. We have verified that a small percentage of the detected wave events is responsible for most of FM measured during the campaign from oscillations seen in the airglow brightness and MSMR winds taken over 45 h during four nights of clear-sky observations. From the analysis of small-scale gravity waves (λh < 725 km) seen in airglow images, we have found FM ranging from 0.04–24.74 m2 s−2 (1.62 ± 2.70 m2 s−2 on average). However, small-scale waves with FM > 3 m2 s−2 (11 % of the events) transport 50 % of the total measured FM. Likewise, wave events of FM > 10 m2 s−2 (2 % of the events) transport 20 % of the total. The examination of large-scale waves (λh > 725 km) seen simultaneously in airglow keograms and MSMR winds revealed amplitudes > 35 %, which translates into FM = 21.2–29.6 m2 s−2. In terms of gravity-wave–mean-flow interactions, these large FM waves could cause decelerations of FD = 22–41 m s−1 d−1 (small-scale waves) and FD = 38–43 m s−1 d−1 (large-scale waves) if breaking or dissipating within short distances in the mesosphere and lower thermosphere region.
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Gumbel, Jörg, Linda Megner, Ole Martin Christensen, Nickolay Ivchenko, Donal P. Murtagh, Seunghyuk Chang, Joachim Dillner, et al. "The MATS satellite mission – gravity wave studies by Mesospheric Airglow/Aerosol Tomography and Spectroscopy." Atmospheric Chemistry and Physics 20, no. 1 (January 13, 2020): 431–55. http://dx.doi.org/10.5194/acp-20-431-2020.
Повний текст джерелаАнотація:
Abstract. Global three-dimensional data are a key to understanding gravity waves in the mesosphere and lower thermosphere. MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) is a new Swedish satellite mission that addresses this need. It applies space-borne limb imaging in combination with tomographic and spectroscopic analysis to obtain gravity wave data on relevant spatial scales. Primary measurement targets are O2 atmospheric band dayglow and nightglow in the near infrared, and sunlight scattered from noctilucent clouds in the ultraviolet. While tomography provides horizontally and vertically resolved data, spectroscopy allows analysis in terms of mesospheric temperature, composition, and cloud properties. Based on these dynamical tracers, MATS will produce a climatology on wave spectra during a 2-year mission. Major scientific objectives include a characterization of gravity waves and their interaction with larger-scale waves and mean flow in the mesosphere and lower thermosphere, as well as their relationship to dynamical conditions in the lower and upper atmosphere. MATS is currently being prepared to be ready for a launch in 2020. This paper provides an overview of scientific goals, measurement concepts, instruments, and analysis ideas.
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Benna, M., S. W. Bougher, Y. Lee, K. J. Roeten, E. Yiğit, P. R. Mahaffy, and B. M. Jakosky. "Global circulation of Mars’ upper atmosphere." Science 366, no. 6471 (December 12, 2019): 1363–66. http://dx.doi.org/10.1126/science.aax1553.
Повний текст джерелаАнотація:
The thermosphere of Mars is the interface through which the planet is continuously losing its reservoir of atmospheric volatiles to space. The structure and dynamics of the thermosphere is driven by a global circulation that redistributes the incident energy from the Sun. We report mapping of the global circulation in the thermosphere of Mars with the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. The measured neutral winds reveal circulation patterns simpler than those of Earth that persist over changing seasons. The winds exhibit pronounced correlation with the underlying topography owing to orographic gravity waves.
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Becker, Erich, and Charles McLandress. "Consistent Scale Interaction of Gravity Waves in the Doppler Spread Parameterization." Journal of the Atmospheric Sciences 66, no. 5 (May 1, 2009): 1434–49. http://dx.doi.org/10.1175/2008jas2810.1.
Повний текст джерелаАнотація:
Abstract The standard Doppler spread parameterization of gravity waves, which was proposed by C.-O. Hines and has been applied in a number of middle atmosphere general circulation models, is extended by the inclusion of all effects associated with vertical diffusion. Here the Wentzel–Kramers–Brillouin (WKB) approximation is employed to calculate the vertical propagation of the wave spectrum in the presence of wave damping. According to the scale interaction between quasi-stationary turbulence and the larger nonturbulent flow, all vertical diffusion applied to the resolved flow should damp the parameterized gravity waves as well. Hence, the unobliterated part of the gravity wave spectrum is subject to diffusive damping by the following processes: 1) the background diffusion derived from the model’s boundary layer vertical diffusion scheme, which may extend into the middle atmosphere, 2) molecular diffusion, and 3) the turbulent diffusion resulting from the truncation of the gravity wave spectrum by Doppler spreading, which thus feeds back on the unobliterated gravity waves. The extended Doppler spread parameterization is examined using perpetual July simulations performed with a mechanistic general circulation model. For reasonable parameter settings, the convergence of the potential temperature flux cannot be neglected in the sensible heat budget, especially in the thermosphere. Less gravity wave flux enters the model thermosphere when vertical diffusion is included, thus avoiding the need for artificial means to control the parameterized gravity waves in the upper atmosphere. The zonal wind in the tropical middle and upper atmosphere is found to be especially sensitive to gravity wave damping by diffusion.
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Hocke, K., and K. Schlegel. "A review of atmospheric gravity waves and travelling ionospheric disturbances: 1982-1995." Annales Geophysicae 14, no. 9 (September 30, 1996): 917–40. http://dx.doi.org/10.1007/s00585-996-0917-6.
Повний текст джерелаАнотація:
Abstract. Recent investigations of atmospheric gravity waves (AGW) and travelling ionospheric disturbances (TID) in the Earth\\'s thermosphere and ionosphere are reviewed. In the past decade, the generation of gravity waves at high latitudes and their subsequent propagation to low latitudes have been studied by several global model simulations and coordinated observation campaigns such as the Worldwide Atmospheric Gravity-wave Study (WAGS), the results are presented in the first part of the review. The second part describes the progress towards understanding the AGW/TID characteristics. It points to the AGW/TID relationship which has been recently revealed with the aid of model-data comparisons and by the application of new inversion techniques. We describe the morphology and climatology of gravity waves and their ionospheric manifestations, TIDs, from numerous new observations.
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Ford, E. A. K., A. L. Aruliah, E. M. Griffin, and I. McWhirter. "Thermospheric gravity waves in Fabry-Perot Interferometer measurements of the 630.0nm OI line." Annales Geophysicae 24, no. 2 (March 23, 2006): 555–66. http://dx.doi.org/10.5194/angeo-24-555-2006.
Повний текст джерелаАнотація:
Abstract. Gravity waves are an important feature of mesosphere - lower thermosphere (MLT) dynamics, observed using many techniques and providing an important mechanism for energy transfer between atmospheric regions. It is known that some gravity waves may propagate through the mesopause and reach greater altitudes before eventually "breaking" and depositing energy. The generation, propagation, and breaking of upper thermospheric gravity waves have not been studied directly often. However, their ionospheric counterparts, travelling ionospheric disturbances (TIDs), have been extensively studied in, for example, radar data. At high latitudes, it is believed localised auroral activity may generate gravity waves in-situ. Increases in sensor efficiency of Fabry-Perot Interferometers (FPIs) located in northern Scandinavia have provided higher time resolution measurements of the auroral oval and polar cap atomic oxygen red line emission at 630.0 nm. A Lomb-Scargle analysis of this data has shown evidence of gravity wave activity with periods ranging from a few tens of minutes to several hours. Oscillations are seen in the intensity of the line as well as the temperatures and line of sight winds. Instruments are located in Sodankylä, Finland; Kiruna, Sweden; Skibotn, Norway, and Svalbard in the Arctic Ocean. A case study is presented here, where a wave of 1.8 h period has a phase speed of 250 ms-1 with a propagation angle of 302°, and a horizontal wavelength of 1600 km. All the FPIs are co-located with EISCAT radars, as well as being supplemented by a range of other instrumentation. This allows the waves found in the FPI data to be put in context with the ionosphere and atmosphere system. Consequently, the source region of the gravity waves can be determined.
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Barrow, Daniel, Katia I. Matcheva, and Pierre Drossart. "Prospects for observing atmospheric gravity waves in Jupiter’s thermosphere using emission." Icarus 219, no. 1 (May 2012): 77–85. http://dx.doi.org/10.1016/j.icarus.2012.02.007.
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England, S. L., G. Liu, E. Yiğit, P. R. Mahaffy, M. Elrod, M. Benna, H. Nakagawa, N. Terada, and B. Jakosky. "MAVEN NGIMS observations of atmospheric gravity waves in the Martian thermosphere." Journal of Geophysical Research: Space Physics 122, no. 2 (February 2017): 2310–35. http://dx.doi.org/10.1002/2016ja023475.
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Trinh, Quang Thai, Manfred Ern, Eelco Doornbos, Peter Preusse, and Martin Riese. "Satellite observations of middle atmosphere–thermosphere vertical coupling by gravity waves." Annales Geophysicae 36, no. 2 (March 19, 2018): 425–44. http://dx.doi.org/10.5194/angeo-36-425-2018.
Повний текст джерелаАнотація:
Abstract. Atmospheric gravity waves (GWs) are essential for the dynamics of the middle atmosphere. Recent studies have shown that these waves are also important for the thermosphere/ionosphere (T/I) system. Via vertical coupling, GWs can significantly influence the mean state of the T/I system. However, the penetration of GWs into the T/I system is not fully understood in modeling as well as observations. In the current study, we analyze the correlation between GW momentum fluxes observed in the middle atmosphere (30–90 km) and GW-induced perturbations in the T/I. In the middle atmosphere, GW momentum fluxes are derived from temperature observations of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite instrument. In the T/I, GW-induced perturbations are derived from neutral density measured by instruments on the Gravity field and Ocean Circulation Explorer (GOCE) and CHAllenging Minisatellite Payload (CHAMP) satellites. We find generally positive correlations between horizontal distributions at low altitudes (i.e., below 90 km) and horizontal distributions of GW-induced density fluctuations in the T/I (at 200 km and above). Two coupling mechanisms are likely responsible for these positive correlations: (1) fast GWs generated in the troposphere and lower stratosphere can propagate directly to the T/I and (2) primary GWs with their origins in the lower atmosphere dissipate while propagating upwards and generate secondary GWs, which then penetrate up to the T/I and maintain the spatial patterns of GW distributions in the lower atmosphere. The mountain-wave related hotspot over the Andes and Antarctic Peninsula is found clearly in observations of all instruments used in our analysis. Latitude–longitude variations in the summer midlatitudes are also found in observations of all instruments. These variations and strong positive correlations in the summer midlatitudes suggest that GWs with origins related to convection also propagate up to the T/I. Different processes which likely influence the vertical coupling are GW dissipation, possible generation of secondary GWs, and horizontal propagation of GWs. Limitations of the observations as well as of our research approach are discussed. Keywords. Ionosphere (ionosphere–atmosphere interactions)
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Fritts, D. C., and S. L. Vadas. "Gravity wave penetration into the thermosphere: sensitivity to solar cycle variations and mean winds." Annales Geophysicae 26, no. 12 (December 2, 2008): 3841–61. http://dx.doi.org/10.5194/angeo-26-3841-2008.
Повний текст джерелаАнотація:
Abstract. We previously considered various aspects of gravity wave penetration and effects at mesospheric and thermospheric altitudes, including propagation, viscous effects on wave structure, characteristics, and damping, local body forcing, responses to solar cycle temperature variations, and filtering by mean winds. Several of these efforts focused on gravity waves arising from deep convection or in situ body forcing accompanying wave dissipation. Here we generalize these results to a broad range of gravity wave phase speeds, spatial scales, and intrinsic frequencies in order to address all of the major gravity wave sources in the lower atmosphere potentially impacting the thermosphere. We show how penetration altitudes depend on gravity wave phase speed, horizontal and vertical wavelengths, and observed frequencies for a range of thermospheric temperatures spanning realistic solar conditions and winds spanning reasonable mean and tidal amplitudes. Our results emphasize that independent of gravity wave source, thermospheric temperature, and filtering conditions, those gravity waves that penetrate to the highest altitudes have increasing vertical wavelengths and decreasing intrinsic frequencies with increasing altitude. The spatial scales at the highest altitudes at which gravity wave perturbations are observed are inevitably horizontal wavelengths of ~150 to 1000 km and vertical wavelengths of ~150 to 500 km or more, with the larger horizontal scales only becoming important for the stronger Doppler-shifting conditions. Observed and intrinsic periods are typically ~10 to 60 min and ~10 to 30 min, respectively, with the intrinsic periods shorter at the highest altitudes because of preferential penetration of GWs that are up-shifted in frequency by thermospheric winds.
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Vargas, Fabio, Guotao Yang, Paulo Batista, and Delano Gobbi. "Growth Rate of Gravity Wave Amplitudes Observed in Sodium Lidar Density Profiles and Nightglow Image Data." Atmosphere 10, no. 12 (November 28, 2019): 750. http://dx.doi.org/10.3390/atmos10120750.
Повний текст джерелаАнотація:
Amplitude growth rates of quasi-monochromatic gravity waves were estimated and compared from multiple instrument measurements carried out in Brazil. Gravity wave parameters, such as the wave amplitude and growth rate in distinct altitudes, were derived from sodium lidar density and nightglow all-sky images. Lidar observations were carried out in São Jose dos Campos (23 ∘ S, 46 ∘ W) from 1994 to 2004, while all-sky imagery of multiple airglow layers was conducted in Cachoeira Paulista (23 ∘ S, 45 ∘ W) from 1999–2000 and 2004–2005. We have found that most of the measured amplitude growth rates indicate dissipative behavior for gravity waves identified in both lidar profiles and airglow image datasets. Only a small fraction of the observed wave events (4% imager; 9% lidar) are nondissipative (freely propagating waves). Our findings also show that imager waves are strongly dissipated within the mesosphere and lower thermosphere region (MLT), decaying in amplitude in short distances (<12 km), while lidar waves tend to maintain a constant amplitude within that region. Part of the observed waves (16% imager; 36% lidar) showed unchanging amplitude with altitude (saturated waves). About 51.6% of the imager waves present strong attenuation (overdamped waves) in contrast with 9% of lidar waves. The general saturated or damped behavior is consistent with diffusive filtering processes imposing limits to amplitude growth rates of the observed gravity waves.
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Reichert, Robert, Bernd Kaifler, Natalie Kaifler, Markus Rapp, Pierre-Dominique Pautet, Michael J. Taylor, Alexander Kozlovsky, Mark Lester, and Rigel Kivi. "Retrieval of intrinsic mesospheric gravity wave parameters using lidar and airglow temperature and meteor radar wind data." Atmospheric Measurement Techniques 12, no. 11 (November 19, 2019): 5997–6015. http://dx.doi.org/10.5194/amt-12-5997-2019.
Повний текст джерелаАнотація:
Abstract. We analyse gravity waves in the upper-mesosphere, lower-thermosphere region from high-resolution temperature variations measured by the Rayleigh lidar and OH temperature mapper. From this combination of instruments, aided by meteor radar wind data, the full set of ground-relative and intrinsic gravity wave parameters are derived by means of the novel WAPITI (Wavelet Analysis and Phase line IdenTIfication) method. This WAPITI tool decomposes the gravity wave field into its spectral component while preserving the temporal resolution, allowing us to identify and study the evolution of gravity wave packets in the varying backgrounds. We describe WAPITI and demonstrate its capabilities for the large-amplitude gravity wave event on 16–17 December 2015 observed at Sodankylä, Finland, during the GW-LCYCLE-II (Gravity Wave Life Cycle Experiment) field campaign. We present horizontal and vertical wavelengths, phase velocities, propagation directions and intrinsic periods including uncertainties. The results are discussed for three main spectral regions, representing small-, medium- and large-period gravity waves. We observe a complex superposition of gravity waves at different scales, partly generated by gravity wave breaking, evolving in accordance with a vertically and presumably also horizontally sheared wind.
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Lund, Thomas S., David C. Fritts, Kam Wan, Brian Laughman, and Han-Li Liu. "Numerical Simulation of Mountain Waves over the Southern Andes. Part I: Mountain Wave and Secondary Wave Character, Evolutions, and Breaking." Journal of the Atmospheric Sciences 77, no. 12 (December 2020): 4337–56. http://dx.doi.org/10.1175/jas-d-19-0356.1.
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AbstractThis paper addresses the compressible nonlinear dynamics accompanying increasing mountain wave (MW) forcing over the southern Andes and propagation into the mesosphere and lower thermosphere (MLT) under winter conditions. A stretched grid provides very high resolution of the MW dynamics in a large computational domain. A slow increase of cross-mountain winds enables MWs to initially break in the mesosphere and extend to lower and higher altitudes thereafter. MW structure and breaking is strongly modulated by static mean and semidiurnal tide fields exhibiting a critical level at ~114 km for zonal MW propagation. Varying vertical group velocities for different zonal wavelengths λx yield initial breaking in the lee of the major Andes peaks for λx ~ 50 km, and extending significantly upstream for larger λx approaching the critical level at later times. The localized extent of the Andes terrain in latitude leads to “ship wave” responses above the individual peaks at earlier times, and a much larger ship-wave response at 100 km and above as the larger-scale MWs achieve large amplitudes. Other responses above regions of MW breaking include large-scale secondary gravity waves and acoustic waves that achieve very large amplitudes extending well into the thermosphere. MW breaking also causes momentum deposition that yields local decelerations initially, which merge and extend horizontally thereafter and persist throughout the event. Companion papers examine the associated momentum fluxes, mean-flow evolution, gravity wave–tidal interactions, and the MW instability dynamics and sources of secondary gravity waves and acoustic waves.
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Portnyagin, Y. I., J. M. Forbes, E. G. Merzlyakov, N. A. Makarov, and S. E. Palo. "Intradiurnal wind variations observed in the lower thermosphere over the South Pole." Annales Geophysicae 18, no. 5 (May 31, 2000): 547–54. http://dx.doi.org/10.1007/s00585-000-0547-3.
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Abstract. The first meteor radar measurements of meridional winds in the lower thermosphere (about 95 ± 5 km), along four azimuth directions: 0°, 90°E, 180° and 90°W; approximately 2° from the geographic South Pole were made during two observational campaigns: January 19, 1995-January 26, 1996, and November 21, 1996-January 27, 1997. Herein we report analyses of the measurement results, obtained during the first campaign, which cover the whole one-year period, with particular emphasis on the transient nature and seasonal behavior of the main parameters of the intradiurnal wind oscillations. To analyze the data, two complementary methods are used: the well-known periodogram (FFT) technique and the S-transform technique. The most characteristic periods of the intradiurnal oscillations are found to be rather uniformly spread between about 7 h and 12 h. All of these oscillations are westward-propagating with zonal wave number s=1 and their usual duration is confined to several periods. During the austral winter season the oscillations with periods less than 12 h are the most intensive, while during summer season the 12-h oscillations dominate. Lamb waves and internal-gravity wave propagation, non-linear interaction of the short-period tides, excitation in situ of the short period waves may be considered as possible processes which are responsible for intradiurnal wind oscillations in the lower thermosphere over South Pole.Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; waves and tides)
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Didebulidze, Goderdzi G., Giorgi Dalakishvili, and Maya Todua. "Formation of Multilayered Sporadic E under an Influence of Atmospheric Gravity Waves (AGWs)." Atmosphere 11, no. 6 (June 19, 2020): 653. http://dx.doi.org/10.3390/atmos11060653.
Повний текст джерелаАнотація:
The formation of multilayered sporadic E by atmospheric gravity waves (AGWs), propagating in the mid-latitude lower thermosphere, is shown theoretically and numerically. AGWs with a vertical wavelength smaller than the width of the lower thermosphere lead to the appearance of vertical drift velocity nodes (regions where the ions’ vertical drift velocity, caused by these waves, is zero) of heavy metallic ions (Fe+). The distance between the nearest nodes is close to the AGWs’ vertical wavelength. When the divergence of the ion vertical drift velocity at its nodes has a minimal negative value, then these charged particles can accumulate into Es-type thin layers and the formation of multilayered sporadic E is possible. We showed the importance of the ions’ ambipolar diffusion in the formation of Es layers and control of their densities. Oblique downward or upward propagation of AGWs causes downward or upward motion of the ion vertical drift velocity nodes by the vertical propagation phase velocity of these waves. In this case, the formed Es layers also descend or move upward with the same phase velocity. The condition, when the horizontal component of AGWs’ intrinsic phase velocity (phase velocity relative to the wind) and background wind velocity have same magnitudes but opposite directions, is favorable for the formation of the multilayered sporadic E at fixed heights of the sublayers. When the AGWs are absent, then horizontal homogeneous wind causes the formation of sporadic E but with a single peak. In the framework of the suggested theory, it is shown that, in the lower thermosphere, the wind direction, magnitude, and shear determine the development of the processes of ion/electron convergence into the Es-type layer, as well as their density divergence. Consideration of arbitrary height profiles of the meridional and zonal components of the horizontal wind velocity, in case of AGW propagation, should be important for the investigation of the distribution and behavior of heavy metallic ions on regional and global scales.
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Borchevkina, Olga P., Yuliya A. Kurdyaeva, Yurii A. Dyakov, Ivan V. Karpov, Gennady V. Golubkov, Pao K. Wang, and Maxim G. Golubkov. "Disturbances of the Thermosphere and the Ionosphere during a Meteorological Storm." Atmosphere 12, no. 11 (October 22, 2021): 1384. http://dx.doi.org/10.3390/atmos12111384.
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Determination of the physical mechanisms of energy transfer of tropospheric disturbances to the ionosphere is one of the fundamental problems of atmospheric physics. This article presents the results of observations carried out using two-wavelength lidar sensing at tropospheric altitudes and satellite GPS measurements during a meteorological storm in Kaliningrad (Russia, 54.7° N, 20.5° E) on 1 April 2016. During lidar sensing, it was found that the amplitudes of variations in atmospheric parameters with periods of acoustic (AWs) and internal gravity (IGWs) waves significantly increased. As a result of numerical modeling using the AtmoSym software package, it was shown that there is a noticeable increase in the period of temperature disturbances from 6–12 min to 10–17 min at altitudes from 150 km up to 230 km during the vertical propagation of acoustic waves and internal gravity waves from the troposphere. Nonlinear and dissipative processes in this layer lead to the formation of sources of secondary waves in the thermosphere with periods longer than those of primary ones. In this case, the unsteady nature of the wave source and the short duration of its operation does not lead to significant heating of the thermosphere. Simultaneous satellite observations demonstrate the response of the ionosphere (total electron content (TEC) disturbance) to tropospheric disturbances. Analysis of the time series of the amplitudes of the reflected lidar signal and TEC made it possible to determine that the response time of the ionosphere to tropospheric disturbances is 30–40 min.
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Fagundes, P. R., Y. Sahai, and J. A. Bittencourt. "Thermospheric zonal temperature gradients observed at low latitudes." Annales Geophysicae 19, no. 9 (September 30, 2001): 1133–39. http://dx.doi.org/10.5194/angeo-19-1133-2001.
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Abstract. Fabry-Perot interferometer (FPI) measurements of thermospheric temperatures from the Doppler widths of the OI 630 nm nightglow emission line have been carried out at Cachoeira Paulista (23° S, 45° W, 16° S dip latitude), Brazil. The east-west components of the thermospheric temperatures obtained on 73 nights during the period from 1988 to 1992, primarily under quiet geomagnetic conditions, were analyzed and are presented in this paper. It was observed that on 67% of these nights, the temperatures in both the east and west sectors presented similar values and nocturnal variations. However, during 33% of the nights, the observed temperatures in the west sector were usually higher than those observed in the east sector, with zonal temperature gradients in the range of 100 K to 600 K, over about an 800 km horizontal distance. Also, in some cases, the observed temperatures in the east and west sectors show different nocturnal variations. One of the possible sources considered for the observed zonal temperature gradients is the influence of gravity wave dissipation effects due to waves that propagate from lower altitudes to thermospheric heights. The observed zonal temperature gradients could also be produced by orographic gravity waves originated away, over the Andes Cordillera in the Pacific Sector, or by dissipation of orographic gravity waves generated over the Mantiqueira Mountains in the Atlantic sector by tropospheric disturbances (fronts and/or subtropical jet streams).Key words. Atmospheric composition and structure (air-glow and aurora; thermosphere - composition and chemistry) Ionosphere (equatorial ionosphere)
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Liu, H.-L., F. Sassi, and R. R. Garcia. "Error Growth in a Whole Atmosphere Climate Model." Journal of the Atmospheric Sciences 66, no. 1 (January 1, 2009): 173–86. http://dx.doi.org/10.1175/2008jas2825.1.
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Abstract It has been well established that the atmosphere is chaotic by nature and thus has a finite limit of predictability. The chaotic divergence of initial conditions and the predictability are explored here in the context of the whole atmosphere (from the ground to the thermosphere) using the NCAR Whole Atmosphere Community Climate Model (WACCM). From ensemble WACCM simulations, it is found that the early growth of differences in initial conditions is associated with gravity waves and it becomes apparent first in the upper atmosphere and progresses downward. The differences later become more profound on increasingly larger scales, and the growth rates of the differences change in various atmospheric regions and with seasons—corresponding closely with the strength of planetary waves. For example, in December–February the growth rates are largest in the northern and southern mesosphere and lower thermosphere and in the northern stratosphere, while smallest in the southern stratosphere. The growth rates, on the other hand, are not sensitive to the altitude where the small differences are introduced in the initial conditions or the physical nature of the differences. Furthermore, the growth rates in the middle and upper atmosphere are significantly reduced if the lower atmosphere is regularly reinitialized, and the reduction depends on the frequency and the altitude range of the reinitialization.
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Strelnikov, Boris, Martin Eberhart, Martin Friedrich, Jonas Hedin, Mikhail Khaplanov, Gerd Baumgarten, Bifford P. Williams, et al. "Simultaneous in situ measurements of small-scale structures in neutral, plasma, and atomic oxygen densities during the WADIS sounding rocket project." Atmospheric Chemistry and Physics 19, no. 17 (September 11, 2019): 11443–60. http://dx.doi.org/10.5194/acp-19-11443-2019.
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Abstract. In this paper we present an overview of measurements conducted during the WADIS-2 rocket campaign. We investigate the effect of small-scale processes like gravity waves and turbulence on the distribution of atomic oxygen and other species in the mesosphere–lower thermosphere (MLT) region. Our analysis suggests that density fluctuations of atomic oxygen are coupled to fluctuations of other constituents, i.e., plasma and neutrals. Our measurements show that all measured quantities, including winds, densities, and temperatures, reveal signatures of both waves and turbulence. We show observations of gravity wave saturation and breakdown together with simultaneous measurements of generated turbulence. Atomic oxygen inside turbulence layers shows two different spectral behaviors, which might imply a change in its diffusion properties.
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Smith, Ronald B. "100 Years of Progress on Mountain Meteorology Research." Meteorological Monographs 59 (January 1, 2019): 20.1–20.73. http://dx.doi.org/10.1175/amsmonographs-d-18-0022.1.
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ABSTRACT Mountains significantly influence weather and climate on Earth, including disturbed surface winds; altered distribution of precipitation; gravity waves reaching the upper atmosphere; and modified global patterns of storms, fronts, jet streams, and climate. All of these impacts arise because Earth’s mountains penetrate deeply into the atmosphere. This penetration can be quantified by comparing mountain heights to several atmospheric reference heights such as density scale height, water vapor scale height, airflow blocking height, and the height of natural atmospheric layers. The geometry of Earth’s terrain can be analyzed quantitatively using statistical, matrix, and spectral methods. In this review, we summarize how our understanding of orographic effects has progressed over 100 years using the equations for atmospheric dynamics and thermodynamics, numerical modeling, and many clever in situ and remote sensing methods. We explore how mountains disturb the surface winds on our planet, including mountaintop winds, severe downslope winds, barrier jets, gap jets, wakes, thermally generated winds, and cold pools. We consider the variety of physical mechanisms by which mountains modify precipitation patterns in different climate zones. We discuss the vertical propagation of mountain waves through the troposphere into the stratosphere, mesosphere, and thermosphere. Finally, we look at how mountains distort the global-scale westerly winds that circle the poles and how varying ice sheets and mountain uplift and erosion over geologic time may have contributed to climate change.
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Ray, L. C., C. T. S. Lorch, J. O'Donoghue, J. N. Yates, S. V. Badman, C. G. A. Smith, and T. S. Stallard. "Why is the H 3 + hot spot above Jupiter's Great Red Spot so hot?" Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, no. 2154 (August 5, 2019): 20180407. http://dx.doi.org/10.1098/rsta.2018.0407.
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Recent observations of Jupiter's Great Red Spot indicate that the thermosphere above the storm is hotter than its surroundings by more than 700 K. Possible suggested sources for this heating have thus far included atmospheric gravity waves and lightning-driven acoustic waves. Here, we propose that Joule heating, driven by Great Red Spot vorticity penetrating up into the lower stratosphere and coupling to the thermosphere, may contribute to the large observed temperatures. The strength of Joule heating will depend on the local inclination angle of the magnetic field and thus the observed emissions and inferred temperatures should vary with planetary longitude as the Great Red Spot tracks across the planet. This article is part of a discussion meeting issue ‘Advances in hydrogen molecular ions: H 3 + , H 5 + and beyond’.
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Hoffmann, P., and Ch Jacobi. "Planetary wave characteristics of gravity wave modulation from 30–130 km." Advances in Radio Science 10 (September 19, 2012): 271–77. http://dx.doi.org/10.5194/ars-10-271-2012.
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Abstract. Fast gravity waves (GW) have an important impact on the momentum transfer between the middle and upper atmosphere. Experiments with a circulation model indicate a penetration of high phase speed GW into the thermosphere as well as an indirect propagation of planetary waves by the modulation GW of momentum fluxes into the thermosphere. Planetary wave characteristics derived from middle atmosphere SABER temperatures, GW potential energy and ionospheric GPS-TEC data at midlatitudes reveal a possible correspondence of PW signatures in the middle atmosphere and ionosphere in winter around solar maximum (2002–2005). In the case of the westward propagating 16-day wave with zonal wavenumber 1 a possible connection could be found in data analysis (November–December 2003) and model simulation. Accordingly, GW with high phase speeds might play an essential role in the transfer of PW and other meteorological disturbances up to the ionospheric F-region.
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Parihar, N., and A. Taori. "An investigation of long-distance propagation of gravity waves under CAWSES India Phase II Programme." Annales Geophysicae 33, no. 5 (May 18, 2015): 547–60. http://dx.doi.org/10.5194/angeo-33-547-2015.
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Abstract. Coordinated measurements of airglow features from the mesosphere–lower thermosphere (MLT) region were performed at Allahabad (25.5° N, 81.9° E) and Gadanki (13.5° N, 79.2° E), India to study the propagation of gravity waves in 13–27° N latitude range during the period June 2009 to May 2010 under CAWSES (Climate And Weather of Sun Earth System) India Phase II Programme. At Allahabad, imaging observations of OH broadband emissions and OI 557.7 nm emission were made using an all-sky imager, while at Gadanki photometric measurements of OH (6, 2) Meinel band and O2 (0, 1) Atmospheric band emissions were carried out. On many occasions, the nightly observations reveal the presence of similar waves at both locations. Typically, the period of observed similar waves lay in the 2.2–4.5 h range, had large phase speeds (~ 77–331 m s−1) and large wavelengths (~ 1194–2746 km). The images of outgoing long-wave radiation activity of the National Oceanic and Atmospheric Administration (NOAA) and the high-resolution infrared images of KALPANA-1 satellite suggest that such waves possibly originated from some nearby convective sources. An analysis of their propagation characteristics in conjunction with SABER/TIMED temperature profiles and Horizontal Wind Model (HWM 2007) wind estimates suggest that the waves propagated over long distances (~ 1200–2000 km) in atmospheric ducts.
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Miyoshi, Yasunobu, and Hitoshi Fujiwara. "Gravity waves in the equatorial thermosphere and their relation to lower atmospheric variability." Earth, Planets and Space 61, no. 4 (April 2009): 471–78. http://dx.doi.org/10.1186/bf03353164.
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Lin, Cissi Y., Yue Deng, and Aaron Ridley. "Atmospheric Gravity Waves in the Ionosphere and Thermosphere During the 2017 Solar Eclipse." Geophysical Research Letters 45, no. 11 (June 5, 2018): 5246–52. http://dx.doi.org/10.1029/2018gl077388.
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Snively, Jonathan B., Donna A. Calhoun, Pavel A. Inchin, Roberto Sabatini, Christopher J. Heale, and Matthew D. Zettergren. "Modeling of infrasonic and acoustic-gravity wave propagation, nonlinear evolution, and observable effects." Journal of the Acoustical Society of America 152, no. 4 (October 2022): A165. http://dx.doi.org/10.1121/10.0015898.
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Mechanical disturbances associated with hazardous events—e.g., earthquakes, explosions (volcanic or man-made)—and severe weather – generate broad spectra of infrasound and acoustic-gravity waves (AGWs). These wave signals may provide diagnostic insight into the processes that generated them. They are routinely detected as fluctuations in atmospheric pressure, measured at ground or from balloon-borne platforms; at lower frequencies (<1 Hz), and where they may attain sufficient amplitudes at high altitudes, they may also be measured via the fluctuations that they impose in densities of layered species throughout the atmosphere and ionosphere. Thus, they provide complementary remote sensing opportunities, where waves and their effects, especially above and surrounding larger sources, may be diagnosed as they propagate. We review recent progress and techniques for high-fidelity modeling and simulation, to capture the propagation and evolution of low-frequency infrasound and AGWs throughout the atmosphere, from 0–500 km altitude (from surface to exobase). Strategies to (1) efficiently extend model simulation domains well into the diffusive thermosphere, to (2) connect models of atmospheric dynamics to those for other measurable processes (e.g., the ionosphere), and to (3) construct simulations that extend from source processes to specific remote sensing methodologies are discussed.
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Essien, Patrick, Igo Paulino, Cristiano Max Wrasse, Jose Andre V. Campos, Ana Roberta Paulino, Amauri F. Medeiros, Ricardo Arlen Buriti, Hisao Takahashi, Ebenezer Agyei-Yeboah, and Aline N. Lins. "Seasonal characteristics of small- and medium-scale gravity waves in the mesosphere and lower thermosphere over the Brazilian equatorial region." Annales Geophysicae 36, no. 3 (June 21, 2018): 899–914. http://dx.doi.org/10.5194/angeo-36-899-2018.
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Abstract. The present work reports seasonal characteristics of small- and medium-scale gravity waves in the mesosphere and lower thermosphere (MLT) region. All-sky images of the hydroxyl (NIR-OH) airglow emission layer over São João do Cariri (7.4∘ S, 36.5∘ W; hereafter Cariri) were obtained from September 2000 to December 2010, during a total of 1496 nights. For investigation of the characteristics of small-scale gravity waves (SSGWs) and medium-scale gravity waves (MSGWs), we employed the Fourier two-dimensional (2-D) spectrum and keogram fast Fourier transform (FFT) techniques, respectively. From the 11 years of data, we could observe 2343 SSGW and 537 MSGW events. The horizontal wavelengths of the SSGWs were concentrated between 10 and 35 km, while those of the MSGWs ranged from 50 to 200 km. The observed periods for SSGWs were concentrated around 5 to 20 min, whereas the MSGWs ranged from 20 to 60 min. The observed horizontal phase speeds of SSGWs were distributed around 10 to 60 m s−1, and the corresponding MSGWs were around 20 to 120 m s−1. In summer, autumn, and winter both SSGWs and MSGWs propagated preferentially northeastward and southeastward, while in spring the waves propagated in all directions. The critical level theory of atmospheric gravity waves (AGWs) was applied to study the effects of wind filtering on SSGW and MSGW propagation directions. The SSGWs were more susceptible to wind filtering effects than MSGWs. The average of daily mean outgoing longwave radiation (OLR) was also used to investigate the possible wave source region in the troposphere. The results showed that in summer and autumn, deep convective regions were the possible source mechanism of the AGWs. However, in spring and winter the deep convective regions did not play an important role in the waves observed at Cariri, because they were too far away from the observatory. Therefore, we concluded that the horizontal propagation directions of SSGWs and MSGWs show clear seasonal variations based on the influence of the wind filtering process and wave source location. Keywords. Atmospheric composition and structure (airglow and aurora) – electromagnetics (wave propagation) – history of geophysics (atmospheric sciences)
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Wing, Robin, Milena Martic, Colin Triplett, Alain Hauchecorne, Jacques Porteneuve, Philippe Keckhut, Yann Courcoux, Laurent Yung, Patrick Retailleau, and Dorothee Cocuron. "Gravity Wave Breaking Associated with Mesospheric Inversion Layers as Measured by the Ship-Borne BEM Monge Lidar and ICON-MIGHTI." Atmosphere 12, no. 11 (October 22, 2021): 1386. http://dx.doi.org/10.3390/atmos12111386.
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During a recent 2020 campaign, the Rayleigh lidar aboard the Bâtiment d’Essais et de Mesures (BEM) Monge conducted high-resolution temperature measurements of the upper Mesosphere and Lower Thermosphere (MLT). These measurements were used to conduct the first validation of ICON-MIGHTI temperatures by Rayleigh lidar. A double Mesospheric Inversion Layer (MIL) as well as shorter-period gravity waves was observed. Zonal and meridional wind speeds were obtained from locally launched radiosondes and the newly launched ICON satellite as well as from the European Centre for Medium-Range Weather Forecasts (ECMWF-ERA5) reanalysis. These three datasets allowed us to see the evolution of the winds in response to the forcing from the MIL and gravity waves. The wavelet analysis of a case study suggests that the wave energy was dissipated in small, intense, transient instabilities about a given wavenumber in addition to via a broad spectrum of breaking waves. This article will also detail the recent hardware advances of the Monge lidar that have allowed for the measurement of MILs and gravity waves at a resolution of 5 min with an effective vertical resolution of 926 m.
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Garcia, Rolando R., Anne K. Smith, Douglas E. Kinnison, Álvaro de la Cámara, and Damian J. Murphy. "Modification of the Gravity Wave Parameterization in the Whole Atmosphere Community Climate Model: Motivation and Results." Journal of the Atmospheric Sciences 74, no. 1 (January 1, 2017): 275–91. http://dx.doi.org/10.1175/jas-d-16-0104.1.
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Abstract The current standard version of the Whole Atmosphere Community Climate Model (WACCM) simulates Southern Hemisphere winter and spring temperatures that are too cold compared with observations. This “cold-pole bias” leads to unrealistically low ozone column amounts in Antarctic spring. Here, the cold-pole problem is addressed by introducing additional mechanical forcing of the circulation via parameterized gravity waves. Insofar as observational guidance is ambiguous regarding the gravity waves that might be important in the Southern Hemisphere stratosphere, the impact of increasing the forcing by orographic gravity waves was investigated. This reduces the strength of the Antarctic polar vortex in WACCM, bringing it into closer agreement with observations, and accelerates the Brewer–Dobson circulation in the polar stratosphere, which warms the polar cap and improves substantially the simulation of Antarctic temperature. These improvements are achieved without degrading the performance of the model in the Northern Hemisphere stratosphere or in the mesosphere and lower thermosphere of either hemisphere. It is shown, finally, that other approaches that enhance gravity wave forcing can also reduce the cold-pole bias such that careful examination of observational evidence and model performance will be required to establish which gravity wave sources are dominant in the real atmosphere. This is especially important because a “downward control” analysis of these results suggests that the improvement of the cold-pole bias itself is not very sensitive to the details of how gravity wave drag is altered.
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Liu, X., J. Xu, J. Yue, and S. L. Vadas. "Numerical modeling study of the momentum deposition of small amplitude gravity waves in the thermosphere." Annales Geophysicae 31, no. 1 (January 3, 2013): 1–14. http://dx.doi.org/10.5194/angeo-31-1-2013.
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Abstract. We study the momentum deposition in the thermosphere from the dissipation of small amplitude gravity waves (GWs) within a wave packet using a fully nonlinear two-dimensional compressible numerical model. The model solves the nonlinear propagation and dissipation of a GW packet from the stratosphere into the thermosphere with realistic molecular viscosity and thermal diffusivity for various Prandtl numbers. The numerical simulations are performed for GW packets with initial vertical wavelengths (λz) ranging from 5 to 50 km. We show that λz decreases in time as a GW packet dissipates in the thermosphere, in agreement with the ray trace results of Vadas and Fritts (2005) (VF05). We also find good agreement for the peak height of the momentum flux (zdiss) between our simulations and VF05 for GWs with initial λz ≤ 2π H in an isothermal, windless background, where H is the density scale height. We also confirm that zdiss increases with increasing Prandtl number. We include eddy diffusion in the model, and find that the momentum deposition occurs at lower altitudes and has two separate peaks for GW packets with small initial λz. We also simulate GW packets in a non-isothermal atmosphere. The net λz profile is a competition between its decrease from viscosity and its increase from the increasing background temperature. We find that the wave packet disperses more in the non-isothermal atmosphere, and causes changes to the momentum flux and λz spectra at both early and late times for GW packets with initial λz ≥ 10 km. These effects are caused by the increase in T in the thermosphere, and the decrease in T near the mesopause.
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Garcia, Rolando R., Ruth Lieberman, James M. Russell, and Martin G. Mlynczak. "Large-Scale Waves in the Mesosphere and Lower Thermosphere Observed by SABER." Journal of the Atmospheric Sciences 62, no. 12 (December 1, 2005): 4384–99. http://dx.doi.org/10.1175/jas3612.1.
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Abstract Observations made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on board NASA’s Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics (TIMED) satellite have been processed using Salby’s fast Fourier synoptic mapping (FFSM) algorithm. The mapped data provide a first synoptic look at the mean structure and traveling waves of the mesosphere and lower thermosphere (MLT) since the launch of the TIMED satellite in December 2001. The results show the presence of various wave modes in the MLT, which reach largest amplitude above the mesopause and include Kelvin and Rossby–gravity waves, eastward-propagating diurnal oscillations (“non-sun-synchronous tides”), and a set of quasi-normal modes associated with the so-called 2-day wave. The latter exhibits marked seasonal variability, attaining large amplitudes during the solstices and all but disappearing at the equinoxes. SABER data also show a strong quasi-stationary Rossby wave signal throughout the middle atmosphere of the winter hemisphere; the signal extends into the Tropics and even into the summer hemisphere in the MLT, suggesting ducting by westerly background zonal winds. At certain times of the year, the 5-day Rossby normal mode and the 4-day wave associated with instability of the polar night jet are also prominent in SABER data.
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Hickey, M. P., and K. D. Cole. "A quartic dispersion equation for internal gravity waves in the thermosphere." Journal of Atmospheric and Terrestrial Physics 49, no. 9 (September 1987): 889–99. http://dx.doi.org/10.1016/0021-9169(87)90003-1.
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Miyahara, S., and J. M. Forbes. "Interactions between diurnal tides and gravity waves in the lower thermosphere." Journal of Atmospheric and Terrestrial Physics 56, no. 10 (August 1994): 1365–73. http://dx.doi.org/10.1016/0021-9169(94)90074-4.
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Oyama, S., and B. J. Watkins. "Generation of Atmospheric Gravity Waves in the Polar Thermosphere in Response to Auroral Activity." Space Science Reviews 168, no. 1-4 (November 12, 2011): 463–73. http://dx.doi.org/10.1007/s11214-011-9847-z.
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Williams, B. P., D. C. Fritts, C. Y. She, and R. A. Goldberg. "Gravity wave propagation through a large semidiurnal tide and instabilities in the mesosphere and lower thermosphere during the winter 2003 MaCWAVE rocket campaign." Annales Geophysicae 24, no. 4 (July 3, 2006): 1199–208. http://dx.doi.org/10.5194/angeo-24-1199-2006.
Повний текст джерелаАнотація:
Abstract. The winter MaCWAVE (Mountain and convective waves ascending vertically) rocket campaign took place in January 2003 at Esrange, Sweden and the ALOMAR observatory in Andenes, Norway. The campaign combined balloon, lidar, radar, and rocket measurements to produce full temperature and wind profiles from the ground to 105 km. This paper will investigate gravity wave propagation in the mesosphere and lower thermosphere using data from the Weber sodium lidar on 28–29 January 2003. A very large semidiurnal tide was present in the zonal wind above 80 km that grew to a 90 m/s amplitude at 100 km. The superposition of smaller-scale gravity waves and the tide caused small regions of possible convective or shear instabilities to form along the downward progressing phase fronts of the tide. The gravity waves had periods ranging from the Nyquist period of 30 min up to 4 h, vertical wavelengths ranging from 7 km to more than 20 km, and the frequency spectra had the expected –5/3 slope. The dominant gravity waves had long vertical wavelengths and experienced rapid downward phase progression. The gravity wave variance grew exponentially with height up from 86 to 94 km, consistent with the measured scale height, suggesting that the waves were not dissipated strongly by the tidal gradients and resulting unstable regions in this altitude range.
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Essien, Patrick, Cosme Alexandre Oliveira Barros Figueiredo, Hisao Takahashi, Cristiano Max Wrasse, Diego Barros, Nana Ama Browne Klutse, Solomon Otoo Lomotey, Toyese Tunde Ayorinde, Delano Gobbi, and Anderson V. Bilibio. "Long-Term Study on Medium-Scale Traveling Ionospheric Disturbances Observed over the South American Equatorial Region." Atmosphere 12, no. 11 (October 26, 2021): 1409. http://dx.doi.org/10.3390/atmos12111409.
Повний текст джерелаАнотація:
Using data collected by the GNSS dual-frequency receivers network, de-trended TEC maps were generated to identify and characterize the medium-scale traveling ionospheric disturbances (MSTIDs) over the South American equatorial region (latitude: 0∘ to 15∘ S and longitude: 30∘ to 55∘ W) during solar cycle 24 (from January 2014 to December 2019). A total of 712 MSTIDs were observed during quiet geomagnetic conditions. The Frequency of occurrence of MSTID is high during the solar maximum and low in the minimum phase. This might be due to the solar cycle dependence of gravity wave activity in the lower atmosphere and gravity wave propagation conditions in the thermosphere. The predominant daytime MSTIDs, representing 80% of the total observations, occurred in winter (June-August season in the southern hemisphere) with the secondary peak in the equinox; while the evening time MSTIDs, representing 18% of the entire events, occurred in summer (December to February season) and equinox (March to May and September to November), and the remaining 2% of the MSTIDs were observed during nighttime. The seasonal variation of the MSTID events was attributed to the source mechanisms generating them, the wind filtering and dissipation effects, and the local time dependency. The horizontal wavelengths of the MSTIDs were mostly concentrated between 500 and 800 km, with the mean value of 667 ± 131 km. The observed periods ranged from 30 to 45 min with the mean value of 36 ± 7 min. The observed horizontal phase speeds were distributed around 200 to 400 m/s, with the corresponding mean of 301 ± 75 m/s. The MSTIDs in the winter solstice and equinoctial months preferentially propagated northeastward and northwestward. Meanwhile, during the summer solstice, they propagated in all directions. The anisotropy of the propagation direction might be due to several reasons: the wind and dissipative filtering effects, ion drag effects, the primary source region, and the presence of the secondary or tertiary gravity waves in the thermosphere. Atmospheric gravity waves from strong convective sources might be the primary precursor for the observed equatorial MSTIDs. In all seasons, we noted that the MSTIDs propagating southeastward were probably excited by the likely gravity waves generated by the intertropical convergence zone (ITCZ).
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Vadas, Sharon L. "Horizontal and vertical propagation and dissipation of gravity waves in the thermosphere from lower atmospheric and thermospheric sources." Journal of Geophysical Research: Space Physics 112, A6 (June 2007): n/a. http://dx.doi.org/10.1029/2006ja011845.
Повний текст джерела
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Ashkaliev, Ya F., G. I. Gordienko, Ch Jacobi, Yu G. Litvinov, V. V. Vodyannikov, and A. F. Yakovets. "Comparison of travelling ionospheric disturbance measurements with thermosphere/ionosphere model results." Annales Geophysicae 21, no. 4 (April 30, 2003): 1031–37. http://dx.doi.org/10.5194/angeo-21-1031-2003.
Повний текст джерелаАнотація:
Abstract. Comparisons of modeled and measured responses of the ionosphere to the passage of atmospheric gravity waves are made for data recorded by an ionosonde located at Almaty (76°55' E, 43°15' N) from June 2000 until May 2001. Temporal variations of the altitude (hmF) and electron content (NmF) of the F-layer peak are used for comparisons. A significant part of the observations showed well-defined wave structures on the hmF, NmF and other parameter variations observed throughout the entire nights. Both the modeling study and measurements showed that, as the F-layer is lifted by the positive surge in gravity wave, the electron content at the F-layer peak decreases, with the slab thickness being increased as well. Subsequently, the opposite happens as hmF falls below its equilibrium value. Some discrepancy between the model and experimental results related to the phase difference between hmF and NmF variations is revealed.Key words. Ionosphere (ionosphere-atmosphere interaction, ionospheric disturbances)
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Mixa, Tyler, Andreas Dörnbrack, and Markus Rapp. "Nonlinear Simulations of Gravity Wave Tunneling and Breaking over Auckland Island." Journal of the Atmospheric Sciences 78, no. 5 (May 2021): 1567–82. http://dx.doi.org/10.1175/jas-d-20-0230.1.
Повний текст джерелаАнотація:
AbstractHorizontally dispersing gravity waves with horizontal wavelengths of 30–40 km were observed at mesospheric altitudes over Auckland Island by the airborne advanced mesospheric temperature mapper during a Deep Propagating Gravity Wave Experiment (DEEPWAVE) research flight on 14 July 2014. A 3D nonlinear compressible model is used to determine which propagation conditions enabled gravity wave penetration into the mesosphere and how the resulting instability characteristics led to widespread momentum deposition. Results indicate that linear tunneling through the polar night jet enabled quick gravity wave propagation from the surface up to the mesopause, while subsequent instability processes reveal large rolls that formed in the negative shear above the jet maximum and led to significant momentum deposition as they descended. This study suggests that gravity wave tunneling is a viable source for this case and other deep propagation events reaching the mesosphere and lower thermosphere.
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Chun, Hye-Yeong, Hyun-Joo Choi, and In-Sun Song. "Effects of Nonlinearity on Convectively Forced Internal Gravity Waves: Application to a Gravity Wave Drag Parameterization." Journal of the Atmospheric Sciences 65, no. 2 (February 1, 2008): 557–75. http://dx.doi.org/10.1175/2007jas2255.1.
Повний текст джерелаАнотація:
Abstract In the present study, the authors propose a way to include a nonlinear forcing effect on the momentum flux spectrum of convectively forced internal gravity waves using a nondimensional numerical model (NDM) in a two-dimensional framework. In NDM, the nonlinear forcing is represented by nonlinear advection terms multiplied by the nonlinearity factor (NF) of the thermally induced internal gravity waves for a given specified diabatic forcing. It was found that the magnitudes of the waves and resultant momentum flux above the specified forcing decrease with increasing NF due to cancellation between the two forcing mechanisms. Using the momentum flux spectrum obtained by the NDM simulations with various NFs, a scale factor for the momentum flux, normalized by the momentum flux induced by diabatic forcing alone, is formulated as a function of NF. Inclusion of the nonlinear forcing effect into current convective gravity wave drag (GWD) parameterizations, which consider diabatic forcing alone by multiplying the cloud-top momentum flux spectrum by the scale factor, is proposed. An updated convective GWD parameterization using the scale factor is implemented into the NCAR Whole Atmosphere Community Climate Model (WACCM). The 10-yr simulation results, compared with those by the original convective GWD parameterization considering diabatic forcing alone, showed that the magnitude of the zonal-mean cloud-top momentum flux is reduced for wide range of phase speed spectrum by about 10%, except in the middle latitude storm-track regions where the cloud-top momentum flux is amplified. The zonal drag forcing is determined largely by the wave propagation condition under the reduced magnitude of the cloud-top momentum flux, and its magnitude decreases in many regions, but there are several areas of increasing drag forcing, especially in the tropical upper mesosphere and lower thermosphere.
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Yang, F., M. E. Schlesinger, E. V. Rozanov, N. Andronova, V. A. Zubov, and L. B. Callis. "Sensitivity of middle atmospheric temperature and circulation in the UIUC GCM to the treatment of subgrid-scale gravity-wave breaking." Atmospheric Chemistry and Physics Discussions 6, no. 5 (September 25, 2006): 9085–121. http://dx.doi.org/10.5194/acpd-6-9085-2006.
Повний текст джерелаАнотація:
Abstract. The sensitivity of the middle atmospheric temperature and circulation to the treatment of mean-flow forcing due to breaking gravity waves at the sub-grid scale was investigated using the University of Illinois at Urbana-Champaign 40-layer General Circulation Model (GCM). The gravity-wave forcing was represented either by Rayleigh friction or by a detailed parameterization scheme with different sets of parameters. The modeled middle atmospheric temperature and circulation exhibit large sensitivity to the parameterized sub-grid gravity-wave forcing. A large warm bias of up to 50°C was found in the model's summer upper mesosphere and lower thermosphere. This warm bias was caused by the inability of the GCM to simulate the reversal of the zonal winds from easterly to westerly crossing the mesopause in the summer hemisphere. Attempts were made to slow down the easterly winds near the mesopause and to reduce the warm bias. The GCM was able to realistically simulate the semi-annual oscillation in the upper stratosphere and lower mesosphere with observational constraints on certain parameter values, but failed to simulate the quasi-biennial oscillation in any of the experiments. Budget analysis indicates that in the middle atmosphere the forces that act to maintain a steady zonal-mean zonal wind are primarily those associated with the meridional transport circulation and breaking gravity waves. Contributions from the interaction of the model-resolved eddies with the mean flow are secondary.