Modulation of Low‐Altitude Ionospheric Upflow by Linear and Nonlinear Atmospheric Gravity Waves
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M. R. Burleigh↗
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Gravity waves in a realistic atmosphere.
Internal atmospheric gravity waves in isothermal medium, solving hydrodynamic equations, determining wave propagation in realistic atmosphere for range of wave parameters, wind amplitude, reflected energy, etc
WIND CIRCULATION↗
Mars Climate Sounder Observations of Gravity Wave Activity throughout Mars’s Lower Atmosphere
Gravity waves are one way Mars’s lower atmospheric weather can affect the circulation and even composition of Mars’s middle and upper atmosphere. A recent study showed how on-planet observations near the center of the 15 micron CO2band by the A3 channel(635–665 cm−1)of the Mars Climate Sounder on board Mars Reconnaissance Orbiter (MRO-MCS) could sense horizontally short, vertically broad gravity waves at≈25 km above the surface by looking at small-scale radiance variability in temperature-sensitive channels. This approach is extended here to two additional channels closer to the wings of the 15 micron CO2band,A1 (595–615 cm−1) and A2 (615–645 cm−1), to sense gravity waves throughout the lower atmosphere. Using information from all three channels demonstrates that gravity wave activity in Mars’s lowermost atmosphere is dominated by orographic sources, particularly over the extremely rough terrain of Valles Marineris. Much of this orographic population is either trapped or filtered in the lowest two scale heights, such that variations in filtering and non-orographic sources shape the gravity wave population observed at 25 km above the surface. During global dust storms, however, gravity wave activity in the first scale height decreases by approximately a factor of two, yet trapping/filtering of what activity remains in the tropics substantially weakens. Exceptionally high radiance variability at night in the tropics during the less dusty part of the year is the result of observing mesospheric clouds rather than gravity waves.
Nicholas G Heavens↗
La Soufriere Volcanic Eruptions Launched Gravity Waves Into Space
Atmospheric gravity waves can be excited by explosive volcanic eruptions and may reach Earth's upper atmosphere. In this study, we report on mesoscale concentric gravity waves observed in the mesopause airglow layer following the La Soufriere volcano eruption in April 2021. A large ash plume observed by the spaceborne Multi-angle Imaging SpectroRadiometer instrument on April 10 reached ∼20 km. Temporal evolution of the volcanic ash plume was provided by the GOES-16 Advanced Baseline Imager. Nightglow gravity waves were observed by the Visible Infrared Imaging Radiometer Suite Day Night Band. These waves had horizontal wavelengths of ∼25–40 km, and took about a half-to-1 hr to travel from the tropopause to the mesopause. Some concentric ionospheric disturbance signatures are also seen in Global Navigation Satellite System-total electron content maps. We found the launch of gravity waves to be highly correlated with the elevated ash plume from explosive eruptions.
gravity waves↗
A ray tracing model of gravity wave propagation and breakdown in the middle atmosphere
Gravity wave ray tracing and wave packet theory is used to parameterize wave breaking in the mesosphere. Rays are tracked by solving the group velocity equations, and the interaction with the basic state is determined by considering the evolution of the packet wave action density. The ray tracing approach has a number of advantages over the steady state parameterization as the effects of gravity wave focussing and refraction, local dissipation, and wave response to rapid changes in the mean flow are more realistically considered; however, if steady state conditions prevail, the method gives identical results. The ray tracing algorithm is tested using both interactive and noninteractive models of the basic state. In the interactive model, gravity wave interaction with the polar night jet on a beta-plane is considered. The algorithm produces realistic polar night jet closure for weak topographic forcing of gravity waves. Planetary scale waves forced by local transfer of wave action into the basic flow in turn transfer their wave action into the zonal mean flow. Highly refracted rays are also found not to contribute greatly to the climatology of the mesosphere, as their wave action is severely reduced by dissipation during their lateral travel.
Schoeberl, M. R.↗
Gravity Waves
Atmospheric parameters fluctuate on all scales. In the mesoscale these fluctuations are occasionally sinusoidal so that they can be interpreted as gravity waves. Usually, however, the fluctuations are noise like, so that their cause is not immediately evident. Results of mesoscale observations in the 20 to 120 m altitude range that are suitable for incorporation into a model atmosphere are very limited. In the stratosphere and lower mesosphere observations are sparse and very little data has been summarized into appropriate form. There is much more data in the upper mesosphere and lower thermosphere, but again very little of it has been summarized. The available mesoscale spectra of horizontal wind u versus vertical wave number m in the 20 to 120 km altitude range are shown together with a spectrum from the lower atmosphere for comparison. Further information about these spectra is given. In spite of the large range of altitudes and latitudes, the spectra from the lower atmosphere (NASA, 1971 and DEWAN, 1984) are remarkably similar in both shape and amplitude. The mean slopes of -2.38 for the NASA spectrum and -2.7 for the Dewan spectra are supported by the mean slope of -2.75 found by ROSENBERG et al. (1974). The mesospheric spectrum is too short to establish a shape. Its amplitude is about an order of magnitude larger than the NASA spectrum in the same wave number range. The NASA and Dewan spectra suggest that the mesoscale spectra in the lower atmosphere are insensitive to meteorological conditions.
Vanzandt, T. E.↗
Ionospsheric observation of enhanced convection-initiated gravity waves during tornadic storms
Atmospheric gravity waves associated with tornadoes, with locally severe storms occuring with tornadoes, and with hurricanes were studied through the coupling between the ionosphere and the troposphere. Reverse group ray tracing computations of gravity waves observed by an ionospheric Doppler sounder array were analyzed. The results of ray tracing computations and comparisons between the computed location of the wave sources and with conventional meteorological data indicate that the computed sources of the waves were near the touchdown of the tornadoes, near the eye of the hurricanes, and directly on the squall line of the severe thunderstorms. The signals excited occurred one hour in advance of the tornadoes and three hours in advance of the hurricanes. Satellite photographs show convective overshooting turrets occurring at the same locations and times the gravity waves were being excited. It is suggested that gravity wave observations, conventional meteorological data, and satellite photographs be combined to develop a remote sensing technique for detecting severe storms.
Hung, R. J.↗
Propagation of internal gravity waves in a thermally stratified atmosphere.
Internal gravity wave propagation in thermally stratified atmosphere
GRAVITY WAVE↗
Generation of turbulence in the upper atmosphere by internal gravity waves.
Turbulence in upper atmosphere possibly due to density fluctuations accompanying internal gravity waves
CONVECTION CURRENT↗
Facilitating Heliophysics Research by the Virtual Wave Observatory (VWO) Context Data Search Capability
Wave phenomena, ranging from freely propagating electromagnetic radiation (e.g., solar radio bursts, AKR) to plasma wave modes trapped in various plasma regimes (e.g., whistlers, Langmuir and ULF waves) and atmospheric gravity waves, are ubiquitous in the heliosphere. Because waves can propagate, wave data obtained at a given observing location may pertain to wave oscillations generated locally or from afar. While wave data analysis requires knowledge of wave characteristics specific to different wave modes, the search for appropriate data for heliophysics wave studies also requires knowledge of wave phenomena. In addition to deciding whether the interested wave activity is electrostatic (i.e., locally trapped) or electromagnetic (with propagation over distances), considerations must be given to the dependence of the wave activity on observer's location or viewing geometry, propagating frequency range and whether the wave data were acquired by passive or active observations. Occurances of natural wave emissions i the magnetosphere (e.g, auroral kilometric radiation) are often dependent also on the state (e.e., context) of the magnetosphere that varies with the changing solar wind, IMF and geomagnetic conditions. Fung and Shao [2008] showed recently that magnetospheric state can be specified by a set of suitably time-shifted solar wind, IMF and the multi-scale geomagnetic response parameters. These parameters form a magnetospheric state vector that provides the basis for searching magnetospheric wave data by their context conditions. Using the IMAGE Radio Plasma Imager (RPI) data and the NASA Magnetospheric State Query System (MSOS) [Fung, 2004], this presentation demonstrates the VWO context data search capability under development and solicits feedback from the Heliophysics research community for improvements.
Fung, Shing F.↗
Atmospheric waves and the ionosphere.
A review of evidence supporting the existence of atmospheric waves is presented, and a simple, theoretical approach for describing them is shown. Suggestions for gravity wave sources include equatorial and auroral electrojet, auroral and polar substorm heating, atmospheric jet streams, and large oceanic tides. There are reviewed previous studies dealing with the interaction between ionization and atmospheric waves believed to exist at ionospheric heights. These waves include acoustic waves, evanescent waves, and internal atmospheric gravity waves. It is explained that mode analysis, often employed when an increased number of layers is used for a more complete profile, is inapplicable for waves very close to a source.
Beer, T.↗
Internal gravity wave-atmospheric wind interaction - A cause of clear air turbulence.
The interaction between an internal gravity wave (IGW) and a vertical wind shear is discussed as a possible cause in the production of clear air turbulence in the free atmosphere. It is shown that under certain typical condition the interaction of an IGW with a background wind shear near a critical level provides a mechanism for depositing sufficient momentum in certain regions of the atmosphere to significantly increase the local mean wind shear and to lead to the production of turbulence.
Bekofske, K.↗
Group rays of internal gravity waves in a wind- stratified atmosphere
Internal gravity wave propagation in neutral wind stratified atmospheric model
Cowling, D. H.↗
Acoustic-gravity Waves in the Earth's Atmosphere. I - the General Nature of Acoustic-gravity Waves. II - Acoustic- Gravity Wave Ducting in the Atmosphere by Vertical Temperature Structure
Nature, propagation, and ducting of acoustic gravity waves in earths atmosphere
WAVE PROPAGATION↗
A simple nearly analytic model of a gravity wave driven middle atmospheric circulation
A nearby analytic model of a gravity wave driven middle atmosphere circulation is formulated. The simplified model represents the one-dimensional interaction of a single gravity wave mode with a zonal-mean flow. Solutions of this model are shown to agree very well with numerical results from a more complete mean-flow/gravity-wave model (essentially the model developed by Holton, 1982). A single nondimensional parameter, the ratio of a mean flow radiative forcing parameter, and the gravity wave momentum flux incident into the middle atmosphere from below largely determine the solution of the model. For typical middle atmosphere parameter values, an approximate solution can be obtained, and this solution permits the parameter dependence of the circulation to be characterized very simply. The gravity wave driven circulation extends downward from the level (the breaking level, approximately) where the momentum flux equals the mean flow radiative forcing.
Barnes, Jeffrey R.↗
Dynamical heating of the upper atmosphere.
Ionospheric heating by upward propagating internal atmospheric gravity waves
ATMOSPHERIC HEAT BUDGET↗
Estimation of neutral wind velocity in the ionospheric heights by HF-Doppler technique
Three net stations located about 100 kilometers apart were set up around the station of the standard frequency and time signals (JJY) in central Japan and measurements of atmospheric gravity waves in the ionospheric heights (F-region, 200 to 400 km) were made by means of the HF-Doppler technique during the period of February 1983 to December 1983. The frequencies of the signals received are 5.0, 8.0 and 10.0 MHz, but only the 8.0 MHz signals are used for the present study, because no ambiguities due to the interference among other stations such as BPM, BSF, etc. exist by the use of 8.0 MHz. Two main results concerning the horizontal phase velocity of the atmospheric gravity waves with periods of 40 to 70 min may be summarized as follows: (1) the value of the phase velocity ranges from 50 m/s to 300 m/s; (2) the direction of the gravity wave propagation shows a definite seasonal variation. The prevailing direction of the gravity waves in winter is from north to south, which is consistent with the results obtained from other investigations. On the other hand, the two directions, from northeast to southwest and from southeast to northeast, dominate in summer.
Kitamura, T.↗
The Influence of Tropospheric Processes in Modeling the Middle Atmosphere with Gravity Waves
Our Numerical Spectral Model (NSM) extends from the ground up into the thermosphere and has a vertical grid point resolution of about 0.5 km to resolve the interactions of gravity waves (GWs) described with Hines' Doppler Spread Parameterization (DSP). This model produces in the stratosphere and mesosphere the major features of QBO, SAO, tides, and planetary waves. The purpose of this paper is to discuss results from an initial study with our 3D model that shows how certain tropospheric processes can affect the dynamics of the middle atmosphere. Under the influence of tropospheric heating, and augmented by GW interactions, two distinct but related processes can be identified. (1) A meridional circulation develops in the stratosphere, with rising motions at low latitudes that are in magnitude comparable to the downward propagation of the QBO. As Dunkerton pointed out, a larger GW source is then required to reproduce the observed QBO, which tends to move us closer to the values recommended for the DSP. This has significant consequences for our model results that describe the upper mesosphere, considering the general importance of GWs for this region and in influencing planetary waves (e.g., 2-day wave) and tides in particular. (2) Tropospheric heating produces zonal jets near the tropopause that are related to latitudinal variations in pressure and reversing temperature variations (resembling the dynamical conditions near the mesopause), which in turn is conducive to generate baroclinic instability. Modeling results show that our ability to generate the QBO critically depends on the magnitude of the temperature reversal that is a measure of this instability. Planetary waves are generated in this process, which can apparently interfere with or augment the GW interactions. As originally demonstrated by Lindzen and Holton, the eastward propagating Kelvin waves and westward propagating Rossby gravity waves (generated by tropospheric convection) can in principle provide the acceleration to influence the QBO, and we were able to confirm this with our 3D model.
Mayr, H. G.↗