Waves at the edge of space revealed by noctilucent cloud observations using camera and lidar

2021 ◽  
Author(s):  
Gerd Baumgarten ◽  
J. Federico Conte ◽  
Jens Fiedler ◽  
Michael Gerding ◽  
Franz-Josef Lübken
Keyword(s):  
Gravity Waves ◽  
Radiative Forcing ◽  
Transition To Turbulence ◽  
Small Scale ◽  
High Time Resolution ◽  
Noctilucent Cloud ◽  
Mesopause Region ◽  
Acoustic Gravity Waves ◽  
Global Circulation ◽  
Small Scale Structures

<p>Noctilucent clouds (NLC) exist at an altitude of about 83 km during the summer season at middle and polar latitudes. They consist of icy particles that exist in the polar summer mesopause region where the atmosphere is about 100 K colder than expected from pure radiative forcing. Dynamical effects, for example the dissipation of gravity waves, play an important role in the global circulation finally leading to the cold summer mesopause region. Ever since the first reports on the occurrence of NLC in 1885 the observers noticed distinct structures in the clouds that are most often wave-like. However at times the wave field becomes seemingly chaotic. <br><br>State of the art lidar and camera observations of NLC allow studying small-scale structures of tens of meters in the vertical and horizontal direction. Given a high time resolution (about one second), the development of these structures is measured on temporal scales spanning the range from inertia gravity waves to acoustic gravity waves. We will show observations with the RMR-lidars at ALOMAR (Northern Norway at 69°N) and Kühlungsborn (54°N) as well as cameras located nearby these stations. Using these combined observations we study waves and their transition to turbulence.</p>

scholarly journals Simultaneous in situ measurements of small-scale structures in neutral, plasma, and atomic oxygen densities during WADIS sounding rocket project

2019 ◽  
Author(s):  
Boris Strelnikov ◽  
Martin Eberhart ◽  
Martin Friedrich ◽  
Jonas Hedin ◽  
Mikhail Khaplanov ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Atomic Oxygen ◽  
Density Fluctuations ◽  
Sounding Rocket ◽  
Small Scale ◽  
Scale Structures ◽  
Small Scale Structures ◽  
Mlt Region ◽  
Diffusion Properties

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 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 change of its diffusion properties.

Numerical Modeling of Nonlinear Interactions of Spectral Components of Acoustic-Gravity Waves in the Middle and Upper Atmosphere

2020 ◽  
Author(s):  
Nikolai M. Gavrilov ◽  
Sergej P. Kshevetskii
Keyword(s):  
Gravity Waves ◽  
Upper Atmosphere ◽  
Jet Flows ◽  
Small Scale ◽  
Nonlinear Interactions ◽  
Mean Flow ◽  
Wave Source ◽  
Acoustic Gravity Waves ◽  
The Mean ◽  
Wave Modes

<p>Acoustic-gravity waves (AGWs) measuring at big heights may be generated in the troposphere and propagate upwards. A high-resolution three-dimensional numerical model was developed for simulating nonlinear AGWs propagating from the ground to the upper atmosphere. The model algorithms are based on the finite-difference analogues of the main conservation laws. This methodology let us obtaining the physically correct generalized wave solutions of the nonlinear equations. Horizontally moving sinusoidal structures of vertical velocity on the ground are used for the AGW excitation in the model. Numerical simulations were made in an atmospheric region having horizontal dimensions up to several thousand kilometers and the height extention up to 500 km. Vertical distributions of the mean temperature, density, molecular viscosity and thermal conductivity are specified using standard models of the atmosphere.</p><p>Simulations were made for different horizontal wavelengths, amplitudes and speeds of the wave sources at the ground. After “switch on” the tropospheric wave source, an initial AGW pulse very quickly (for several minutes) could propagate to heights up to 100 km and above. AGW amplitudes increase with height and waves may break down in the middle and upper atmosphere. Wave instability and dissipation may lead to formations of wave accelerations of the mean flow and to producing wave-induced jet flows in the middle and upper atmosphere. Nonlinear interactions may lead to instabilities of the initial wave and to the creation of smaller-scale perturbations. These perturbations may increase temperature and wind gradients and could enhance the wave energy dissipation.</p><p>In this study, the wave sources contain a superposition of two AGW modes with different periods, wavelengths and phase speeds. Longer-period AGW modes served as the background conditions for the shorter-period wave modes. Thus, the larger-scale AGWs can modulate amplitudes of small-scale waves. In particular, interactions of two wave modes could sharp vertical temperature gradients and make easier the wave breaking and generating  turbulence. On the other hand, small-wave wave modes might increase dissipation and modify the larger-scale modes.This study was partially supported by the Russian Basic Research Foundation (# 17-05-00458).</p>

Small scale structures of NLC observed by lidar at 69°N/69°S and their possible relation to gravity waves

2013 ◽  
Vol 104 ◽  
pp. 244-252 ◽  
Author(s):  
N. Kaifler ◽  
G. Baumgarten ◽  
A.R. Klekociuk ◽  
S.P. Alexander ◽  
J. Fiedler ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Small Scale ◽  
Scale Structures ◽  
Small Scale Structures

Gravity wave emission in an atmosphere-like configuration of the differentially heated rotating annulus experiment

2014 ◽  
Vol 758 ◽  
pp. 287-311 ◽  
Author(s):  
Sebastian Borchert ◽  
Ulrich Achatz ◽  
Mark D. Fruman
Keyword(s):  
Gravity Waves ◽  
Outer Cylinder ◽  
Small Scale ◽  
Cylinder Wall ◽  
Baroclinic Wave ◽  
Azimuthal Mode ◽  
Dimensional Version ◽  
Scale Structures ◽  
Wave Emission ◽  
Small Scale Structures

AbstractA finite-volume model of the classic differentially heated rotating annulus experiment is used to study the spontaneous emission of gravity waves (GWs) from jet stream imbalances, which may be an important source of these waves in the atmosphere and for which no satisfactory parameterisation exists. Experiments were performed using a classic laboratory configuration as well as using a much wider and shallower annulus with a much larger temperature difference between the inner and outer cylinder walls. The latter configuration is more atmosphere-like, in particular since the Brunt–Väisälä frequency is larger than the inertial frequency, resulting in more realistic GW dispersion properties. In both experiments, the model is initialised with a baroclinically unstable axisymmetric state established using a two-dimensional version of the code, and a low-azimuthal-mode baroclinic wave featuring a meandering jet is allowed to develop. Possible regions of GW activity are identified by the horizontal velocity divergence and a modal decomposition of the small-scale structures of the flow. Results indicate GW activity in both annulus configurations close to the inner cylinder wall and within the baroclinic wave. The former is attributable to boundary layer instabilities, while the latter possibly originates in part from spontaneous GW emission from the baroclinic wave.

scholarly journals Identification of linear slow sausage waves in magnetic pores

2007 ◽  
Vol 3 (S247) ◽  
pp. 351-354 ◽  
Author(s):  
I. Dorotovič ◽  
R. Erdélyi ◽  
V. Karlovský
Keyword(s):  
Magnetic Field ◽  
Gravity Waves ◽  
Morphological Changes ◽  
Average Rate ◽  
Linear Trend ◽  
Solar Interior ◽  
Small Scale ◽  
Temporal Area ◽  
Acoustic Gravity Waves ◽  
The Magnetic Field

AbstractThe analysis of an 11-hour series of high resolution white light observations of a large pore in the sunspot group NOAA 7519, observed on 5 June 1993 with the Swedish Vacuum Solar Telescope at La Palma on Canary Islands, has been recently described by Dorotovičet al. (2002). Special attention was paid to the evolution of a filamentary region attached to the pore, to horizontal motions around the pore, and to small-scale morphological changes. One of the results, relevant to out work here, was the determination of temporal area evolution of the studied pore where the area itself showed a linear trend of decrease with time at an average rate of −0.23 Mm2h−1during the entire observing period. Analysing the time series of the are of the pore, there is strong evidence that coupling between the solar interior and magnetic atmosphere can occur at various scales and that the referred decrease of the area may be connected with a decrease of the magnetic field strength according to the magnetic field-to-size relation. Periods of global acoustic, e.g.p-mode, driven waves are usually in the range of 5–10 minutes, and are favourite candidates for the coupling of interior oscillations with atmospheric dynamics. However, by assuming that magneto-acoustic gravity waves may be there too, and may act as drivers, the observed periodicities (frequencies) are expected to be much longer (smaller), falling well within the mMHz domain. In this work we determine typical periods of such range in the area evolution of the pore using wavelet analysis. The resulted periods are in the range of 20–70 minutes, suggesting that periodic elements of the temporal evolution of the area of this studied pore could be linked to, and considered as, observational evidence of linear low-frequency slow sausage (magneto-acoustic gravity) waves in magnetic pores. This would give us further evidence on the coupling of global solar oscillations to the overlaying magnetic atmosphere.

scholarly journals Analysis and modeling of ducted and evanescent gravity waves observed in the Hawaiian airglow

2009 ◽  
Vol 27 (8) ◽  
pp. 3213-3224 ◽  
Author(s):  
D. B. Simkhada ◽  
J. B. Snively ◽  
M. J. Taylor ◽  
S. J. Franke
Keyword(s):  
Gravity Waves ◽  
Wave Structure ◽  
Small Scale ◽  
Wind Flow ◽  
Strong Wind ◽  
Mesopause Region ◽  
Opposite Case ◽  
Local Propagation ◽  
First Case ◽  
Short Period

Abstract. Short-period gravity waves of especially-small horizontal scale have been observed in the Maui, Hawaii airglow. Typical small-scale gravity wave events have been investigated, and intrinsic wave propagation characteristics have been calculated from simultaneous meteor radar wind measurements. Here we report specific cases where wave structure is significantly determined by the local wind structure, and where wave characteristics are consistent with ducted or evanescent waves throughout the mesopause region. Two of the documented events, exhibiting similar airglow signatures but dramatically different propagation conditions, are selected for simple numerical modeling case studies. First, a Doppler-ducted wave trapped within relatively weak wind flow is examined. Model results confirm that the wave is propagating in the 85–95 km region, trapped weakly by evanescence above and below. Second, an evanescent wave in strong wind flow is examined. Model results suggest an opposite case from the first case study, where the wave is instead trapped above or below the mesopause region, with strong evanescence arising in the 85–95 km airglow region. Distinct differences between the characteristics of these visibly-similar wave events demonstrate the need for simultaneous observations of mesopause winds to properly assess local propagation conditions.

scholarly journals Characteristics of equatorial gravity waves derived from mesospheric airglow imaging observations

2009 ◽  
Vol 27 (4) ◽  
pp. 1625-1629 ◽  
Author(s):  
S. Suzuki ◽  
K. Shiokawa ◽  
A. Z. Liu ◽  
Y. Otsuka ◽  
T. Ogawa ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Power Spectra ◽  
Small Scale ◽  
Two Dimensional ◽  
Quasi Biennial Oscillation ◽  
Mesopause Region ◽  
The Waves ◽  
Biennial Oscillation

Abstract. We present the characteristics of small-scale (<100 km) gravity waves in the equatorial mesopause region derived from OH airglow imaging observations at Kototabang (100.3° E, 0.2° S), Indonesia, from 2002 to 2005. We adopted a method that could automatically detect gravity waves in the airglow images using two-dimensional cross power spectra of gravity waves. The propagation directions of the waves were likely controlled by zonal filtering due to stratospheric mean winds that show a quasi-biennial oscillation (QBO) and the presence of many wave sources in the troposphere.

scholarly journals The research on small-scale structures of ice particle density and electron density in the mesopause region

2019 ◽  
Author(s):  
Ruihuan Tian ◽  
Jian Wu ◽  
Jinxiu Ma ◽  
Yonggan Liang ◽  
Hui Li ◽  
...  
Keyword(s):  
Electron Density ◽  
Particle Density ◽  
Small Scale ◽  
Mesopause Region ◽  
Ice Particles ◽  
Summer Echoes ◽  
Outer Atmosphere ◽  
Moist Condition ◽  
Scale Structures ◽  
Small Scale Structures

Abstract. In this paper, a growth and motion model is developed to investigate the evolution of radius, velocity, and number density of ice particles in mesopause region. In the growth model, meteoric dust from outer atmosphere and grains moving with the upward neutral wind from the mesosphere bottom serve as nuclei upon which water vapor can condense in the cold and moist condition. And the motion of the ice particles is mainly controlled by the gravity and the neutral drag force. It is shown that the radius of ice particles increases linearly with time. But the particle velocity has a complicated relationship with the radius due to the different mass densities of condensation nuclei and absorbed ice. For certain condensation core radius, the velocity of particles can be reversed at particular height, which leads to local gathering of particles near the boundary layer and small-scale structures of ice particle density on the order of a few meters. Based on the obtained small-scale ice particle distribution, the mean particle charge number and corresponding distributions of electrons are calculated by combining the dust charging processes and quasi-neutrality condition. It shows that the absorption of electrons by ice particles results in the formation of small-scale electron density structures, which can be important to the research on the cause of polar mesosphere summer echoes (PMSE).

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