Gravity wave instability structures and turbulence from more than one and a half years of OH* airglow imager observations in Slovenia

Abstract. We analysed 286 nights of data from the OH* airglow imager FAIM 3 (Fast Airglow IMager) acquired at Otlica Observatory (45.93 °N, 13.91 °E), Slovenia between 26 October 2017 and 6 June 2019. Measurements have been performed with a spatial resolution of 24 m/pixel and a temporal resolution of 2.8 s. A two-dimensional Fast Fourier transform is applied to the image data to derive horizontal wavelengths between 48 m and 4.5 km in the upper mesosphere / lower thermosphere (UMLT) region. In contrast to the statistics of larger scale gravity waves (horizontal wavelength up to ca. 50 km) we find a more isotropic distribution of directions of propagation, pointing to the presence of wave structures created above the stratospheric wind fields. A weak seasonal tendency of a majority of waves propagating eastward (westward) during winter (summer) may be due to secondary gravity waves originating from breaking primary waves in the stratosphere. We also observe an increased southward propagation during summer, which we interpret as an enhanced contribution of secondary gravity waves created as a consequence of primary wave filtering by the meridional mesospheric circulation. Furthermore, observations of turbulent vortices allowed the estimation of eddy diffusion coefficients in the UMLT from image sequences in 45 cases. Values range around 103–104 m2s-1 and mostly agree with literature. Turbulently dissipated energy is derived taking into account values of the Brunt-Väisälä frequency based on TIMED-SABER (Thermosphere Ionosphere Mesosphere Energetics Dynamics, Sounding of the Atmosphere using Broadband Emission Radiometry) measurements. Energy dissipation rates range between 0.63 W/kg and 14.21 W/kg leading to an approximated maximum heating of 0.2–6.3 K per turbulence event. These are in the same range as the daily chemical heating rates, which apparently stresses the importance of dynamical energy conversion in the UMLT.

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Gravity wave instability structures and turbulence from more than 1.5 years of OH* airglow imager observations in Slovenia

Atmospheric Measurement Techniques ◽

10.5194/amt-14-6821-2021 ◽

2021 ◽

Vol 14 (10) ◽

pp. 6821-6833

Author(s):

René Sedlak ◽

Patrick Hannawald ◽

Carsten Schmidt ◽

Sabine Wüst ◽

Michael Bittner ◽

...

Keyword(s):

Gravity Waves ◽

Lower Thermosphere ◽

Image Data ◽

Energy Dissipation Rate ◽

Heating Rates ◽

Wind Fields ◽

Multiple Observations ◽

Isotropic Distribution ◽

Chemical Heating ◽

Stratospheric Wind

Abstract. We analysed 286 nights of data from the OH* airglow imager FAIM 3 (Fast Airglow IMager) acquired at Otlica Observatory (45.93∘ N, 13.91∘ E), Slovenia, between 26 October 2017 and 6 June 2019. Measurements have been performed with a spatial resolution of 24 m per pixel and a temporal resolution of 2.8 s. A two-dimensional fast Fourier transform is applied to the image data to derive horizontal wavelengths between 48 m and 4.5 km in the upper mesosphere/lower thermosphere (UMLT) region. In contrast to the statistics of larger-scale gravity waves (horizontal wavelength up to ca. 50 km; Hannawald et al., 2019), we find a more isotropic distribution of directions of propagation, pointing to the presence of wave structures created above the stratospheric wind fields. A weak seasonal tendency of a majority of waves propagating eastward during winter may be due to instability features from breaking secondary gravity waves that were created in the stratosphere. We also observe an increased southward propagation during summer, which we interpret as an enhanced contribution of secondary gravity waves created as a consequence of primary wave filtering by the meridional mesospheric circulation. We present multiple observations of turbulence episodes captured by our high-resolution airglow imager and estimated the energy dissipation rate in the UMLT from image sequences in 25 cases. Values range around 0.08 and 9.03 W kg−1 and are on average higher than those in recent literature. The values found here would lead to an approximated localized maximum heating of 0.03–3.02 K per turbulence event. These are in the same range as the daily chemical heating rates for the entire atmosphere reported by Marsh (2011), which apparently stresses the importance of dynamical energy conversion in the UMLT.

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Estimates of eddy turbulence consistent with seasonal variations of atomic oxygen and its possible role in the seasonal cycle of mesopause temperature

Annales Geophysicae ◽

10.5194/angeo-28-2103-2010 ◽

2010 ◽

Vol 28 (11) ◽

pp. 2103-2110 ◽

Cited By ~ 8

Author(s):

M. N. Vlasov ◽

M. C. Kelley

Keyword(s):

Diffusion Coefficient ◽

Gravity Waves ◽

Seasonal Variations ◽

Atomic Oxygen ◽

Lower Thermosphere ◽

Eddy Diffusion ◽

Downward Motion ◽

Adiabatic Cooling ◽

Eddy Diffusion Coefficient ◽

The Impact

Abstract. According to current understanding, adiabatic cooling and heating induced by the meridional circulation driven by gravity waves is the major process for the cold summer and warm winter polar upper mesosphere. However, our calculations show that the upward/downward motion needed for adiabatic cooling/heating of the summer/winter polar mesopause simultaneously induces a seasonal variation in both the O maximum density and the altitude of the [O] peak that is opposite to the observed variables generalized by the MSISE-90 model. It is usually accepted that eddy turbulence can produce the [O] seasonal variations. Using this approach, we can infer the eddy diffusion coefficient for the different seasons. Taking these results and experimental data on the eddy diffusion coefficient, we consider in detail and estimate the heating and cooling caused by eddy turbulence in the summer and winter polar upper mesosphere. The seasonal variations of these processes are similar to the seasonal variations of the temperature and mesopause. These results lead to the conclusion that heating/cooling by eddy turbulence is an important component in the energy budget and that adiabatic cooling/heating induced by upward/downward motion cannot dominate in the mesopause region. Our study shows that the impact of the dynamic process, induced by gravity waves, on [O] distributions must be included in models of thermal balance in the upper mesosphere and lower thermosphere (MLT) for a consistent description because (a) the [O] distribution is very sensitive to dynamic processes, and (b) atomic oxygen plays a very important role in chemical heating and infrared cooling in the MLT. To our knowledge, this is the first attempt to consider this aspect of the problem.

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Retrieving horizontally resolved wind fields using multi-static meteor radar observations

Atmospheric Measurement Techniques ◽

10.5194/amt-11-4891-2018 ◽

2018 ◽

Vol 11 (8) ◽

pp. 4891-4907 ◽

Cited By ~ 13

Author(s):

Gunter Stober ◽

Jorge L. Chau ◽

Juha Vierinen ◽

Christoph Jacobi ◽

Sven Wilhelm

Keyword(s):

Gravity Waves ◽

Continuous Wave ◽

Lower Thermosphere ◽

Retrieval Algorithm ◽

Meteor Radar ◽

Wind Fields ◽

Data Set ◽

Wind Retrieval ◽

Radar Network ◽

Frequency Agile

Abstract. Recently, the MMARIA (Multi-static, Multi-frequency Agile Radar for Investigations of the Atmosphere) concept of a multi-static VHF meteor radar network to derive horizontally resolved wind fields in the mesosphere–lower thermosphere was introduced. Here we present preliminary results of the MMARIA network above Eastern Germany using two transmitters located at Juliusruh and Collm, and five receiving links: two monostatic and three multi-static. The observations are complemented during a one-week campaign, with a couple of addition continuous-wave coded transmitters, making a total of seven multi-static links. In order to access the kinematic properties of non-homogenous wind fields, we developed a wind retrieval algorithm that applies regularization to determine the non-linear wind field in the altitude range of 82–98 km. The potential of such observations and the new retrieval to investigate gravity waves with horizontal scales between 50–200 km is presented and discussed. In particular, it is demonstrated that horizonal wavelength spectra of gravity waves can be obtained from the new data set.

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Growth Rate of Gravity Wave Amplitudes Observed in Sodium Lidar Density Profiles and Nightglow Image Data

Atmosphere ◽

10.3390/atmos10120750 ◽

2019 ◽

Vol 10 (12) ◽

pp. 750

Author(s):

Fabio Vargas ◽

Guotao Yang ◽

Paulo Batista ◽

Delano Gobbi

Keyword(s):

Growth Rate ◽

Gravity Wave ◽

Gravity Waves ◽

Growth Rates ◽

Lower Thermosphere ◽

Image Data ◽

Density Profiles ◽

Propagating Waves ◽

Airglow Image ◽

Amplitude Growth

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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Large-Scale Waves in the Mesosphere and Lower Thermosphere Observed by SABER

Journal of the Atmospheric Sciences ◽

10.1175/jas3612.1 ◽

2005 ◽

Vol 62 (12) ◽

pp. 4384-4399 ◽

Cited By ~ 104

Author(s):

Rolando R. Garcia ◽

Ruth Lieberman ◽

James M. Russell ◽

Martin G. Mlynczak

Keyword(s):

Large Scale ◽

Middle Atmosphere ◽

Lower Thermosphere ◽

Normal Modes ◽

Zonal Winds ◽

Broadband Emission ◽

Summer Hemisphere ◽

Mean Structure ◽

Mesosphere And Lower Thermosphere ◽

The Tropics

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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The coupling of planetary waves, tides and gravity waves in the mesosphere and lower thermosphere

Advances in Space Research ◽

10.1016/s0273-1177(99)00881-9 ◽

1999 ◽

Vol 24 (11) ◽

pp. 1571-1576 ◽

Cited By ~ 8

Author(s):

P.J.S. Williams ◽

N.J. Mitchell ◽

A.G. Beard ◽

V.St.C. Howells ◽

H.G. Muller

Keyword(s):

Gravity Waves ◽

Lower Thermosphere ◽

Planetary Waves ◽

Mesosphere And Lower Thermosphere

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The Momentum Budget in the Stratosphere, Mesosphere, and Lower Thermosphere. Part II: The In Situ Generation of Gravity Waves

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-17-0337.1 ◽

2018 ◽

Vol 75 (10) ◽

pp. 3635-3651 ◽

Cited By ~ 6

Author(s):

Ryosuke Yasui ◽

Kaoru Sato ◽

Yasunobu Miyoshi

Keyword(s):

Gravity Wave ◽

Gravity Waves ◽

Lower Thermosphere ◽

Shear Instability ◽

Wave Forcing ◽

Momentum Budget ◽

Mesosphere And Lower Thermosphere ◽

In Situ Generation ◽

Mlt Region

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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Growth Rate of Gravity Wave Amplitudes Observed in Sodium Lidar Density Profiles and Nightglow Image Data

10.20944/preprints201910.0273.v1 ◽

2019 ◽

Author(s):

Fabio Vargas ◽

Guotao Yang ◽

Paulo Batista ◽

Delano Gobbi

Keyword(s):

Growth Rate ◽

Gravity Wave ◽

Gravity Waves ◽

Growth Rates ◽

Image Data ◽

Dynamic Parameters ◽

Density Profiles ◽

Wave Dynamic ◽

Lidar Observations ◽

Amplitude Growth

Amplitude growth rates of monochromatic gravity waves were estimated and compared from multiple instrument measurements carried out in Brazil. Wave dynamic parameters were obtained from sodium density profiles from lidar observations carried out in Sao Jose dos Campos (23°S, 46°W), while all-sky images of multiple airglow layers provided amplitudes and parameters of waves over Cachoeira Paulista (23°S, 45°W). Growth rates of gravity wave amplitudes from lidar and airglow imager data were consistent with dissipative wave behavior. Only a small amount of the observed wave events presented freely propagating behavior. Part of the observed waves presented saturated amplitude. The general saturated/damped behavior is consistent with diffusive filtering processes imposing limits to amplitude growth rates of the observed gravity waves.

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Observations of planetary waves in the mesosphere-lower thermosphere during stratospheric warming events

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-4997-2015 ◽

2015 ◽

Vol 15 (9) ◽

pp. 4997-5005 ◽

Cited By ~ 24

Author(s):

N. H. Stray ◽

Y. J. Orsolini ◽

P. J. Espy ◽

V. Limpasuvan ◽

R. E. Hibbins

Keyword(s):

Climate Model ◽

Lower Thermosphere ◽

Meridional Wind ◽

Wave Number ◽

Stratospheric Warming ◽

Polar Cap ◽

Northern Latitudes ◽

Time Period ◽

Stratospheric Wind ◽

A Chain

Abstract. This study investigates the effect of stratospheric sudden warmings (SSWs) on planetary wave (PW) activity in the mesosphere–lower thermosphere (MLT). PW activity near 95 km is derived from meteor wind data using a chain of eight SuperDARN radars at high northern latitudes that span longitudes from 150° W to 25° E and latitudes from 51 to 66° N. Zonal wave number 1 and 2 components were extracted from the meridional wind for the years 2000–2008. The observed wintertime PW activity shows common features associated with the stratospheric wind reversals and the accompanying stratospheric warming events. Onset dates for seven SSW events accompanied by an elevated stratopause (ES) were identified during this time period using the Specified Dynamics Whole Atmosphere Community Climate Model (SD-WACCM). For the seven events, a significant enhancement in wave number 1 and 2 PW amplitudes near 95 km was found to occur after the wind reversed at 50 km, with amplitudes maximizing approximately 5 days after the onset of the wind reversal. This PW enhancement in the MLT after the event was confirmed using SD-WACCM. When all cases of polar cap wind reversals at 50 km were considered, a significant, albeit moderate, correlation of 0.4 was found between PW amplitudes near 95 km and westward polar-cap stratospheric winds at 50 km, with the maximum correlation occurring ∼ 3 days after the maximum westward wind. These results indicate that the enhancement of PW amplitudes near 95 km is a common feature of SSWs irrespective of the strength of the wind reversal.

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Effects of Nonlinearity on Convectively Forced Internal Gravity Waves: Application to a Gravity Wave Drag Parameterization

Journal of the Atmospheric Sciences ◽

10.1175/2007jas2255.1 ◽

2008 ◽

Vol 65 (2) ◽

pp. 557-575 ◽

Cited By ~ 20

Author(s):

Hye-Yeong Chun ◽

Hyun-Joo Choi ◽

In-Sun Song

Keyword(s):

Gravity Wave ◽

Gravity Waves ◽

Momentum Flux ◽

Lower Thermosphere ◽

Internal Gravity Waves ◽

Wave Drag ◽

Scale Factor ◽

Wide Range ◽

Flux Spectrum ◽

Diabatic Forcing

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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