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

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.

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

2021 ◽  
Author(s):  
René Sedlak ◽  
Patrick Hannawald ◽  
Carsten Schmidt ◽  
Sabine Wüst ◽  
Michael Bittner ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Lower Thermosphere ◽  
Image Data ◽  
Eddy Diffusion ◽  
Dissipated Energy ◽  
Heating Rates ◽  
Wind Fields ◽  
Broadband Emission ◽  
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/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.

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

2018 ◽  
Vol 11 (8) ◽  
pp. 4891-4907 ◽  
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.

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

Atmosphere ◽  
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.

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

1999 ◽  
Vol 24 (11) ◽  
pp. 1571-1576 ◽  
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

scholarly journals Nocturnal Elevated Convection Initiation of the PECAN 4 July Hailstorm

2018 ◽  
Vol 146 (1) ◽  
pp. 243-262 ◽  
Author(s):  
J. W. Wilson ◽  
S. B. Trier ◽  
D. W. Reif ◽  
R. D. Roberts ◽  
T. M. Weckwerth
Keyword(s):  
Gravity Waves ◽  
University Of Wyoming ◽  
Cloud Base ◽  
Doppler Lidar ◽  
Convective Storms ◽  
Multiple Observations ◽  
Western Side ◽  
Convection Initiation ◽  
The University ◽  
Advance Knowledge

AbstractDuring the Plains Elevated Convection at Night (PECAN) experiment, an isolated hailstorm developed on the western side of the PECAN study area on the night of 3–4 July 2015. One of the objectives of PECAN was to advance knowledge of the processes and conditions leading to pristine nocturnal convection initiation (CI). This nocturnal hailstorm developed more than 160 km from any other convective storms and in the absence of any surface fronts or bores. The storm initiated within 110 km of the S-Pol radar; directly over a vertically pointing Doppler lidar; within 25 km of the University of Wyoming King Air flight track; within a network of nine sounding sites taking 2-hourly soundings; and near a mobile mesonet track. Importantly, even beyond 100 km in range, S-Pol observed the preconvection initiation cloud that was collocated with the satellite infrared cloud image and provided information on the evolution of cloud growth. The multiple observations of cloud base, thermodynamic stability, and direct updraft observations were used to determine that the updraft roots were elevated. Diagnostic analysis presented in the paper suggests that CI was aided by lower-tropospheric gravity waves occurring in an environment of weak but persistent mesoscale lifting.

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

2018 ◽  
Vol 75 (10) ◽  
pp. 3635-3651 ◽  
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.

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

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&deg;S, 46&deg;W), while all-sky images of multiple airglow layers provided amplitudes and parameters of waves over Cachoeira Paulista (23&deg;S, 45&deg;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.

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

2015 ◽  
Vol 15 (9) ◽  
pp. 4997-5005 ◽  
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.

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

2008 ◽  
Vol 65 (2) ◽  
pp. 557-575 ◽  
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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