scholarly journals Simultaneous lidar observations of temperatures and waves in the polar middle atmosphere on the east and west side of the Scandinavian mountains: a case study on 19/20 January 2003

2004 ◽  
Vol 4 (3) ◽  
pp. 809-816 ◽  
Author(s):  
U. Blum ◽  
K. H. Fricke ◽  
G. Baumgarten ◽  
A. Schöch
Keyword(s):  
Gravity Waves ◽  
Middle Atmosphere ◽  
Temperature Structure ◽  
Vertical Wavelength ◽  
West Side ◽  
Simultaneous Measurements ◽  
Wave Patterns ◽  
East And West ◽  
The Difference ◽  
Atmospheric Gravity

Abstract. Atmospheric gravity waves have been the subject of intense research for several decades because of their extensive effects on the atmospheric circulation and the temperature structure. The U. Bonn lidar at the Esrange and the ALOMAR RMR lidar at the Andøya Rocket Range are located in northern Scandinavia 250 km apart on the east and west side of the Scandinavian mountain ridge. During January and February 2003 both lidar systems conducted measurements and retrieved atmospheric temperatures. On 19/20 January 2003 simultaneous measurements for more than 7 h were possible. Although during most of the campaign time the atmosphere was not transparent for the propagation of orographically induced gravity waves, they were nevertheless observed at both lidar stations with considerable amplitudes during these simultaneous measurements. And while the source of the observed waves cannot be determined unambiguously, the observations show many characteristics of orographically excited gravity waves. The wave patterns at ALOMAR show a random distribution with time whereas at the Esrange a persistency in the wave patterns is observable. This persistency can also be found in the distribution of the most powerful vertical wavelengths. The mode values are both at about 5 km vertical wavelength, however the distributions are quite different, narrow at the Esrange with values from λz=2–6 km and broad at ALOMAR, covering λz=1–12 km vertical wavelength. In particular the difference between the observations at ALOMAR and at the Esrange can be understood by different orographic conditions while the propagation conditions were quite similar. At both stations the waves deposit energy in the atmosphere with increasing altitude, which leads to a decrease of the observed gravity wave potential energy density with altitude. The meteorological situation during these measurements was different from common winter situations. The ground winds were mostly northerlies, changed in the upper troposphere and lower stratosphere to westerlies and returned to northerlies in the middle stratosphere.

scholarly journals Simultaneous lidar observations of temperatures and waves in the polar middle atmosphere on both sides of the Scandinavian mountains: a case study on 19/20 January 2003

2004 ◽  
Vol 4 (1) ◽  
pp. 969-989 ◽  
Author(s):  
U. Blum ◽  
K. H. Fricke ◽  
G. Baumgarten ◽  
A. Schöch
Keyword(s):  
Gravity Waves ◽  
Middle Atmosphere ◽  
Temperature Structure ◽  
Vertical Wavelength ◽  
Mountain Ridge ◽  
Induced Gravity ◽  
Simultaneous Measurements ◽  
Wave Patterns ◽  
Atmospheric Gravity

Abstract. Atmospheric gravity waves have been the subject of intense research for several decades because of their extensive effects on the atmospheric circulation and the temperature structure. The U. Bonn lidar at the Esrange and the ALOMAR RMR lidar at the Andøya Rocket Range are located in northern Scandinavia 250 km apart on either side of the Scandinavian mountain ridge. During January and February 2003 both lidar systems conducted measurements and retrieved atmospheric temperatures. On 19/20 January 2003 simultaneous measurements for more than 7 h were possible. Although during most of the campaign time the atmosphere was not transparent for the propagation of orographically induced gravity waves, they could propagate and were observed at both lidar stations during these simultaneous measurements. The wave patterns at ALOMAR show a random distribution with time whereas at the Esrange a persistency in the wave patterns is observable. This persistency can also be found in the distribution of the most powerful vertical wavelengths. The mode values are both at about 5 km vertical wavelength, however the distributions are quite different, narrow at the Esrange containing values from λz=2–6 km and broad at ALOMAR, covering λz=1–12 km vertical wavelength. At both stations the waves deposit energy in the atmosphere with increasing altitude, which leads to a decrease of the observed gravity wave potential energy density with altitude. These measurements show unambigiously orographically induced gravity waves on both sides of the mountains as well as a clear difference of the characteristics of these waves, which might be caused by different excitation and propagation conditions on either side of the Scandinavian mountain ridge.

scholarly journals On the role of dust storms in triggering atmospheric gravity waves observed in the middle atmosphere

2011 ◽  
Vol 29 (9) ◽  
pp. 1647-1654 ◽  
Author(s):  
S. K. Das ◽  
A. Taori ◽  
A. Jayaraman
Keyword(s):  
Gravity Waves ◽  
Dust Storm ◽  
Hot Spots ◽  
Middle Atmosphere ◽  
Thermal Structure ◽  
Dust Storms ◽  
Storm Events ◽  
Atmospheric Perturbations ◽  
Atmospheric Gravity

Abstract. Lower atmospheric perturbations often produce measurable effects in the middle and upper atmosphere. The present study demonstrates the response of the middle atmospheric thermal structure to the significant enhancement of the lower atmospheric heating effect caused by dust storms observed over the Thar Desert, India. Our study from multi-satellite observations of two dust storm events that occurred on 3 and 8 May 2007 suggests that dust storm events produce substantial changes in the lower atmospheric temperatures as hot spots which can become sources for gravity waves observed in the middle atmosphere.

Simultaneous ionosonde investigations of the ionospheric F2 layer critical frequency and peak height at both ends of the geomagnetic tube

2020 ◽  
Vol 1 (1) ◽  
pp. 31-44
Author(s):  
Sergii Panasenko ◽  
Dmytro Kotov ◽  
Taras Zhivolup ◽  
Olexander Koloskov ◽  
Volodymyr Lisachenko
Keyword(s):  
Gravity Waves ◽  
Critical Frequency ◽  
Peak Height ◽  
Ionospheric Disturbances ◽  
Atmospheric Gravity Waves ◽  
Magnetohydrodynamic Waves ◽  
Traveling Ionospheric Disturbances ◽  
Critical Frequency Fof2 ◽  
The Difference ◽  
Atmospheric Gravity

Based on the results of simultaneous ionosonde observations during low solar and weak magnetic activities, a coupling was found between diurnal and quasi-periodic variations in ionospheric parameters over magnetically conjugated regions, where the Ukrainian Antarctic Station (UAS) and Millstone Hill Observatory are located. A significant impact of the summer hemisphere on the nighttime variations of the F2 layer critical frequency foF2 in the magnetically conjugated region in the winter hemisphere was found. The most characteristic manifestation of this impact is the control of foF2 variations over the UAS not by the local sunset (sunrise), but by the sunset (sunrise) over Millstone Hill. It was found that the sunset over Millstone Hill leads to an increase in foF2 over the UAS, while the sunrise leads to a decrease in foF2 with a subsequent sharp increase. Both phenomena are associated with changes in the photoelectron flux from the northern hemisphere, corresponding changes in the electron temperature in the ionosphere above the UAS and the effect of these changes on the compression or rarefaction of the ionospheric plasma and changes in the plasmaspheric fluxes of H + ions. It was shown that the transition from nighttime to daytime conditions over both observation points was characterized by a significant decrease in the F2 layer peak height, and the difference in the values of this ionospheric parameter over Millstone Hill and UAS at night is due to seasonal differences in the thermospheric circulation and the difference in the behavior of the ionospheric parameters in the Northern and Southern hemispheres. Manifestations of atmospheric gravity waves, caused by the passage of local sunrise terminators, as traveling ionospheric disturbances with periods of about 90 and 75 – 120 mins over Millstone Hill and UAS, respectively, were found. These waves were most likely generated in the region located between the ionospheric F1 and F2 layers, where the sharp gradients in the electron and ion densities occur during changes in the intensity of solar radiation. It is confirmed that wave disturbances in atmospheric and ionospheric parameters can be transferred between magnetically conjugated regions by slow magnetohydrodynamic waves generated both at the heights of the ionospheric dynamo region due to the modulation of atmospheric and ionospheric parameters by atmospheric waves and the occurrence of external currents, and at the top of the plasmaspheric tube, where sharp plasma compression and heating or rarefaction and cooling occur during the passage of the solar terminator. Keywords: the ionosphere, F2 region, ionosonde measurements, geomagnetic field tube, magnetoconjugate region coupling, atmospheric gravity waves, traveling ionospheric disturbances, generation of slow magnetohydrodynamic waves

scholarly journals Seasonal Cycle of Gravity Wave Potential Energy Densities from Lidar and Satellite Observations at 54° and 69°N

2021 ◽  
Vol 78 (4) ◽  
pp. 1359-1386
Author(s):  
Irina Strelnikova ◽  
Marwa Almowafy ◽  
Gerd Baumgarten ◽  
Kathrin Baumgarten ◽  
Manfred Ern ◽  
...  
Keyword(s):  
Potential Energy ◽  
Gravity Wave ◽  
Seasonal Cycle ◽  
Middle Atmosphere ◽  
Reanalysis Data ◽  
Vertical Wavelength ◽  
Wave Potential ◽  
Broadband Emission ◽  
The Difference ◽  
Lidar Observations

AbstractWe present gravity wave climatologies based on 7 years (2012–18) of lidar and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperatures and reanalysis data at 54° and 69°N in the altitude range 30–70 km. We use 9452 (5044) h of lidar observations at Kühlungsborn [Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR)]. Filtering according to vertical wavelength (λz < 15 km) or period (τ < 8 h) is applied. Gravity wave potential energy densities (GWPED) per unit volume (EpV) and per unit mass (Epm) are derived. GWPED from reanalysis are smaller compared to lidar. The difference increases with altitude in winter and reaches almost two orders of magnitude around 70 km. A seasonal cycle of EpV with maximum values in winter is present at both stations in nearly all lidar and SABER measurements and in reanalysis data. For SABER and for lidar (with λ < 15 km) the winter/summer ratios are a factor of ~2–4, but are significantly smaller for lidar with τ < 8 h. The winter/summer ratios are nearly identical at both stations and are significantly larger for Epm compared to EpV. Lidar and SABER observations show that EpV is larger by a factor of ~2 at Kühlungsborn compared to ALOMAR, independent of season and altitude. Comparison with mean background winds shows that simple scenarios regarding GW filtering, etc., cannot explain the Kühlungsborn–ALOMAR differences. The value of EpV decreases with altitude in nearly all cases. Corresponding EpV-scale heights from lidar are generally larger in winter compared to summer. Above ~55 km, EpV in summer is almost constant with altitude at both stations. The winter–summer difference of EpV scale heights is much smaller or absent in SABER and in reanalysis data.

scholarly journals Automatic Extraction of Gravity Waves from All-Sky Airglow Image Based on Machine Learning

2019 ◽  
Vol 11 (13) ◽  
pp. 1516 ◽  
Author(s):  
Chang Lai ◽  
Jiyao Xu ◽  
Jia Yue ◽  
Wei Yuan ◽  
Xiao Liu ◽  
...  
Keyword(s):  
Neural Network ◽  
Object Detection ◽  
Convolutional Neural Network ◽  
Gravity Waves ◽  
Classification Model ◽  
Atmospheric Gravity Waves ◽  
Detection Model ◽  
Wave Patterns ◽  
Airglow Image ◽  
Atmospheric Gravity

With the development of ground-based all-sky airglow imager (ASAI) technology, a large amount of airglow image data needs to be processed for studying atmospheric gravity waves. We developed a program to automatically extract gravity wave patterns in the ASAI images. The auto-extraction program includes a classification model based on convolutional neural network (CNN) and an object detection model based on faster region-based convolutional neural network (Faster R-CNN). The classification model selects the images of clear nights from all ASAI raw images. The object detection model locates the region of wave patterns. Then, the wave parameters (horizontal wavelength, period, direction, etc.) can be calculated within the region of the wave patterns. Besides auto-extraction, we applied a wavelength check to remove the interference of wavelike mist near the imager. To validate the auto-extraction program, a case study was conducted on the images captured in 2014 at Linqu (36.2°N, 118.7°E), China. Compared to the result of the manual check, the auto-extraction recognized less (28.9% of manual result) wave-containing images due to the strict threshold, but the result shows the same seasonal variation as the references. The auto-extraction program applies a uniform criterion to avoid the accidental error in manual distinction of gravity waves and offers a reliable method to process large ASAI images for efficiently studying the climatology of atmospheric gravity waves.

scholarly journals Formation of Multilayered Sporadic E under an Influence of Atmospheric Gravity Waves (AGWs)

Atmosphere ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 653
Author(s):  
Goderdzi G. Didebulidze ◽  
Giorgi Dalakishvili ◽  
Maya Todua
Keyword(s):  
Phase Velocity ◽  
Wind Velocity ◽  
Drift Velocity ◽  
Gravity Waves ◽  
Lower Thermosphere ◽  
Metallic Ions ◽  
Vertical Wavelength ◽  
Vertical Drift ◽  
Sporadic E ◽  
Atmospheric Gravity

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.

Atmospheric Gravity Waves in ADM-Aeolus Wind Lidar Observations

2021 ◽  
Author(s):  
Timothy Banyard ◽  
Corwin Wright ◽  
Neil Hindley ◽  
Gemma Halloran ◽  
Isabell Krisch ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Phase Structure ◽  
Critical Role ◽  
Spatial Location ◽  
Horizontal Wind ◽  
Vertical Wavelength ◽  
Wind Lidar ◽  
Atmospheric Gravity ◽  
Lidar Observations

&lt;p&gt;&lt;span&gt;As the first Doppler wind lidar in space, ADM-Aeolus provides us with a unique opportunity to study the propagation of gravity waves (GWs) from the surface to the tropopause and UTLS. Existing space-based measurements of GWs in this altitude range are spatially limited and, where available, use temperature as a proxy for wind perturbations. Thus, space-borne wind lidars such as Aeolus have the potential to transform our understanding of these critically-important dynamical processes. Here, we present the first observations of GWs in Aeolus data. We analyse a case study of a large orographic GW over the Southern Andes in July 2019 which is clearly visible in the horizontal wind. This example demonstrates the capability of Aeolus to measure the phase structure of GWs from near the surface up into the stratosphere. We validate these results against temperature-based observations from the AIRS nadir sounder and CORAL lidar, and also against ERA5 wind and temperature. There is close agreement in phase structure between Aeolus and the validation datasets, and with a near-identical observed vertical wavelength and spatial location. This case study suggests that data from Aeolus, and similar next-generation space-borne wind lidars, could play a critical role in constraining future model GW parameterisations, with the potential to significantly broaden our understanding of atmospheric dynamics.&lt;/span&gt;&lt;/p&gt;

scholarly journals Observations of in-situ generated gravity waves during a stratospheric temperature enhancement (STE) event

2011 ◽  
Vol 11 (22) ◽  
pp. 11913-11917 ◽  
Author(s):  
A. J. Gerrard ◽  
Y. Bhattacharya ◽  
J. P. Thayer
Keyword(s):  
Gravity Waves ◽  
Background Wind ◽  
Wind Fields ◽  
Vertical Wavelength ◽  
Stratospheric Temperature ◽  
Wave Parameters ◽  
Phase Progression ◽  
Temperature Enhancement ◽  
Atmospheric Gravity

Abstract. Evidence for in situ generated atmospheric gravity waves associated with a stratospheric temperature enhancement (STE) are presented. The signatures of two sets of gravity waves are observed by molecular-aerosol lidar in conjunction with the early December 2000 STE event above Sondrestrom, Greenland. The first set of gravity waves shows downward phase progression with a vertical wavelength of ~8 km while the second set shows upward phase progression with a vertical wavelength of ~9 km. With estimates of the background wind fields from synoptic analyses, the various intrinsic gravity wave parameters of these two wave structures are found. The observed wave features compare well to previous numerical modeling predictions.

scholarly journals Nonlinear interaction of gravity waves in a nonisothermal and dissipative atmosphere

2014 ◽  
Vol 32 (3) ◽  
pp. 263-275 ◽  
Author(s):  
K. M. Huang ◽  
S. D. Zhang ◽  
F. Yi ◽  
C. M. Huang ◽  
Q. Gan ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Wave Energy ◽  
Nonlinear Interaction ◽  
Numerical Experiments ◽  
Energy Exchange ◽  
Middle Atmosphere ◽  
Vertical Wavelength ◽  
Fully Nonlinear Equations ◽  
Inhomogeneous Temperature ◽  
Inhomogeneous Temperature Field

Abstract. Starting from a set of fully nonlinear equations, this paper studies that two initial gravity wave packets interact to produce a third substantial packet in a nonisothermal and dissipative atmosphere. The effects of the inhomogeneous temperature and dissipation on interaction are revealed. Numerical experiments indicate that significant energy exchange occurs through the nonlinear interaction in a nonisothermal and dissipative atmosphere. Because of the variability of wavelengths and frequencies of interacting waves, the interaction in an inhomogeneous temperature field is characterised by the nonresonance. The nonresonant three waves mismatch mainly in the vertical wavelengths, but match in the horizontal wavelengths, and their frequencies also tend to match throughout the interaction. Below 80 km, the influence of atmospheric dissipation on the interaction is rather weak due to small diffusivities. With the further propagation of wave above 80 km, the exponentially increasing atmospheric dissipation leads to the remarkable decay and slowly upward propagation of wave energy. Even so, the dissipation below 110 km is not enough to decrease the vertical wavelength of wave. The dissipation seems neither to prevent the interaction occurrence nor to prolong the period of wave energy exchange, which is different from the theoretical prediction based on the linearised equations. The match relationship and wave energy evolution in numerical experiments are helpful in further investigating interaction of gravity waves in the middle atmosphere based on experimental observations.

Improved Middle Atmosphere Climate and Forecasts in the ECMWF Model through a Nonorographic Gravity Wave Drag Parameterization

2010 ◽  
Vol 23 (22) ◽  
pp. 5905-5926 ◽  
Author(s):  
Andrew Orr ◽  
Peter Bechtold ◽  
John Scinocca ◽  
Manfred Ern ◽  
Marta Janiskova
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Middle Atmosphere ◽  
Forecast Error ◽  
Wave Structure ◽  
Stationary Wave ◽  
Wave Drag ◽  
Horizontal Distribution ◽  
Small Scale ◽  
Temperature Structure

Abstract In model cycle 35r3 (Cy35r3) of the ECMWF Integrated Forecast System (IFS), the momentum deposition from small-scale nonorographic gravity waves is parameterized by the Scinocca scheme, which uses hydrostatic nonrotational wave dynamics to describe the vertical evolution of a broad, constant, and isotropic spectrum of gravity waves emanating from the troposphere. The Cy35r3 middle atmosphere climate shows the following: (i) an improved representation of the zonal-mean circulation and temperature structure; (ii) a realistic parameterized gravity wave drag; (iii) a reasonable stationary planetary wave structure and stationary wave driving in July and an underestimate of the generation of stationary wave activity in the troposphere and stationary wave driving in January; (iv) an improved representation of the tropical variability of the stratospheric circulation, although the westerly phase of the semiannual oscillation is missing; and (v) a realistic horizontal distribution of momentum flux in the stratosphere. By contrast, the middle atmosphere climate is much too close to radiative equilibrium when the Scinocca scheme is replaced by Rayleigh friction, which was the standard method of parameterizing the effects of nonorographic gravity waves in the IFS prior to Cy35r3. Finally, there is a reduction in Cy35r3 short-range high-resolution forecast error in the upper stratosphere.

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