scholarly journals Advanced hodograph-based analysis technique to derive gravity waves parameters from Lidar observations

2019 ◽  
Author(s):  
Irina Strelnikova ◽  
Gerd Baumgarten ◽  
Franz-Josef Lübken
Keyword(s):  
Gravity Waves ◽  
Kinetic Energy Density ◽  
Linear Wave ◽  
Altitude Range ◽  
Hodograph Method ◽  
Preferred Direction ◽  
Background Removal ◽  
Analysis Technique ◽  
Propagating Waves ◽  
Lidar Observations

Abstract. An advanced hodograph-based analysis technique to derive gravity waves (GW) parameters from observations of temperature and winds is developed and presented as a step-by-step recipe with justification of every step in such an analysis. As a most adequate background removal technique the 2D-FFT is suggested. For an unbiased analysis of fluctuation whose amplitude grows with height exponentially we propose to apply a scaling function of the form exp(z/(ςH)), where H is scale height, z is altitude, and the constant ς can be derived by a linear fit to fluctuation profiles and should be in a range 1–10 (we derived ς = 2.15 for our data). The most essential part of the proposed analysis technique consist of fitting of cosines- waves to simultaneously measured profiles of zonal and meridional winds and temperature and subsequent hodograph analysis of these fitted waves. The novelty of our approach is that its robustness ultimately allows for automation of the hodograph analysis and resolves many more GWs than it can be inferred by manually applied hodograph technique. This technique is applied to unique lidar measurements of temperature and horizontal winds measured in an altitude range of 30 to 70 km. A case study of continuous lidar observations from January 09 to 12, 2016 with the ALOMAR Rayleigh-Mie-Raman (RMR) Lidar in Northern Norway (69° N) is analyzed. We use linear wave theory to identify 4507 quasi monochromatic waves and apply the hodograph method which allows to estimate several important parameters of the observed GW. This technique allows to unambiguously identify up- and downward propagating GW. In the vicinity of the polar night jet ∼ 30 % of the detected 15 waves propagate downwards. The upward propagating GW predominantly propagate against the background wind, whereas downward propagating waves show no preferred direction. The kinetic energy density of upward propagating GW is larger than that of the downward propagating waves, whereas the potential energy is nearly the same for both directions. The mean vertical flux of horizontal momentum in the altitude range of 42 to 70 km for the detected waves is about 0.65 mPa for upward propagating GW and 0.53 mPa for downward propagating GW.

scholarly journals Advanced hodograph-based analysis technique to derive gravity-wave parameters from lidar observations

2020 ◽  
Vol 13 (2) ◽  
pp. 479-499
Author(s):  
Irina Strelnikova ◽  
Gerd Baumgarten ◽  
Franz-Josef Lübken
Keyword(s):  
Gravity Wave ◽  
Wave Theory ◽  
Linear Wave ◽  
Data Set ◽  
Background Removal ◽  
Analysis Technique ◽  
Lidar Measurements ◽  
Meridional Winds ◽  
Linear Fit ◽  
Removal Technique

Abstract. An advanced hodograph-based analysis technique to derive gravity-wave (GW) parameters from observations of temperature and winds is developed and presented as a step-by-step recipe with justification for every step in such an analysis. As the most adequate background removal technique the 2-D FFT is suggested. For an unbiased analysis of fluctuation whose amplitude grows with height exponentially, we propose applying a scaling function of the form exp (z∕(ςH)), where H is scale height, z is altitude, and the constant ς can be derived by a linear fit to the fluctuation profile and should be in the range 1–10. The most essential part of the proposed analysis technique consists of fitting cosine waves to simultaneously measured profiles of zonal and meridional winds and temperature and subsequent hodograph analysis of these fitted waves. The linear wave theory applied in this analysis is extended by introducing a wave packet envelope term exp⁡(-(z-z0)2/2σ2) that accounts for limited extent of GWs in the observational data set. The novelty of our approach is that its robustness ultimately allows for automation of the hodograph analysis and resolves many more GWs than can be inferred by the manually applied hodograph technique. This technique allows us to unambiguously identify upward- and downward-propagating GWs and their parameters. This technique is applied to unique lidar measurements of temperature and horizontal winds measured in an altitude range of 30 to 70 km.

Lidar Observations of Seasonal Variability of Gravity-Waves

2020 ◽  
Author(s):  
Irina Strelnikova ◽  
Gerd Baumgarten ◽  
Franz-Josef Lübken
Keyword(s):  
Gravity Waves ◽  
Phase Speed ◽  
Meridional Wind ◽  
Vertical Coupling ◽  
Wave Characteristics ◽  
Long Duration ◽  
Analysis Technique ◽  
Propagating Waves ◽  
Recent Developments ◽  
Volume Measurements

<p><span>In order to understand </span><span>the </span><span>generation, propagation and climatology of gravity waves (GWs)observations with high temporal and vertical resolution are required. </span><span>The observation of gravity waves</span> <span>is </span><span>important </span><span>to understand the </span><span>vertical coupling in the atmosphere.<br><br>Recent developments in lidar technology give us new possibilities to study GWs experimentally on a more or less regular basis and resolve spatial sales of 150 </span><span>meters</span><span> in </span><span>the </span><span>vertical and temporal scales of </span><span>about 10</span><span> min</span><span>utes</span><span>. In particular, the capabilit</span><span>y to operate the lidar during daytime</span><span> allow</span><span>s</span><span> for long duration GW observations. The Doppler Rayleigh Iodine Spectrometer (DoRIS) </span><span>in addition</span><span>to the established </span><span>hydrostatic </span><span>temperature measurement </span><span>technique</span><span> yields simultaneous </span><span>and</span><span> common volume measurements of winds.<br><br>At the ALOMAR observatory in northern Norway (69°N, 16°E) </span><span>the </span><span>gravity wave potential energy density (GWPED) in the stratosphere is shown to have a large seasonal variation with a maximum in winter and a minimum in summer.<br><br>In this work we use the phase relation between both zonal and meridional wind components and temperature. We study gravity waves sorted for up- and downward propagating waves under summer and winter conditions to investigate different wave propagation and generation scenarios. We discuss the winter/summer difference not only in terms of total GWPED, but in terms of wave characteristics obtained from our extended analysis technique. We demonstrate, for example, that amount of downward propagating waves is larger in winter than in summer. Also, other wave characteristics like phase speed and mean intrinsic period </span><span>will be discussed</span><span>.</span></p>

scholarly journals Lidar observations of persistent gravity waves with periods of 3–10 h in the Antarctic middle and upper atmosphere at McMurdo (77.83°S, 166.67°E)

2016 ◽  
Vol 121 (2) ◽  
pp. 1483-1502 ◽  
Author(s):  
Cao Chen ◽  
Xinzhao Chu ◽  
Jian Zhao ◽  
Brendan R. Roberts ◽  
Zhibin Yu ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Upper Atmosphere ◽  
The Antarctic ◽  
Lidar Observations

scholarly journals Deep Subwavelength Power Concentration-Based Hyperbolic Metamaterials

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Amanpreet Kaur ◽  
Saptarshi Banerjee ◽  
Wangshi Zhao ◽  
Jayanti Venkataraman ◽  
Zhaolin Lu
Keyword(s):  
Electromagnetic Waves ◽  
Light Propagation ◽  
Spot Size ◽  
Diffraction Limit ◽  
Evanescent Waves ◽  
Hyperbolic Metamaterials ◽  
Preferred Direction ◽  
Propagating Waves ◽  
Medium Design ◽  
Collimated Beam

Hyperbolic metamaterials can manipulate electromagnetic waves by converting evanescent waves into propagating waves and thus support light propagation without diffraction limit. In this paper, deep subwavelength focusing (or power concentration) is demonstrated both numerically and experimentally using hyperbolic metamaterials. The results verify that hyperbolic metamaterials can focus a broad collimated beam to spot size of ~λ0/6 using wired medium design for both normal and oblique incidence. The nonmagnetic design, no-cut-off operation, and preferred direction of propagation in these materials significantly reduce the attenuation in electromagnetic waves.

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°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.

scholarly journals Gravity wave amplitudes and momentum fluxes inferred from OH airglow intensities and meteor radar winds during SpreadFEx

2009 ◽  
Vol 27 (6) ◽  
pp. 2361-2369 ◽  
Author(s):  
F. Vargas ◽  
D. Gobbi ◽  
H. Takahashi ◽  
L. M. Lima
Keyword(s):  
Gravity Waves ◽  
Horizontal Wind ◽  
Small Scale ◽  
Meteor Radar ◽  
Plasma Bubble ◽  
Spatial And Temporal Scales ◽  
Analysis Technique ◽  
Momentum Fluxes ◽  
Different Types ◽  
Wave Directionality

Abstract. We show in this report the momentum flux content input in the mesosphere due to relatively fast and small scale gravity waves (GWs) observed through OH airglow images. The acquisition of OH NIR images was carried out in Brazil at Brasilia (14.8° S, 47.6° W) and Cariri (7.4° S, 36.5° W) from September 2005 to November 2005 during the SpreadFEx Campaign. Horizontal wind information from meteor radar was available in Cariri only. Our findings showed strong wave activity in both sites, mainly in Cariri. High wave directionality was also observed in both sites during SpreadFEx, which have been observed by other investigators using different analysis' techniques and different types of data during the campaign. We discuss also the possibility of plasma bubble seeding by gravity waves presenting spatial and temporal scales estimated with our novel analysis technique during the SpreadFEx campaign.

scholarly journals Application of tomographic inversion in studying airglow in the mesopause region

1998 ◽  
Vol 16 (10) ◽  
pp. 1180-1189 ◽  
Author(s):  
T. Nygrén ◽  
M. J. Taylor ◽  
M. S. Lehtinen ◽  
M. Markkanen
Keyword(s):  
Gravity Waves ◽  
Random Noise ◽  
A Priori ◽  
Lower Thermosphere ◽  
Vertical Plane ◽  
Simulated Data ◽  
Altitude Range ◽  
Priori Information ◽  
Two Stages ◽  
Atmospheric Gravity

Abstract. It is pointed out that observations of periodic nightglow structures give excellent information on atmospheric gravity waves in the mesosphere and lower thermosphere. The periods, the horizontal wavelengths and the phase speeds of the waves can be determined from airglow images and, using several cameras, the approximate altitude of the luminous layer can also be determined by triangulation. In this paper the possibility of applying tomographic methods for reconstructing the airglow structures is investigated using numerical simulations. A ground-based chain of cameras is assumed, two-dimensional airglow models in the vertical plane above the chain are constructed, and simulated data are calculated by integrating the models along a great number of rays with different elevation angles for each camera. After addition of random noise, these data are then inverted to obtain reconstructions of the models. A tomographic analysis package originally designed for satellite radiotomography is used in the inversion. The package is based on a formulation of stochastic inversion which allows the input of a priori information to the solver in terms of regularization variances. The reconstruction is carried out in two stages. In the first inversion, constant regularization variances are used within a wide altitude range. The results are used in determining the approximate altitude range of the airglow structures. Then, in the second inversion, constant non-zero regularization variances are used inside this region and zero variances outside it. With this method reliable reconstructions of the models are obtained. The number of cameras as well as their separations are varied in order to find out the limitations of the method.Key words. Tomography · Airglow · Mesopause · Gravity waves

Radiation of short waves from the resonantly excited capillary–gravity waves

2016 ◽  
Vol 810 ◽  
pp. 5-24 ◽  
Author(s):  
M. Hirata ◽  
S. Okino ◽  
H. Hanazaki
Keyword(s):  
Solitary Wave ◽  
Solitary Waves ◽  
Gravity Waves ◽  
Wave Pattern ◽  
Short Wave ◽  
Bond Number ◽  
Linear Wave ◽  
Cnoidal Wave ◽  
Short Waves ◽  
Long Wave

Capillary–gravity waves resonantly excited by an obstacle (Froude number: $Fr=1$) are investigated by the numerical solution of the Euler equations. The radiation of short waves from the long nonlinear waves is observed when the capillary effects are weak (Bond number: $Bo<1/3$). The upstream-advancing solitary wave radiates a short linear wave whose phase velocity is equal to the solitary waves and group velocity is faster than the solitary wave (soliton radiation). Therefore, the short wave is observed upstream of the foremost solitary wave. The downstream cnoidal wave also radiates a short wave which propagates upstream in the depression region between the obstacle and the cnoidal wave. The short wave interacts with the long wave above the obstacle, and generates a second short wave which propagates downstream. These generation processes will be repeated, and the number of wavenumber components in the depression region increases with time to generate a complicated wave pattern. The upstream soliton radiation can be predicted qualitatively by the fifth-order forced Korteweg–de Vries equation, but the equation overestimates the wavelength since it is based on a long-wave approximation. At a large Bond number of $Bo=2/3$, the wave pattern has the rotation symmetry against the pattern at $Bo=0$, and the depression solitary waves propagate downstream.

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