scholarly journals The interaction between gravity waves and solar tides: Results from 4‐D ray tracing coupled to a linear tidal model

2015 ◽  
Vol 120 (8) ◽  
pp. 6795-6817 ◽  
Author(s):  
B. Ribstein ◽  
U. Achatz ◽  
F. Senf
Keyword(s):  
Ray Tracing ◽  
Gravity Waves ◽  
Tidal Model

Forward ray-tracing for medium-scale gravity waves observed during the COPEX campaign

2012 ◽  
Vol 90-91 ◽  
pp. 117-123 ◽  
Author(s):  
I. Paulino ◽  
H. Takahashi ◽  
S.L. Vadas ◽  
C.M. Wrasse ◽  
J.H.A. Sobral ◽  
...  
Keyword(s):  
Ray Tracing ◽  
Gravity Waves ◽  
Medium Scale

The breaking of transient inertio-gravity waves in a shear flow using the Gaussian beam approximation

2014 ◽  
Vol 759 ◽  
pp. 676-700 ◽  
Author(s):  
C. Rodas ◽  
M. Pulido
Keyword(s):  
Shear Flow ◽  
Gaussian Beam ◽  
Ray Tracing ◽  
Gravity Waves ◽  
Convective Instability ◽  
Shear Flows ◽  
Computational Cost ◽  
Dynamical Instability ◽  
Initial Time ◽  
Instability Criterion

AbstractThe propagation of transient inertio-gravity waves in a shear flow is examined using the Gaussian beam formulation. This formulation assumes Gaussian wavepackets in the spectral space and uses a second-order Taylor expansion of the phase of the wave field. In this sense, the Gaussian beam formulation is also an asymptotic approximation like spatial ray tracing; however, the first one is free of the singularities found in spatial ray tracing at caustics. Therefore, the Gaussian beam formulation permits the examination of the evolution of transient inertio-gravity wavepackets from the initial time up to the destabilization of the flow close to the critical levels. We show that the transience favours the development of the dynamical instability relative to the convective instability. In particular, there is a well-defined threshold for which small initial amplitude transient inertio-gravity waves never reach the convective instability criterion. This threshold does not exist for steady-state inertio-gravity waves for which the wave amplitude increases indefinitely towards the critical level. The Gaussian beam formulation is shown to be a powerful tool to treat analytically several aspects of inertio-gravity waves in simple shear flows. In more realistic shear flows, its numerical implementation is readily available and the required numerical calculations have a low computational cost.

A Parametrization for Triad Interactions of Internal Gravity Waves in Varying Background Flows for WKBJ Ray-Tracing Methods

2020 ◽  
Author(s):  
Georg Sebastian Voelker ◽  
Triantaphyllos Akylas ◽  
Ulrich Achatz
Keyword(s):  
Ray Tracing ◽  
Gravity Waves ◽  
Energy Transport ◽  
Multiple Scale ◽  
Internal Gravity Waves ◽  
Quantitative Agreement ◽  
Mean Flow ◽  
Wave Trains ◽  
The Impact ◽  
Triad Interactions

<p>Internal gravity waves are a well known mechanism of energy transport in stratified fluids such as the atmosphere and the ocean. Their abundance and importance for various geophysical processes like ocean mixing and momentum deposition in atmospheric jets are widely accepted. While resonant wave-wave interactions of monochromatic disturbances have received intensive study, little work has been done on triad interactions between wave trains that are modulated by a variable mean flow.</p><p>Using the method of multiple scale asymptotics we consider a weakly non-linear Boussinesq WKBJ theory for interacting gravity wave trains propagating through a finite amplitude background flow. Consequently the wave trains are allowed to spectrally pass through resonance conditions and exchange energy when sufficiently close to resonance. We find a global optimal threshold for the deviation from resonance and derive a corresponding parametrization for the triad interaction applicable to ray tracing schemes.</p><p>We test the theory with idealized simulations in which two wave trains generate a third by passing through resonance in a sinusoidal background shear flow with varying vertical scales. Comparing WKBJ simulations with wave resolving large eddy simulations we find qualitative and quantitative agreement. Furthermore we assess the impact of the strength of the modulation as well as the effect of the wave amplitudes on the energy exchange between the interacting wave triad.</p>

scholarly journals Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

2015 ◽  
Vol 15 (5) ◽  
pp. 2709-2721 ◽  
Author(s):  
M. Pramitha ◽  
M. Venkat Ratnam ◽  
A. Taori ◽  
B. V. Krishna Murthy ◽  
D. Pallamraju ◽  
...  
Keyword(s):  
Ray Tracing ◽  
Gravity Waves ◽  
High Frequency ◽  
Phase Speed ◽  
Horizontal Wind ◽  
Climatological Model ◽  
Background Temperature ◽  
The Waves ◽  
High Phase ◽  
Mf Radar

Abstract. Sources and propagation characteristics of high-frequency gravity waves observed in the mesosphere using airglow emissions from Gadanki (13.5° N, 79.2° E) and Hyderabad (17.5° N, 78.5° E) are investigated using reverse ray tracing. Wave amplitudes are also traced back, including both radiative and diffusive damping. The ray tracing is performed using background temperature and wind data obtained from the MSISE-90 and HWM-07 models, respectively. For the Gadanki region, the suitability of these models is tested. Further, a climatological model of the background atmosphere for the Gadanki region has been developed using nearly 30 years of observations available from a variety of ground-based (MST radar, radiosondes, MF radar) and rocket- and satellite-borne measurements. ERA-Interim products are utilized for constructing background parameters corresponding to the meteorological conditions of the observations. With the reverse ray-tracing method, the source locations for nine wave events could be identified to be in the upper troposphere, whereas for five other events the waves terminated in the mesosphere itself. Uncertainty in locating the terminal points of wave events in the horizontal direction is estimated to be within 50–100 km and 150–300 km for Gadanki and Hyderabad wave events, respectively. This uncertainty arises mainly due to non-consideration of the day-to-day variability in the tidal amplitudes. Prevailing conditions at the terminal points for each of the 14 events are provided. As no convection in and around the terminal points is noticed, convection is unlikely to be the source. Interestingly, large (~9 m s−1km−1) vertical shears in the horizontal wind are noticed near the ray terminal points (at 10–12 km altitude) and are thus identified to be the source for generating the observed high-phase-speed, high-frequency gravity waves.

Gravity Wave identification using GPS Total Electron Content in South East Asia

2020 ◽  
Author(s):  
Sarthak Srivastava ◽  
Amal Chandran
Keyword(s):  
East Asia ◽  
Ray Tracing ◽  
Gravity Wave ◽  
Total Electron Content ◽  
Gravity Waves ◽  
Electron Content ◽  
South East Asia ◽  
Total Electron ◽  
Convective Clouds ◽  
Deep Convective Clouds

<p>Ionospheric Total Electron Content (TEC) data from ground-based Global Positioning System (GPS) receiver networks have been used previously to detect Travelling Ionospheric Disturbances (TIDs). The TIDs have been shown to arise through coupling of lower atmosphere with the Ionosphere with Gravity Waves as the coupling mechanism. Gravity Waves generated by earthquakes, tsunamis, volcanoes, topography, convection and even solar eclipses have been detected using GPS TEC data. In this study, we identify Gravity Wave signatures in GPS TEC data derived from the Sumatran GPS Array (SuGAr) network. SuGAr is a network of 49 ground-based GPS stations along the convergent plate boundary between Indo-Australian and Asian tectonic plates in western Sumatra, Indonesia. Since initiation in 2002, data from SuGAr has primarily been used to study earthquakes and plate-tectonics in south-east Asia. Due to its location along the seismically-active region, SuGAr can provide valuable data for studying co-seismic Gravity Waves triggered by terrestrial-atmosphere coupling. Frequent occurrence of deep convective clouds in tropical region implies that SuGAr data also provides a unique opportunity to study atmospheric waves generated by convection. </p><p>We have identified Gravity Waves across a wide spectrum corresponding to seismic and tropical convection events in Sumatran region. Upon identifying the wave signatures, we characterized the wave parameters and identified the wave sources through suitable ray tracing calculations. In this paper we show acoustic-gravity waves generated by the 2012 Sumatra great earthquake sequence consisting of 2 largest strike slip earthquakes ever recorded. Spectral analysis indicates the presence of fundamental resonant frequencies for solid Earth-atmosphere coupling. Using a geometric ray tracing method, we also trace the waves very close to the reported epicentres of the double earthquake sequence. We also discuss inertia-gravity waves generated due to convection in South-East Asia using SuGAr TEC data for 2018. Indication of deep convective clouds is confirmed through satellite-based cloud top brightness temperature data.  Ray tracing is performed to further trace the observed waves to the convective system location.</p>

Generation and Propagation of Inertia–Gravity Waves from Vortex Dipoles and Jets

2009 ◽  
Vol 66 (5) ◽  
pp. 1294-1314 ◽  
Author(s):  
Shuguang Wang ◽  
Fuqing Zhang ◽  
Chris Snyder
Keyword(s):  
Ray Tracing ◽  
Gravity Waves ◽  
Mesoscale Model ◽  
Rossby Number ◽  
Small Range ◽  
Grid Spacing ◽  
Coriolis Parameter ◽  
Vortex Dipoles ◽  
Horizontal Variations ◽  
Inertia Gravity Waves

Abstract This study investigates gravity wave generation and propagation from jets within idealized vortex dipoles using a nonhydrostatic mesoscale model. Two types of initially balanced and localized jets induced by vortex dipoles are examined here. These jets have their maximum strength either at the surface or in the middle levels of a uniformly stratified atmosphere. Within these dipoles, inertia–gravity waves with intrinsic frequencies 1–2 times the Coriolis parameter are simulated in the jet exit region. These gravity waves are nearly phase locked with the jets as shown in previous studies, suggesting spontaneous emission of the waves by the localized jets. A ray tracing technique is further employed to investigate the propagation effects of gravity waves. The ray tracing analysis reveals strong variation of wave characteristics along ray paths due to variations (particularly horizontal variations) in the propagating environment. The dependence of wave amplitude on the jet strength (and thus on the Rossby number of the flow) is examined through experiments in which the two vortices are initially separated by a large distance but subsequently approach each other and form a vortex dipole with an associated amplifying localized jet. The amplitude of the stationary gravity waves in the simulations with 90-km grid spacing increases as the square of the Rossby number (Ro), when Ro falls in a small range of 0.05–0.15, but does so significantly more rapidly when a smaller grid spacing is used.

scholarly journals Investigation of sources of gravity waves observed in the Brazilian Equatorial region on 08 April 2005

2019 ◽  
Author(s):  
Oluwakemi Dare-Idowu ◽  
Igo Paulino ◽  
Cosme A. O. B. Figueiredo ◽  
Amauri F. Medeiros ◽  
Ricardo A. Buriti ◽  
...  
Keyword(s):  
Ray Tracing ◽  
Gravity Waves ◽  
Spectral Characteristics ◽  
Phase Speed ◽  
Radar Data ◽  
Equatorial Region ◽  
Inter Tropical Convergence Zone ◽  
Wind Profiles ◽  
Ray Path ◽  
The Waves

Abstract. On 08 April 2005, a strong gravity wave activity (more than 3 hours) was observed in São João do Cariri (7.4° S, 36.5° W). These waves propagated to the southeast and presented different spectral characteristics (wavelength, period and phase speed). Using OH airglow images, the parameters of 5 observed gravity waves were calculated; the wavelengths ranged from ~ 90 to 150 km, the periods from ~ 26 to 67 min and the phase speeds from 32 to 71 m/s. A reserve ray-tracing analysis was performed to investigate the likely sources of these waves. The ray-tracing database was composed of temperature profiles from NRLMSISE-00 model and SABER measurements and wind profiles from HWM-14 model and meteor radar data. According to the ray path, the likely source of these gravity waves was the Inter Tropical Convergence Zone with intense convective processes taking place in the northern part of the observatory. Also, the observed preferential propagation direction of the waves to the southeast could be explained using blocking diagrams, i.e., due to the wind filtering process.

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