Internal Gravity Wave Emission in Different Dynamical Regimes

AbstractWe aim to diagnose internal gravity waves emitted from balanced flow and investigate their role in the downscale transfer of energy. We use an idealized numerical model to simulate a range of baroclinically unstable flows to mimic dynamical regimes ranging from ageostrophic to quasigeostrophic flows. Wavelike signals present in the simulated flows, seen for instance in the vertical velocity, can be related to gravity wave activity identified by frequency and frequency–wavenumber spectra. To explicitly assign the energy contributions to the balanced and unbalanced (gravity) modes, we perform linear and nonlinear modal decomposition to decompose the full state variable into its balanced and unbalanced counterparts. The linear decomposition shows a reasonable separation of the slow and fast modes but is no longer valid when applied to a nonlinear system. To account for the nonlinearity in our system, we apply the normal mode initialization technique proposed by Machenhauer in 1977. Further, we assess the strength of the gravity wave activity and dissipation related to the decomposed modes for different dynamical regimes. We find that gravity wave emission becomes increasingly stronger going from quasigeostrophic to ageostrophic regime. The kinetic energy tied to the unbalanced mode scales close to Ro2 (or Ri−1), with Ro and Ri being the Rossby and Richardson numbers, respectively. Furthermore, internal gravity waves dissipate predominantly through small-scale dissipation, which emphasizes their role in the downscale energy transfer.

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Spatial and temporal analysis of high-frequency internal gravity wave signatures in brightness temperature satellite images

10.5194/egusphere-egu21-1609 ◽

2021 ◽

Author(s):

Robert Vicari

Keyword(s):

Water Vapor ◽

Brightness Temperature ◽

Gravity Wave ◽

Gravity Waves ◽

High Frequency ◽

Satellite Images ◽

Internal Gravity Wave ◽

Internal Gravity Waves ◽

Small Scale ◽

Wave Patterns

Highly idealized model studies suggest that convectively generated internal gravity waves in the troposphere with horizontal wavelengths on the order of a few kilometers may affect the lifetime, spacing, and depth of clouds and convection. To answer whether such a convection-wave coupling occurs in the real atmosphere, one needs to find corresponding events in observations. In general, the study of high-frequency internal gravity wave-related phenomena in the troposphere is a challenging task because they are usually small-scale and intermittent. To overcome case-by-case studies, it is desirable to have an automatic method to analyze as much data as possible and provide enough independent and diverse evidence. Here, we focus on brightness temperature satellite images, in particular so-called satellite water vapor channels. These channels measure the radiation at wavelengths corresponding to the energy emitted by water vapor and provide cloud-independent observations of internal gravity waves, in contrast to visible and other infrared satellite channels where one relies on the wave impacts on clouds. In addition, since these water vapor channels are sensitive to certain vertical layers in the troposphere, combining the images also reveals some vertical structure of the observed waves. We propose an algorithm based on local Fourier analyses to extract information about high-frequency wave patterns in given brightness temperature images. This method allows automatic detection and analysis of many wave patterns in a given domain at once, resulting in a climatology that provides an initial observational basis for further research. Using data from the instrument ABI on board the satellite GOES-16 during the field campaign EUREC4A, we demonstrate the capabilities and limitations of the method. Furthermore, we present the respective climatology of the detected waves and discuss approaches based on this to address the initial question.

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Gravity Wave Emission by Shear Instability

Journal of Physical Oceanography ◽

10.1175/jpo-d-19-0029.1 ◽

2019 ◽

Vol 49 (9) ◽

pp. 2393-2406 ◽

Cited By ~ 1

Author(s):

Carsten Eden ◽

Manita Chouksey ◽

Dirk Olbers

Keyword(s):

Gravity Wave ◽

Single Layer ◽

Internal Gravity Waves ◽

Shear Instability ◽

Vertical Shear ◽

Wave Signal ◽

Wave Emission ◽

Balanced Flow ◽

Single Layer Model

AbstractGravity wave emission by geostrophically balanced flow is diagnosed in numerical simulations of lateral and vertical shear instabilities. The diagnostic method in use allows for a separation of balanced flow and residual wave signal up to fourth order in the Rossby number (Ro). While evidence is found for a small but finite gravity wave emission from balanced flow in a single-layer model with large lateral shear and large Ro, a vertically resolved model with moderate velocity amplitudes appropriate to the interior ocean hardly shows any wave emission. Only when static instabilities generated by the shear instability of the balanced flow are allowed can a gravity wave signal similar to the ones reported in earlier studies be detected in the vertically resolved case. This result suggests a relatively small role of spontaneous wave emission in the classical sense of Lighthill radiation, and emphasizes the role of convective or symmetric instabilities during frontogenesis for the generation of internal gravity waves in the ocean and atmosphere.

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Linear mechanism by which internal gravity waves are generated and intensified in the ionosphere when interacting with an inhomogeneous zonal wind: 2. Internal gravity wave generation and intensification during the linear evolution stage

Geomagnetism and Aeronomy ◽

10.1134/s0016793213040026 ◽

2013 ◽

Vol 53 (4) ◽

pp. 471-478 ◽

Cited By ~ 2

Author(s):

G. D. Aburdzhaniya ◽

O. A. Kharshiladze ◽

Kh. Z. Chargaziya

Keyword(s):

Gravity Wave ◽

Gravity Waves ◽

Zonal Wind ◽

Internal Gravity Wave ◽

Internal Gravity Waves ◽

Wave Generation ◽

Linear Evolution ◽

Evolution Stage

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Stratospheric gravity waves at Southern Hemisphere orographic hotspots: 2003–2014 AIRS/Aqua observations

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-9381-2016 ◽

2016 ◽

Vol 16 (14) ◽

pp. 9381-9397 ◽

Cited By ~ 30

Author(s):

Lars Hoffmann ◽

Alison W. Grimsdell ◽

M. Joan Alexander

Keyword(s):

Gravity Wave ◽

Southern Hemisphere ◽

Antarctic Peninsula ◽

Gravity Waves ◽

General Circulation ◽

Wave Activity ◽

Small Scale ◽

Mountain Wave ◽

Kerguelen Islands ◽

The Antarctic

Abstract. Stratospheric gravity waves from small-scale orographic sources are currently not well-represented in general circulation models. This may be a reason why many simulations have difficulty reproducing the dynamical behavior of the Southern Hemisphere polar vortex in a realistic manner. Here we discuss a 12-year record (2003–2014) of stratospheric gravity wave activity at Southern Hemisphere orographic hotspots as observed by the Atmospheric InfraRed Sounder (AIRS) aboard the National Aeronautics and Space Administration's (NASA) Aqua satellite. We introduce a simple and effective approach, referred to as the “two-box method”, to detect gravity wave activity from infrared nadir sounder measurements and to discriminate between gravity waves from orographic and other sources. From austral mid-fall to mid-spring (April–October) the contributions of orographic sources to the observed gravity wave occurrence frequencies were found to be largest for the Andes (90 %), followed by the Antarctic Peninsula (76 %), Kerguelen Islands (73 %), Tasmania (70 %), New Zealand (67 %), Heard Island (60 %), and other hotspots (24–54 %). Mountain wave activity was found to be closely correlated with peak terrain altitudes, and with zonal winds in the lower troposphere and mid-stratosphere. We propose a simple model to predict the occurrence of mountain wave events in the AIRS observations using zonal wind thresholds at 3 and 750 hPa. The model has significant predictive skill for hotspots where gravity wave activity is primarily due to orographic sources. It typically reproduces seasonal variations of the mountain wave occurrence frequencies at the Antarctic Peninsula and Kerguelen Islands from near zero to over 60 % with mean absolute errors of 4–5 percentage points. The prediction model can be used to disentangle upper level wind effects on observed occurrence frequencies from low-level source and other influences. The data and methods presented here can help to identify interesting case studies in the vast amount of AIRS data, which could then be further explored to study the specific characteristics of stratospheric gravity waves from orographic sources and to support model validation.

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Analysis of internal gravity waves with GPS RO density profiles

Atmospheric Measurement Techniques ◽

10.5194/amt-7-4123-2014 ◽

2014 ◽

Vol 7 (12) ◽

pp. 4123-4132 ◽

Cited By ~ 10

Author(s):

P. Šácha ◽

U. Foelsche ◽

P. Pišoft

Keyword(s):

Gravity Wave ◽

Gravity Waves ◽

Internal Gravity Wave ◽

Internal Gravity Waves ◽

Atmospheric Density ◽

Retrieval Process ◽

Density Profiles ◽

Height Range ◽

Upper Troposphere ◽

The Past

Abstract. GPS radio occultation (RO) data have proved to be a great tool for atmospheric monitoring and studies. In the past decade, they were frequently used for analyses of the internal gravity waves in the upper troposphere and lower stratosphere region. Atmospheric density is the first quantity of state gained in the retrieval process and is not burdened by additional assumptions. However, there are no studies elaborating in detail the utilization of GPS RO density profiles for gravity wave analyses. In this paper, we introduce a method for density background separation and a methodology for internal gravity wave analysis using the density profiles. Various background choices are discussed and the correspondence between analytical forms of the density and temperature background profiles is examined. In the stratosphere, a comparison between the power spectrum of normalized density and normalized dry temperature fluctuations confirms the suitability of the density profiles' utilization. In the height range of 8–40 km, results of the continuous wavelet transform are presented and discussed. Finally, the limits of our approach are discussed and the advantages of the density usage are listed.

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On strongly nonlinear gravity waves in a vertically sheared atmosphere

10.5194/egusphere-egu21-4878 ◽

2021 ◽

Author(s):

Georg Sebastian Voelker ◽

Mark Schlutow

Keyword(s):

Gravity Wave ◽

Gravity Waves ◽

Internal Gravity Wave ◽

Internal Gravity Waves ◽

Wave Drag ◽

Mean Flow ◽

Flow Strength ◽

Weakly Nonlinear ◽

Strongly Nonlinear ◽

The Mean

Internal gravity waves are a well-known mechanism of energy redistribution in stratified fluids such as the atmosphere. They may propagate from their generation region, typically in the Troposphere, up to high altitudes. During their lifetime internal waves couple to the atmospheric background through various processes. Among the most important interactions are the exertion of wave drag on the horizontal mean-flow, the heat generation upon wave breaking, or the mixing of atmospheric tracers such as aerosols or greenhouse gases.Many of the known internal gravity wave properties and interactions are covered by linear or weakly nonlinear theories. However, for the consideration of some of the crucial effects, like a reciprocal wave-mean-flow interaction including the exertion of wave drag on the mean-flow, strongly nonlinear systems are required. That is, there is no assumption on the wave amplitude relative to the mean-flow strength such that they may be of the same order.Here, we exploit a strongly nonlinear Boussinesq theory to analyze the stability of a stationary internal gravity wave which is refracted at the vertical edge of a horizontal jet. Thereby we assume that the incident wave is horizontally periodic, non-hydrostatic, and vertically modulated. Performing a linear stability analysis in the vicinity of the jet edge we find necessary and sufficient criteria for instabilities to grow. In particular, the refracted wave becomes unstable if its incident amplitude is large enough and both mean-flow horizontal winds, below and above the edge of the jet, do not exceed particular upper bounds.

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Comparison between seasonal variations in tidal and internal gravity wave activity as derived from observations at Maimaga and Tiksi

Solnechno-Zemnaya Fizika ◽

10.12737/szf-42201811 ◽

2018 ◽

Vol 4 (2) ◽

pp. 109-115

Author(s):

Вера Сивцева ◽

Vera Sivtseva ◽

Петр Аммосов ◽

Petr Ammosov ◽

Галина Гаврильева ◽

...

Keyword(s):

Gravity Waves ◽

Seasonal Variations ◽

Near Infrared ◽

Internal Gravity Wave ◽

Internal Gravity Waves ◽

Infrared Region ◽

Wave Activity ◽

Mean Values ◽

Tidal Waves ◽

Hydroxyl Emission

Since 2015, simultaneous observations of temperature of the high-latitude mesopause (87 km) have been made at Maimaga (63.04° N, 129.51° E) and Tiksi (71.58° N, 128.77° E) stations. These stations record spectra with Shamrock (Andor) photosensitive infrared spectrographs detecting the OH (3, 1) band in the near-infrared region (about 1.5 μm). We analyze temperature data obtained in observation seasons from 2015 to 2017. Standard deviations of temperature σ from its mean values are taken as characteristics of wave activity at night. We have obtained standard temperature deviations corresponding to internal gravity waves (IGW) (σgw) and tidal waves (σtd). Mean night rotational temperatures of hydroxyl emission almost coincide, and seasonal variations of gravity and tidal waves have a similar form during two seasons of simultaneous observations at Tiksi and Maimaga.

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Stratospheric gravity waves at southern hemisphere orographic hotspots: 2003–2014 AIRS/Aqua observations

10.5194/acp-2016-341 ◽

2016 ◽

Author(s):

Lars Hoffmann ◽

Alison W. Grimsdell ◽

M. Joan Alexander

Keyword(s):

Gravity Wave ◽

Southern Hemisphere ◽

Antarctic Peninsula ◽

Gravity Waves ◽

General Circulation ◽

Wave Activity ◽

Small Scale ◽

Mountain Wave ◽

Kerguelen Islands ◽

The Antarctic

Abstract. Stratospheric gravity waves from small-scale orographic sources are currently not well-represented in general circulation models. This may be a reason why many simulations have difficulty reproducing the dynamical behaviour of the southern hemisphere polar vortex in a realistic manner. Here we discuss a 12-year record (2003–2014) of stratospheric gravity wave activity at southern hemisphere orographic hotspots as observed by the Atmospheric InfraRed Sounder (AIRS) aboard the National Aeronautics and Space Administration's (NASA's) Aqua satellite. We introduce a simple and effective approach, referred to as the "two-box method", to detect gravity wave activity from infrared nadir sounder measurements and to discriminate between gravity waves from orographic and other sources. From austral mid fall to mid spring (April–October) the contributions of orographic sources to the observed gravity wave occurrence frequencies were found to be largest for the Andes (90 %), followed by the Antarctic Peninsula (76 %), Kerguelen Islands (73 %), Tasmania (70 %), New Zealand (67 %), Heard Island (60 %), and other hotspots (24–54 %). Mountain wave activity was found to be closely correlated with peak terrain altitudes, and with zonal winds in the lower troposphere and mid stratosphere. We propose a simple model to predict the occurrence of mountain wave events in the AIRS observations using zonal wind thresholds at 3 hPa and 750 hPa. The model has significant predictive skill for hotspots where gravity wave activity is primarily due to orographic sources. It typically reproduces seasonal variations of the mountain wave occurrence frequencies at the Antarctic Peninsula and Kerguelen Islands from near zero to over 60 % with mean absolute errors of 4–5 percentage points. The prediction model can be used to disentangle upper level wind effects on observed occurrence frequencies from low level source and other influences. The data and methods presented here can help to identify interesting case studies in the vast amount of AIRS data, which could then be further explored to study the specific characteristics of stratospheric gravity waves from orographic sources and to support model validation.

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Comparison between seasonal variations in tidal and internal gravity wave activity as derived from observations at Maimaga and Tiksi

Solar-Terrestrial Physics ◽

10.12737/stp-41201811 ◽

2018 ◽

Vol 4 (2) ◽

pp. 69-72 ◽

Cited By ~ 1

Author(s):

Вера Сивцева ◽

Vera Sivtseva ◽

Петр Аммосов ◽

Petr Ammosov ◽

Галина Гаврильева ◽

...

Keyword(s):

Gravity Waves ◽

Seasonal Variations ◽

Near Infrared ◽

Internal Gravity Wave ◽

Internal Gravity Waves ◽

Infrared Region ◽

Wave Activity ◽

Mean Values ◽

Tidal Waves ◽

Hydroxyl Emission

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A microbarograph for internal gravity wave studies in Antarctica

Antarctic Science ◽

10.1017/s0954102092000373 ◽

1992 ◽

Vol 4 (2) ◽

pp. 241-248 ◽

Cited By ~ 11

Author(s):

P.S. Anderson ◽

S.D. Mobbs ◽

J.C. King ◽

I. McConnell ◽

J.M. Rees

Keyword(s):

Gravity Wave ◽

Gravity Waves ◽

Pressure Fluctuations ◽

Internal Gravity Wave ◽

Internal Gravity Waves ◽

Small Pressure ◽

Prototype Instrument ◽

Antarctic Environment

Measurement of pressure fluctuations provides the best means of detecting atmospheric internal gravity waves at the Earth's surface. We have developed an instrument which is sufficiently sensitive to detect the small pressure fluctuations associated with such waves yet robust enough for deployment in an Antarctic environment. The instrument incorporates several novel features, both in its design and in the method of deployment used. A prototype instrument has been successfully deployed at the British Antarctic Survey's Halley Station during 1989. The design of an experiment using an array of six improved instruments is briefly described.

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