scholarly journals On the distortions in calculated GW parameters during slanted atmospheric soundings

2017 ◽  
Author(s):  
Alejandro de la Torre ◽  
Peter Alexander ◽  
Torsten Schmidt ◽  
Pablo Llamedo ◽  
Rodrigo Hierro
Keyword(s):  
Aspect Ratio ◽  
Gravity Waves ◽  
Momentum Flux ◽  
Elevation Angle ◽  
Vertical Flux ◽  
Temperature Profiles ◽  
Model Simulations ◽  
Horizontal Momentum ◽  
Two Parameters ◽  
Atmospheric Gravity

Abstract. The significant distortions introduced in the measured atmospheric gravity wavelengths by soundings other than in vertical and horizontal directions, are discussed as a function of elevation angle of the sounding path and the gravity waves aspect ratio. Under- or overestimation of real vertical wavelengths during the measurement process depends basically on the value of these two parameters. The consequences of these distortions on the calculation of the energy and vertical flux of horizontal momentum are analyzed and discussed in the context of two experimental limb satellite setups: GPS-LEO radio occultations and TIMED/SABER measurements. Possible discrepancies previously found between the momentum flux calculated from satellite temperature profiles, on site and from model simulations, may, to a certain degree, be attributed to these distortions. A recalculation of previous momentum flux climatologies based on these considerations seems to be a difficult goal.

scholarly journals On the distortions in calculated GW parameters during slanted atmospheric soundings

2018 ◽  
Vol 11 (3) ◽  
pp. 1363-1375 ◽  
Author(s):  
Alejandro de la Torre ◽  
Peter Alexander ◽  
Torsten Schmidt ◽  
Pablo Llamedo ◽  
Rodrigo Hierro
Keyword(s):  
Aspect Ratio ◽  
Gravity Wave ◽  
Momentum Flux ◽  
Elevation Angle ◽  
Temperature Profiles ◽  
Model Simulations ◽  
Broadband Emission ◽  
Horizontal Momentum ◽  
Two Parameters ◽  
Atmospheric Gravity

Abstract. The significant distortions introduced in the measured atmospheric gravity wavelengths by soundings other than those in vertical and horizontal directions, are discussed as a function of the elevation angle of the sounding path and the gravity wave aspect ratio. Under- or overestimation of real vertical wavelengths during the measurement process depends on the value of these two parameters. The consequences of these distortions on the calculation of the energy and the vertical flux of horizontal momentum are analyzed and discussed in the context of two experimental limb satellite setups: GPS-LEO radio occultations and TIMED/SABER ((Atmosphere using Broadband Emission Radiometry/Thermosphere–Ionosphere–Mesosphere–Energetics and Dynamics)) measurements. Possible discrepancies previously found between the momentum flux calculated from satellite temperature profiles, on site and from model simulations, may to a certain degree be attributed to these distortions. A recalculation of previous momentum flux climatologies based on these considerations seems to be a difficult goal.

scholarly journals Regional variations of mesospheric gravity-wave momentum flux over Antarctica

2006 ◽  
Vol 24 (1) ◽  
pp. 81-88 ◽  
Author(s):  
P. J. Espy ◽  
R. E. Hibbins ◽  
G. R. Swenson ◽  
J. Tang ◽  
M. J. Taylor ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Momentum Flux ◽  
Cross Correlation ◽  
Polar Vortex ◽  
Correlation Coefficients ◽  
Vertical Flux ◽  
Horizontal Wind ◽  
Wave Source ◽  
Horizontal Momentum

Abstract. Images of mesospheric airglow and radar-wind measurements have been combined to estimate the difference in the vertical flux of horizontal momentum carried by high-frequency gravity waves over two dissimilar Antarctic stations. Rothera (67° S, 68° W) is situated in the mountains of the Peninsula near the edge of the wintertime polar vortex. In contrast, Halley (76° S, 27° W), some 1658 km to the southeast, is located on an ice sheet at the edge of the Antarctic Plateau and deep within the polar vortex during winter. The cross-correlation coefficients between the vertical and horizontal wind perturbations were calculated from sodium (Na) airglow imager data collected during the austral winter seasons of 2002 and 2003 at Rothera for comparison with the 2000 and 2001 results from Halley reported previously (Espy et al., 2004). These cross-correlation coefficients were combined with wind-velocity variances from coincident radar measurements to estimate the daily averaged upper-limit of the vertical flux of horizontal momentum due to gravity waves near the peak emission altitude of the Na nightglow layer, 90km. The resulting momentum flux at both stations displayed a large day-to-day variability and showed a marked seasonal rotation from the northwest to the southwest throughout the winter. However, the magnitude of the flux at Rothera was about 4 times larger than that at Halley, suggesting that the differences in the gravity-wave source functions and filtering by the underlying winds at the two stations create significant regional differences in wave forcing on the scale of the station separation.

Asymptotic stability of a polar vortex perturbed by harmonic waves describing atmospheric gravity waves circulating in an equatorial plane of a spherical planet

2018 ◽  
Vol 13 (4) ◽  
pp. 36
Author(s):  
Ranis Ibragimov ◽  
Pirooz Mohazzabi ◽  
Rebecca Roembke ◽  
Justin Van Ee
Keyword(s):  
Shallow Water ◽  
Gravity Waves ◽  
Equatorial Plane ◽  
Polar Vortex ◽  
Water Model ◽  
Large Radius ◽  
Atmospheric Gravity Waves ◽  
Nonstationary Motion ◽  
Two Parameters ◽  
Atmospheric Gravity

We examine stability of the vortex that represents one particular class of exact solution of a a nonlinear shallow water model describing atmospheric gravity waves circulating in an equatorial plane of a spherical planet. The mathematical model is represented by a two-dimensional free boundary Cauchy–Poisson problem on the nonstationary motion of a perfect uid around a solid circle with a sufficiently large radius so that the gravity is directed to the center of the circle. It is shown that the model admits two functionally independent nonlinear systems of shallow water equations. Two essential parameters that control stability of the vortex for both systems are identified. The order of their importance is analyzed and it is shown that one of the systems is more resistant to small perturbations and remains stable for larger range of these two parameters.

scholarly journals The response of super pressure balloons to gravity wave motions

2013 ◽  
Vol 6 (6) ◽  
pp. 10797-10832
Author(s):  
R. A. Vincent ◽  
A. Hertzog
Keyword(s):  
Gravity Waves ◽  
Momentum Flux ◽  
Good Accuracy ◽  
Phase Speed ◽  
Constant Density ◽  
Intrinsic Frequency ◽  
High Frequencies ◽  
Vertical Displacements ◽  
Atmospheric Gravity ◽  
The Antarctic

Abstract. Super pressure balloons (SPB), which float on constant density (isopycnic) surfaces, provide a unique way of measuring the properties of atmospheric gravity waves (GW) as a function of wave intrinsic frequency. Here we devise a quasi-analytic method of investigating the SPB response to GW motions. It is shown that the results agree well with more rigorous numerical simulations of balloon motions and provide a better understanding of the response of SPB to GW, especially at high frequencies. The methodology is applied to ascertain the accuracy of GW studies using 12 m diameter SPB deployed in the 2010 Concordiasi campaign in the Antarctic. In comparison with the situation in earlier campaigns, the vertical displacements of the SPB were measured directly using GPS. It is shown using a large number of Monte-Carlo type simulations with realistic instrumental noise that important wave parameters, such as momentum flux, phase speed and wavelengths, can be retrieved with good accuracy from SPB observations for intrinsic wave periods greater than about 10 min. The noise floor for momentum flux is estimated to be about 10−4 mPa.

scholarly journals A new approach to global gravity wave momentum flux determination from GPS radio occultation data

2013 ◽  
Vol 6 (2) ◽  
pp. 2907-2933 ◽  
Author(s):  
A. Faber ◽  
P. Llamedo ◽  
T. Schmidt ◽  
A. de la Torre ◽  
J. Wickert
Keyword(s):  
Gravity Wave ◽  
Radio Occultation ◽  
Vertical Flux ◽  
Spatial Distance ◽  
Temperature Structure ◽  
Temperature Profiles ◽  
Gps Radio Occultation ◽  
Global Gravity ◽  
Horizontal Momentum

Abstract. GPS Radio Occultation (RO) is a well-established technique for obtaining global gravity wave (GW) information. RO uses GPS signals received aboard low Earth orbiting satellites for atmospheric limb sounding. Temperature profiles are derived with high vertical resolution and provide a global coverage under any weather conditions offering the possibility for global monitoring of the vertical temperature structure and atmospheric wave parameters. The six satellites constellation COSMIC/FORMOSAT-3 delivers approximately 2000 temperature profiles daily. In this study, we use a method to obtain global distributions of horizontal gravity wave wavelengths, to be applied in the determination of the vertical flux of horizontal momentum transported by gravity waves. The horizontal wavenumber is derived by the ratio of the phase shift and the spatial distance between adjacent temperature fluctuation profiles at a given altitude, following the method by Ern et al. (2004). A new method for the determination of the real horizontal wavelength from triads of vertical profiles is presented and applied to the COSMIC data. The horizontal and vertical wavelength, the specific potential energy (Ep) and the vertical flux of horizontal momentum (MF) are calculated and their global distribution is discussed.

scholarly journals On the determination of gravity wave momentum flux from GPS radio occultation data

2013 ◽  
Vol 6 (11) ◽  
pp. 3169-3180 ◽  
Author(s):  
A. Faber ◽  
P. Llamedo ◽  
T. Schmidt ◽  
A. de la Torre ◽  
J. Wickert
Keyword(s):  
Gravity Wave ◽  
Radio Occultation ◽  
Weather Conditions ◽  
Vertical Flux ◽  
Temperature Structure ◽  
Temperature Profiles ◽  
Gps Radio Occultation ◽  
Horizontal Momentum ◽  
Occultation Data

Abstract. Global Positioning System (GPS) radio occultation (RO) is a well-established technique for obtaining global gravity wave (GW) information. RO uses GPS signals received by low Earth-orbiting satellites for atmospheric limb sounding. Temperature profiles are derived with high vertical resolution and provide a global coverage under any weather conditions, offering the possibility of global monitoring of the vertical temperature structure and atmospheric wave parameters. The six-satellite constellation COSMIC/FORMOSAT-3 delivers approximately 2000 temperature profiles daily. In this study, we use a method to obtain global distributions of horizontal gravity wave wavelengths, to be applied in the determination of the vertical flux of horizontal momentum transported by gravity waves. Here, a method for the determination of the real horizontal wavelength from three vertical profiles is applied to the COSMIC data. The horizontal and vertical wavelength, the specific potential energy (Ep), and the vertical flux of horizontal momentum (MF) are calculated and their global distribution is discussed.

scholarly journals The response of superpressure balloons to gravity wave motions

2014 ◽  
Vol 7 (4) ◽  
pp. 1043-1055 ◽  
Author(s):  
R. A. Vincent ◽  
A. Hertzog
Keyword(s):  
Gravity Waves ◽  
Momentum Flux ◽  
Good Accuracy ◽  
Phase Speed ◽  
Constant Density ◽  
Intrinsic Frequency ◽  
High Frequencies ◽  
Vertical Displacements ◽  
Atmospheric Gravity ◽  
The Antarctic

Abstract. Superpressure balloons (SPB), which float on constant density (isopycnic) surfaces, provide a unique way of measuring the properties of atmospheric gravity waves (GW) as a function of wave intrinsic frequency. Here we devise a quasi-analytic method of investigating the SPB response to GW motions. It is shown that the results agree well with more rigorous numerical simulations of balloon motions and provide a better understanding of the response of SPB to GW, especially at high frequencies. The methodology is applied to ascertain the accuracy of GW studies using 12 m diameter SPB deployed in the 2010 Concordiasi campaign in the Antarctic. In comparison with the situation in earlier campaigns, the vertical displacements of the SPB were measured directly using GPS. It is shown using a large number of Monte Carlo-type simulations with realistic instrumental noise that important wave parameters, such as momentum flux, phase speed and wavelengths, can be retrieved with good accuracy from SPB observations for intrinsic wave periods greater than ca. 10 min. The noise floor for momentum flux is estimated to be ca. 10−4 mPa.

Wavelet analysis of gravity waves on Venus using radio occultation temperature profiles

2020 ◽  
Author(s):  
Takeshi Imamura ◽  
Ryota Mori ◽  
Hiroki Ando ◽  
Javier Peralta ◽  
Bernd Häusler ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Radio Occultation ◽  
Wave Packets ◽  
Statistical Characteristics ◽  
Temperature Profiles ◽  
Vertical Wavelength ◽  
Individual Wave ◽  
High Vertical Resolution ◽  
Atmospheric Gravity ◽  
The Waves

<p>Atmospheric gravity waves are thought to play crucial roles in transporting momentum and energy in planetary atmospheres. They are frequently observed as localized quasi-monochromatic wave packets in cloud images, while the vertical structures of the wave packets have not been investigated. The wavelengths and the packet lengths should reflect the generation processes of the respective wave packets. Though wave packets are thought to propagate independently, they are superposed on each other to induce an unstable field. The statistical characteristics of wave packets need to be known to understand the roles of the waves in the development of the atmospheric structure.<br /> We study the characteristics of gravity wave packets in Venus’s atmosphere using high vertical resolution temperature profiles obtained by Venus Express and Akatsuki radio occultation experiments with radio holographic methods (Imamura et al. 2018). Localized disturbances are extracted by applying wavelet transform to the vertical temperature distributions. The analysis showed that (1) wave packets having different wavelengths are overlapped with each other, (2) each wave packet typically includes <3 cycles, (3) waves with vertical wavelengths of ~1 km are frequently seen,(4) individual wave packets are hardly saturating in isolation, while saturation occurs as a result of superposition of wave packets, and (4) short-vertical wavelength waves are more frequently observed at lower altitudes.</p>

Some Effects of Model Resolution on Simulated Gravity Waves Generated by Deep, Mesoscale Convection

2005 ◽  
Vol 62 (9) ◽  
pp. 3408-3419 ◽  
Author(s):  
Todd P. Lane ◽  
Jason C. Knievel
Keyword(s):  
Gravity Waves ◽  
Horizontal Resolution ◽  
Vertical Flux ◽  
Model Resolution ◽  
Convective Clouds ◽  
The Past ◽  
Deep Convective Clouds ◽  
Horizontal Momentum ◽  
Vertically Propagating ◽  
Horizontal Grid

Abstract Over the past decade, numerous numerical modeling studies have shown that deep convective clouds can produce gravity waves that induce a significant vertical flux of horizontal momentum. Such studies used models with horizontal grid spacings of O(1 km) and produced strong gravity waves with horizontal wavelengths greater than about 20 km. This paper is an examination of how simulated gravity waves and their momentum flux are sensitive to model resolution. It is shown that increases in horizontal resolution produce more power in waves with shorter horizontal wavelengths. This change in the gravity waves’ spectra influences their vertical propagation. In some cases, gravity waves that were vertically propagating in coarse simulations become vertically trapped in fine simulations, which strongly influences the vertical flux of horizontal momentum.

Lidar measurements of the middle atmosphere

1991 ◽  
Vol 69 (8-9) ◽  
pp. 1076-1086 ◽  
Author(s):  
A. I. Carswell ◽  
S. R. Pal ◽  
W. Steinbrecht ◽  
J. A. Whiteway ◽  
A. Ulitsky ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Middle Atmosphere ◽  
Temperature Profiles ◽  
Atmospheric Measurements ◽  
Atmospheric Gravity Waves ◽  
Lidar Measurements ◽  
Atmospheric Gravity ◽  
Stratospheric Aerosols

This paper describes a new lidar facility that has been established for atmospheric measurements from the ground up to ~90 km altitude. Measurements of stratospheric aerosols and ozone are presented, and density and temperature profiles into the mesosphere are analyzed to derive information about atmospheric gravity waves.

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