Artificial ionospheric wave number 4 structure below the F2 region due to the Abel retrieval of radio occultation measurements

Abstract. GPS radio occultation (RO) is characterized by high accuracy and excellent height resolution, which has great advantages in analyzing atmospheric structures including small-scale vertical fluctuations. The vertical resolution of the geometrical optics (GO) method in the stratosphere is about 1.5 km due to Fresnel radius limitations, but full spectrum inversion (FSI) can provide superior resolutions. We applied FSI to COSMIC GPS-RO profiles from ground level up to 30 km altitude, although basic retrieval at UCAR/CDAAC sets the sewing height from GO to FSI below the tropopause. We validated FSI temperature profiles with routine high-resolution radiosonde data in Malaysia and North America collected within 400 km and about 30 min of the GPS RO events. The average discrepancy at 10–30 km altitude was less than 0.5 K, and the bias was equivalent with the GO results. Using the FSI results, we analyzed the vertical wave number spectrum of normalized temperature fluctuations in the stratosphere at 20–30 km altitude, which exhibits good consistency with the model spectra of saturated gravity waves. We investigated the white noise floor that tends to appear at high wave numbers, and the substantial vertical resolution of the FSI method was estimated as about 100–200 m in the lower stratosphere. We also examined a criterion for the upper limit of the FSI profiles, beyond which bending angle perturbations due to system noises, etc., could exceed atmospheric excess phase fluctuations. We found that the FSI profiles can be used up to about 28 km in studies of temperature fluctuations with vertical wave lengths as short as 0.5 km.

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Analysis of vertical wave number spectrum of atmospheric gravity waves in the stratosphere using COSMIC GPS radio occultation data

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-4-2071-2011 ◽

2011 ◽

Vol 4 (2) ◽

pp. 2071-2097

Author(s):

T. Tsuda ◽

X. Lin ◽

H. Hayashi ◽

Keyword(s):

Gravity Waves ◽

Radio Occultation ◽

Temperature Fluctuations ◽

Ground Level ◽

Wave Number ◽

Radiosonde Data ◽

Small Scale ◽

Vertical Resolution ◽

Full Spectrum ◽

Gps Radio Occultation

Abstract. GPS radio occultation (RO) is characterized by high accuracy and excellent height resolution, which has great advantages in analyzing atmospheric structures including small-scale vertical fluctuations. The vertical resolution of the geometrical optics (GO) method in the stratosphere is about 1.5 km due to Fresnel radius limitations, but full spectrum inversion (FSI) can provide superior resolutions. We applied FSI to COSMIC GPS-RO profiles from ground level up to 30 km altitude, although basic retrieval at UCAR/CDAAC sets the sewing height from GO to FSI below the tropopause. We validated FSI temperature profiles with routine high-resolution radiosonde data in Malaysia and North America collected within 400 km and about 30 min of the GPS RO events. The average discrepancy at 10–30 km altitude was less than 0.5 K, and the bias was equivalent with the GO results. Using the FSI results, we analyzed the vertical wave number spectrum of normalized temperature fluctuations in the stratosphere at 20–30 km altitude, which exhibits good consistency with the model spectra of saturated gravity waves. We investigated the white noise floor that tends to appear at high wave numbers, and the substantial vertical resolution of the FSI method was estimated as about 100–200 m in the lower stratosphere. We also examined a criterion for the upper limit of the FSI profiles, beyond which bending angle perturbations due to system noises, etc, could exceed atmospheric excess phase fluctuations. We found that the FSI profiles can be used up to about 28 km in studies of temperature fluctuations with vertical wave lengths as short as 0.5 km.

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Observation and a numerical study of gravity waves during tropical cyclone Ivan (2008)

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-641-2014 ◽

2014 ◽

Vol 14 (2) ◽

pp. 641-658 ◽

Cited By ~ 24

Author(s):

F. Chane Ming ◽

C. Ibrahim ◽

C. Barthe ◽

S. Jolivet ◽

P. Keckhut ◽

...

Keyword(s):

Tropical Cyclone ◽

Gravity Waves ◽

Radio Occultation ◽

Numerical Study ◽

Wide Spectrum ◽

Wave Number ◽

Southwest Indian Ocean ◽

Gps Radio Occultation ◽

Occultation Data ◽

Radio Occultation Data

Abstract. Gravity waves (GWs) with horizontal wavelengths of 32–2000 km are investigated during tropical cyclone (TC) Ivan (2008) in the southwest Indian Ocean in the upper troposphere (UT) and the lower stratosphere (LS) using observational data sets, radiosonde and GPS radio occultation data, ECMWF analyses and simulations of the French numerical model Meso-NH with vertical resolution < 150 m near the surface and 500 m in the UT/LS. Observations reveal dominant low-frequency GWs with short vertical wavelengths of 0.7–3 km, horizontal wavelengths of 80–400 km and periods of 4.6–13 h in the UT/LS. Continuous wavelet transform and image-processing tools highlight a wide spectrum of GWs with horizontal wavelengths of 40–1800 km, short vertical wavelengths of 0.6–3.3 km and periods of 20 min–2 days from modelling analyses. Both ECMWF and Meso-NH analyses are consistent with radiosonde and GPS radio occultation data, showing evidence of a dominant TC-related quasi-inertia GW propagating eastward east of TC Ivan with horizontal and vertical wavelengths of 400–800 km and 2–3 km respectively in the LS, more intense during TC intensification. In addition, the Meso-NH model produces a realistic, detailed description of TC dynamics, some high-frequency GWs near the TC eye, variability of the tropospheric and stratospheric background wind and TC rainband characteristics at different stages of TC Ivan. A wave number 1 vortex Rossby wave is suggested as a source of dominant inertia GW with horizontal wavelengths of 400–800 km, while shorter scale modes (100–200 km) located at northeast and southeast of the TC could be attributed to strong localized convection in spiral bands resulting from wave number 2 vortex Rossby waves. Meso-NH simulations also reveal GW-related clouds east of TC Ivan.

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Is DE2 the source of the ionospheric wave number 3 longitudinal structure?

Journal of Geophysical Research Atmospheres ◽

10.1029/2010ja015979 ◽

2010 ◽

Vol 115 (A11) ◽

pp. n/a-n/a ◽

Cited By ~ 12

Author(s):

H. Kil ◽

L. J. Paxton ◽

W. K. Lee ◽

Z. Ren ◽

S.-J. Oh ◽

...

Keyword(s):

Wave Number ◽

Longitudinal Structure ◽

Ionospheric Wave

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Electrodynamics of the formation of ionospheric wave number 4 longitudinal structure

Journal of Geophysical Research Atmospheres ◽

10.1029/2008ja013301 ◽

2008 ◽

Vol 113 (A9) ◽

pp. n/a-n/a ◽

Cited By ~ 81

Author(s):

H. Jin ◽

Y. Miyoshi ◽

H. Fujiwara ◽

H. Shinagawa

Keyword(s):

Wave Number ◽

Longitudinal Structure ◽

Ionospheric Wave

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Estimation of parameters of ionospheric wave disturbances on the basis of measurements of the Doppler shift of signal frequency of low-orbiting satellites

International Journal of Geomagnetism and Aeronomy ◽

10.1029/2006gi000147 ◽

2008 ◽

Vol 8 (1) ◽

Author(s):

T. V. Chmyga ◽

V. F. Pushin ◽

O. F. Tyrnov ◽

O. V. Alexanova

Keyword(s):

Doppler Shift ◽

Signal Frequency ◽

Estimation Of Parameters ◽

Wave Disturbances ◽

Ionospheric Wave

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Saturation mechanism and generated viscosity in gravito-turbulent accretion disks

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038023 ◽

2020 ◽

Vol 640 ◽

pp. A53

Author(s):

L. Löhnert ◽

S. Krätschmer ◽

A. G. Peeters

Keyword(s):

Growth Rate ◽

Numerical Simulations ◽

Accretion Disks ◽

Gravitational Instability ◽

Turbulent Viscosity ◽

Radial Distance ◽

Maximum Growth ◽

Wave Number ◽

Radiative Cooling ◽

Mixing Length

Here, we address the turbulent dynamics of the gravitational instability in accretion disks, retaining both radiative cooling and irradiation. Due to radiative cooling, the disk is unstable for all values of the Toomre parameter, and an accurate estimate of the maximum growth rate is derived analytically. A detailed study of the turbulent spectra shows a rapid decay with an azimuthal wave number stronger than ky−3, whereas the spectrum is more broad in the radial direction and shows a scaling in the range kx−3 to kx−2. The radial component of the radial velocity profile consists of a superposition of shocks of different heights, and is similar to that found in Burgers’ turbulence. Assuming saturation occurs through nonlinear wave steepening leading to shock formation, we developed a mixing-length model in which the typical length scale is related to the average radial distance between shocks. Furthermore, since the numerical simulations show that linear drive is necessary in order to sustain turbulence, we used the growth rate of the most unstable mode to estimate the typical timescale. The mixing-length model that was obtained agrees well with numerical simulations. The model gives an analytic expression for the turbulent viscosity as a function of the Toomre parameter and cooling time. It predicts that relevant values of α = 10−3 can be obtained in disks that have a Toomre parameter as high as Q ≈ 10.

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