High-resolution observations of mesospheric layers with the Jicamarca VHF radar

Lehmacher, G. A.; Guo, Lixin; Kudeki, Erhan; Reyes, Pablo; Akgiray, Ahmed; Chau, Jorge L.

doi:10.1016/j.asr.2007.05.059

Cited by 37 publications

(43 citation statements)

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“…We show spectral width only for echoes above −10 dB SNR and for widths greater than 1 m/s, since values for very weak echoes are less reliable, and beam broadening effects contribute 0.1 to 0.7 m/s to the spectral width (Guo et al, 2007). Wide spectra with positive power-width correlation are interpreted as caused by turbulent fluctuations (e.g., Hocking, 1985;Sheth et al, 2006) and have been used to derive turbulent energy dissipation rates for Jicamarca (Guo et al, 2007). Median turbulent energy dissipation rates estimated from spectral widths are around 10 mW/kg, but can vary between 1 and 100 mW/kg, with values generally increasing with altitude throughout the mesosphere.…”

Section: Resultsmentioning

confidence: 99%

“…Then we calculate volume reflectivities σ for three levels of turbulent activity, ε=0.001, 0.01, and 0.1 W/kg. These values are generally observed in the mesosphere by radar and rockets (e.g., Fukao et al, 1994;Lübken, 1997), and also at Jicamarca (Guo et al, 2007). While the Richardson number or rather the horizontal wind shear Ri/ω 2 B can be determined from Jicamarca winds, we are here interested in an average value and use Ri=0.81 as in other papers.…”

Section: Estimates From Turbulence Theorymentioning

confidence: 99%

“…Spectral fitting allows us to estimate very small signals with spectral widths down to about 1 m/s. (Sheth et al, 2006;Guo et al, 2007). Figure 1 shows a fairly broad spectrum fitted by a generalized Gaussian to the logarithm of the power spectrum.…”

Section: Calibration Of Radar Cross Sectionsmentioning

confidence: 99%

“…For a constant level of turbulence, RCS decreases with altitude, and is mainly the effect of the increasing inner scale. The thick line uses epsilon values increasing from 0.010 to 0.100 mW/kg according to Jicamarca observations (Guo et al, 2007), which will somewhat equalize the RCS spread. While there is a large variability in individual layers, the main point is that the largest RCS appear around 70 km, which is consistent with the main level of echo layers observed at Jicamarca, which is between 70 and 75 km.…”

Section: Estimates From Turbulence Theorymentioning

confidence: 99%

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Radar cross sections for mesospheric echoes at Jicamarca

et al. 2009

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Abstract.Radar cross sections (RCS) of mesospheric layers at 50 MHz observed at Jicamarca, Peru, range from 10 −18 to 10 −16 m −1 , three orders of magnitudes smaller than cross sections reported for polar mesospheric winter echoes during solar proton events and six orders of magnitude smaller than polar mesospheric summer echoes. Large RCS are found in thick layers around 70 km that also show wide radar spectra, which is interpreted as turbulent broadening. For typical atmospheric and ionospheric conditions, volume scattering RCS for stationary, homogeneous, isotropic turbulence at 3 m are also in the range 10 −18 to 10 −16 m −1 , in reasonable agreement with measurements. Moreover, theory predicts maximum cross sections around 70 km, also in agreement with observations. Theoretical values are still a matter of order-of-magnitude estimation, since the Bragg scale of 3 m is near or inside the viscous subrange, where the form of the turbulence spectrum is not well known. In addition, steep electron density gradients can increase cross-sections significantly. For thin layers with large RCS and narrow spectra, isotropic turbulence theory fails and scattering or reflection from anisotropic irregularities may gain relevance.

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Section: Resultsmentioning

confidence: 99%

Section: Estimates From Turbulence Theorymentioning

confidence: 99%

Section: Calibration Of Radar Cross Sectionsmentioning

confidence: 99%

Section: Estimates From Turbulence Theorymentioning

confidence: 99%

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Radar cross sections for mesospheric echoes at Jicamarca

et al. 2009

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“…For instance, Manson et al (1981) report energy values of 1 Â 10 À3 J/m 3 at the altitude of 90 km for gravity waves having periods <1 h at 52°N latitude. At lower latitudes, Lehmacher et al (2007) using the Jicamarca VHF radar measured an energy dissipation rate e $ 0.12 W/kg at mesospheric level. …”

Section: Oscillatory Kinetic Energy Of the Wave Systemmentioning

confidence: 99%

3D Imaging of the OH mesospheric emissive layer

Kouahla

Moreels

Faivre

et al. 2010

Advances in Space Research

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Modeling the implications of Kelvin‐Helmholtz instability dynamics for airglow observations

et al. 2014

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A companion paper describes high-resolution, ground-based imaging of apparent Kelvin-Helmholtz instabilities (KHI) observed in OH airglow at~87 km over the Andes Lidar Observatory at 30°S. Here we employ direct numerical simulations (DNSs) and large eddy simulations (LESs) of KHI at Richardson numbers from Ri = 0.05 to 0.20 and relatively high Reynolds numbers of Re~2500 to 10,000 to illustrate the dependence of primary and secondary KHI on these quantities for the purpose of quantifying KHI dynamics observed by ground-based airglow imagers. Our DNS and LES reveal significant variations of both primary and secondary KHI scales and amplitudes with varying Ri and Re. Lower Ri and higher Re yield stronger and deeper initial 2-D KH billows. Low Re for a given Ri either yield larger-scale 3-D secondary instabilities or suppress them altogether. Secondary instability scales decrease as Re increases for a given Ri. Corresponding variations in implied KHI airglow signatures include (1) stronger airglow intensity variations for larger KHI wavelengths and depths (higher Ri), (2) stronger 2-D and 3-D responses for the initial KHI shear layer displaced somewhat from the airglow layer, and (3) stronger 3-D responses for the lower Ri and intermediate Re yielding the larger secondary instability scales.

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High-resolution observations of mesospheric layers with the Jicamarca VHF radar

Cited by 37 publications

References 28 publications

Radar cross sections for mesospheric echoes at Jicamarca

Radar cross sections for mesospheric echoes at Jicamarca

3D Imaging of the OH mesospheric emissive layer

Modeling the implications of Kelvin‐Helmholtz instability dynamics for airglow observations

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