Determinação dos parâmetros de ondas de gravidade através da análise espectral de imagens de aeroluminescência

Wrasse, C. M.; Takahashi, H.; Medeiros, A. F.; Lima, Lourivaldo Mota; Taylor, Michael J.; Gobbi, D.; Fechine, J.

doi:10.1590/s0102-261x2007000300003

Cited by 20 publications

(30 citation statements)

References 8 publications

(9 reference statements)

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“…The main MSTID parameters can be determined, such as the phase velocity, horizontal wavelength, period, and propagation direction. The details of each step can be found in Medeiros et al (2003), Wrasse et al (2007), and Paulino et al (2016).…”

Section: Instrumentation and Methodologymentioning

confidence: 99%

Investigation of Nighttime MSTIDS Observed by Optical Thermosphere Imagers at Low Latitudes: Morphology, Propagation Direction, and Wind Filtering

et al. 2018

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Different types of medium‐scale traveling ionospheric disturbances (MSTIDs) have been observed at Cachoeira Paulista (22.4°S; 45.0°W), Brazil, from June 2013 to December 2015, using airglow OI 630.0‐nm images. During the period, 58 MSTIDs were identified and classified as follows: dark band MSTIDs (around 10 events) and periodic MSTIDs (48 events). Dark band MSTIDs present phase velocity between 50 and 200 m/s and propagation direction to northwestward. On the other hand, periodic MSTIDs have phase velocity of 50 to 200 m/s, horizontal wavelengths from 80 to 160 km, periods ranging between 5 and 45 min, and propagation directions are mainly north‐northeastward. The wave parameters indicate that periodic MSTIDs have different characteristics when compared to dark band MSTIDs, suggesting that periodic MSTIDs are not generated through the well‐known Perkins and E‐F coupling instability. In addition to it, the present study indicates that the spectral characteristics found in Brazil are different from other regions such as Japan and Indonesia. Therefore, we intend to do the statistics of the wave parameters (wavelength, phase velocity, period, propagation direction, and time occurrence) and investigate the generation mechanisms of periodic MSTIDs at low to middle latitude for the first time. Furthermore, the anisotropy observed in periodic MSTID propagation direction can be explained by different mechanisms.

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Section: Instrumentation and Methodologymentioning

confidence: 99%

Investigation of Nighttime MSTIDS Observed by Optical Thermosphere Imagers at Low Latitudes: Morphology, Propagation Direction, and Wind Filtering

et al. 2018

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“…In order to obtain the parameters of the observed fronts, a two-dimensional FFT (fast Fourier transform) was used, following the methodology described by Wrasse et al (2007). The methodology consists of selecting a rectangular area in a sequence of 4-5 images; this area must contain the oscillation on all selected images where the front can be seen clearly, without the Milky Way contamination, and this area must contain the wave structure.…”

Section: Instrumentation and Methodologymentioning

confidence: 99%

Mesospheric front observations by the OH airglow imager carried out at Ferraz Station on King George Island, Antarctic Peninsula, in 2011

et al. 2018

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Abstract. The main goals of this work are to characterize and investigate the potential wave sources of four mesospheric fronts identified in the hydroxyl near-infrared (OH-NIR) airglow images, obtained with an all-sky airglow imager installed at Comandante Ferraz Antarctic Station (EACF, as per its Portuguese acronym) located on King George Island in the Antarctic Peninsula. We identified and analyzed four mesospheric fronts in 2011 over King George Island. In addition, we investigate the atmospheric background environment between 80 and 100 km altitude and discuss the ducts and propagation conditions for these waves. For that, we used wind data obtained from a meteor radar operated at EACF and temperature data obtained from the TIMED/SABER satellite. The vertical wavenumber squared, m 2 , was calculated for each of the four waves. Even though no clearly defined duct (indicated by positive values of m 2 sandwiched between layers above and below with m 2 < 0) was found in any of the events, favorable propagation conditions for horizontal propagation of the fronts were found in three cases. In the fourth case, the wave front did not find any duct support and it appeared to dissipate near the zenith, transferring energy and momentum to the medium and, consequently, accelerating the wind in the wave propagation direction (near to south) above the OH peak (88-92 km). The likely wave sources for these four cases were investigated by using meteorological satellite images and in two cases we could find that strong instabilities were potential sources, i.e., a cyclonic activity and a large convective cloud cell. In the other two cases it was not possible to associate troposphere sources as potential candidates for the generation of such wave fronts observed in the mesosphere and secondary wave sources were attributed to these cases.

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“…The images were corrected for the warped field of view and a second order high-pass Butterworth filter was applied. The gravity wave parameters were obtained by using the standard 2-D FFT analysis (Garcia et al, 1997;Medeiros et al, 2003;Wrasse et al, 2007). The amplitude and phase of the cross spectrum was obtained by a sequence of at least 4 images, which allows us to calculate the gravity wave horizontal wavelength (λ h ), propagation direction (φ), observed phase speed (c obs ) and period (τ obs ).…”

Section: Observations and Methodologymentioning

confidence: 99%

Observation of mesospheric gravity waves at Comandante Ferraz Antarctica Station (62° S)

et al. 2009

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Abstract. An airglow all-sky imager was operated at Comandante Ferraz Antarctica Station (62.1 • S, 58.4 • W), between April and October of 2007. Mesospheric gravity waves were observed using the OH airglow layer during 43 nights with good weather conditions. The waves presented horizontal wavelengths between 10 and 60 km and observed periods mainly distributed between 5 and 20 min. The observed phase speeds range between 5 m/s and 115 m/s; the majority of the wave velocities were between 10 and 60 m/s. The waves showed a preferential propagation direction towards the southwest in winter (May to July), while during spring (August to October) there was an anisotropy with a preferential propagation direction towards the northwest. Unusual mesospheric fronts were also observed. The most probable wave source could be associated to orographic forcing, cold fronts or strong cyclonic activity in the Antarctica Peninsula.

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Determinação dos parâmetros de ondas de gravidade através da análise espectral de imagens de aeroluminescência

Cited by 20 publications

References 8 publications

Investigation of Nighttime MSTIDS Observed by Optical Thermosphere Imagers at Low Latitudes: Morphology, Propagation Direction, and Wind Filtering

Investigation of Nighttime MSTIDS Observed by Optical Thermosphere Imagers at Low Latitudes: Morphology, Propagation Direction, and Wind Filtering

Mesospheric front observations by the OH airglow imager carried out at Ferraz Station on King George Island, Antarctic Peninsula, in 2011

Observation of mesospheric gravity waves at Comandante Ferraz Antarctica Station (62° S)

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