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14 pages, 4877 KB

Open AccessEditor’s ChoiceArticle

C-Structures in Mesospheric Na and K Layers and Their Relations with Dynamical and Convective Instabilities

by Vania Fatima Andrioli, Jiyao Xu, Paulo Prado Batista, Laysa C. A. Resende, Alexandre A. Pimenta, Maria Paulete Martins, Siomel Savio, Cristiane Godoy Targon, Guotao Yang, Jing Jiao, Chi Wang and Zhengkuan Liu

Atmosphere 2022, 13(11), 1867; https://doi.org/10.3390/atmos13111867 - 9 Nov 2022

Cited by 4 | Viewed by 1996

Abstract

We analyzed the C-structures in the mesospheric metal layers. We used two datasets: one from a narrow band Sodium (Na) Density and Temperature LIDAR and the other from a high-resolution dual band Na and Potassium (K) LIDAR, both operated at São José dos Campos, Brazil (23° S, 46° W). We also investigated the Es layer occurrence and wind shear influences forming these structures. We found three C-type events over 82 analyzed nights in the first data set. They all showed lower temperatures inside C-structures compared to the borders. The squared Brunt-Väissälä frequency analyses showed positive values in the region of C-structures. In two out of three cases, dynamical instability was present (Ri < 0.25). We compared these results with the nine simultaneous C-type events identified in the 185 nights from the second data set. They showed height and time simultaneity correspondence as observed in the Na and K layers. Our results showed a low correlation between Es occurrence and C-structures. Additionally, strong wind shears in the altitude and time where C-structures appeared were always present. The advection of a metal cloud to the LIDAR station and a wind distortion seems to be the plausible mechanism that can explain all the observations. Full article

(This article belongs to the Special Issue Mesosphere and Lower Thermosphere)

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17 pages, 951 KB

Open AccessArticle

Effects of Linewidth Broadening Method on Recoil of Sodium Laser Guide Star

by Xiangyuan Liu, Xianmei Qian, Rui He, Dandan Liu, Chaolong Cui, Chuanyu Fan and Hao Yuan

Atmosphere 2021, 12(10), 1315; https://doi.org/10.3390/atmos12101315 - 8 Oct 2021

Cited by 3 | Viewed by 2912

Abstract

The linewidth broadening of the circular-polarized continuous wave laser mitigates the recoil effects of the sodium laser guide star very well. By choice of the optimal laser linewidth, the relations between the laser intensity and average spontaneous emission rates are obtained. The numerically simulated results show that the 1–100 MHz linewidth broadening effectively weakens recoil and enhances the average spontaneous emission rates. For laser powers from 10 W to 60 W, considering the intensity distribution with random at the mesospheric sodium layer, when the laser linewidth is broadened to be 1–100 MHz from 0 MHz, increments of the return photons go up to 110% from 50% and do not have an effect on the spot sizes of the sodium laser guide star. Several cases have proven that the linewidth broadening method is correct. Further calculations show that the linewidth broadening method similarly applies to the case of the multi-mode laser. Furthermore, the linewidth broadening of re-pumping should be taken into account. Full article

(This article belongs to the Special Issue Mesosphere and Lower Thermosphere: New Diagnostic Methods and Recent Observations II)

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12 pages, 4157 KB

Open AccessLetter

High Resolution 3-D Imaging of Mesospheric Sodium (Na) Layer Utilizing a Novel Multilayer ICCD Imager and a Na Lidar

by Xuewu Cheng, Guotao Yang, Tao Yuan, Yuan Xia, Yong Yang, Jiqin Wang, Kaijun Ji, Xin Lin, Lifang Du, Linmei Liu, Kaijie Ji and Faquan Li

Remote Sens. 2020, 12(22), 3678; https://doi.org/10.3390/rs12223678 - 10 Nov 2020

Cited by 2 | Viewed by 3166

Abstract

Equipped with a 1-meter Cassegrain telescope with 6.2 meter focal length and an electronically gated Intensified Charge-Coupled Device (ICCD), a multilayer Na imager is designed and developed at Wuhan in China. This novel instrument has successfully achieved the first preliminary 3-D image of the mesospheric Sodium (Na) layer when running alongside a Na lidar. The vertical Na layer profile is measured by the lidar, while the horizontal structure of the layer at different altitudes is measured by the ICCD imaging with a horizontal resolution of ~3.7 urad. In this experiment, controlled by the delay and width of the ICCD gating signal, the images of the layer are taken with three-second temporal resolution for every 5 km. The results show highly variable structures in both the vertical and horizontal directions within the Na layer. Horizontal images of the Na layer at different altitudes near both the permanent layer (80–100 km) and a sporadic Na layer at 117.5 km are obtained simultaneously for the first time. The Na number density profiles measured by the lidar and those derived from this imaging technique show excellent agreement, demonstrating the success of this observational technique and the first 3-D imaging of the mesospheric Na layer. Full article

(This article belongs to the Section Atmospheric Remote Sensing)

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10 pages, 443 KB

Open AccessArticle

Growth Rate of Gravity Wave Amplitudes Observed in Sodium Lidar Density Profiles and Nightglow Image Data

by Fabio Vargas, Guotao Yang, Paulo Batista and Delano Gobbi

Atmosphere 2019, 10(12), 750; https://doi.org/10.3390/atmos10120750 - 28 Nov 2019

Cited by 5 | Viewed by 3884

Abstract

Amplitude growth rates of quasi-monochromatic gravity waves were estimated and compared from multiple instrument measurements carried out in Brazil. Gravity wave parameters, such as the wave amplitude and growth rate in distinct altitudes, were derived from sodium lidar density and nightglow all-sky images. [...] Read more.

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W) from 1994 to 2004, while all-sky imagery of multiple airglow layers was conducted in Cachoeira Paulista (23

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S, 45

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W) from 1999–2000 and 2004–2005. We have found that most of the measured amplitude growth rates indicate dissipative behavior for gravity waves identified in both lidar profiles and airglow image datasets. Only a small fraction of the observed wave events (4% imager; 9% lidar) are nondissipative (freely propagating waves). Our findings also show that imager waves are strongly dissipated within the mesosphere and lower thermosphere region (MLT), decaying in amplitude in short distances (<12 km), while lidar waves tend to maintain a constant amplitude within that region. Part of the observed waves (16% imager; 36% lidar) showed unchanging amplitude with altitude (saturated waves). About 51.6% of the imager waves present strong attenuation (overdamped waves) in contrast with 9% of lidar waves. The general saturated or damped behavior is consistent with diffusive filtering processes imposing limits to amplitude growth rates of the observed gravity waves. Full article

(This article belongs to the Special Issue Atmospheric Airglow—Recent Advances in Observations, Experimentations, and Modeling)

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