Lidar Observations of Sporadic Fe and Na Layers in the Mesopause Region over Equator

Shibata, Yasukuni; Nagasawa, Chikao; Abo, Makoto; Maruyama, Takashi; Saito, Susumu; Nakamura, Takuji

doi:10.2151/jmsj.84a.317

Cited by 12 publications

(13 citation statements)

References 23 publications

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“…7. The apparent phase velocity is about 1.0 km h −1 or 30 cm s −1 , which is consistent with the reported values of the semidiurnal tide in Na layer (Simonich et al, 1979;Kwon et al, 1987).…”

Section: Wave Parameterssupporting

confidence: 91%

“…• S) (Shibata et al, 2006), however, there no measurements at other lower latitudes. Another important feature of the sodium layer is the event of sporadic sodium, occurrence of sharp sodium densities in short time, whose formation mechanism is still not understood.…”

Section: Introductionmentioning

confidence: 92%

“…It shows a variation of more than 400 percent. Simonich et al (1979) found an average nocturnal variation by a factor of 2 in the sodium column abundance at 23…”

Section: Na Layer Propertiesmentioning

confidence: 97%

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The first lidar observations of the nighttime sodium layer at low latitudes Gadanki (13.5°N, 79.2°E), India

et al. 2007

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We report on the first lidar observations of the nighttime mesospheric sodium layer from Gadanki (13.5 • N, 79.2• E) site in India. The lidar measurements of upper atmospheric sodium made on 6 nights between the 10 and 16 January 2005 are presented in this paper. The Gadanki lidar uses a Nd:YAG pumped dye laser, tuned to the sodium D2 line (589.0 nm), as a transmitter. Using the system, sodium number density profiles have been obtained with a vertical resolution of 300 m, a time sampling of 120 s. During the initial six nights of observation, the peak sodium concentration is found at a height of 95 km, and the top side scale height is usually about 2 km. On three occasions, a secondary peak was observed at heights between 87 and 92 km. Measurements at Gadanki site indicate that the mean sodium abundances appear to decrease after sunset and increase before sunrise. The average nocturnal columnar abundances were in the range 2-8.9×109 cm −2 . The nightly mean centroid heights range between 92.9 and 95.2 km and the rms widths vary between 4.3 and 4.9 km. On some nights, wave like structures in the sodium layer were observed with wavelength of about 3 km and downward phase velocities of about 1 km/hr. Four sporadic layers were observed during the initial 54 h of observation. The formation and decay of an intense sporadic sodium layer was observed on the night of 11 January 2005. The layer was found to develop between 93 and 90 km altitude and appear between 0230 and 0430 LT.

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Section: Wave Parameterssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 92%

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The first lidar observations of the nighttime sodium layer at low latitudes Gadanki (13.5°N, 79.2°E), India

et al. 2007

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“…In addition, the normal Na layer always showed a few kilometers more extension on its top side than the normal Fe layer. These features can be clearly seen also from a comparison of simultaneously observed Fe and Na layers at high, mid and low latitudes respectively [ Kane and Gardner , 1993; Lynch et al , 2005; Shibata et al , 2006]. Thus these features may be universal, in which case they may provide a connection between the two different metallic species and reflect the physics and/or chemistry in their formation.…”

Section: Introductionmentioning

confidence: 90%

Some ubiquitous features of the mesospheric Fe and Na layer borders from simultaneous and common‐volume Fe and Na lidar observations

Zhang

Yue

et al. 2008

J. Geophys. Res.

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[1] High-accuracy atom density profiles, obtained by the simultaneous and commonvolume Fe and Na lidar measurements at Wuhan, China (30.5°N, 114.4°E), reveal some ubiquitous features of the Fe and Na layers on their borders. The Fe and Na lower boundaries show consistently a delicate stratification in which the lower boundary of the Fe layer is in general slightly higher than or coincident with that of the Na layer, with an overall mean altitude difference being about 0.2 km. Despite the existence of considerable vertical displacements, the two lower boundaries vary always following almost the same track. The overall correlation coefficient between them is as high as 0.96. This ubiquitous delicate stratification of the measured lower boundaries (nearly coincident density cutoff ) suggests strongly that the undersides of Fe and Na layers are controlled by the same or very similar processes. The upper boundary of the Na layer is always several kilometers higher than that of the Fe layer. A relatively weak positive correlation is also persistently observed between the two upper boundaries. Weak sporadic layering events frequently occur on the upper extent of the metal layers. They may impair the correct determination of the upper boundaries of the normal metal layers and consequently weaken the correlation. Both the Fe and Na layers often show an evidently steeper density gradient on the underside than on the upper extent, and the borders of the Fe layer are clearly steeper than those of the Na layer. The explanation to these ubiquitous features needs further experimental and modeling efforts.

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“…A high correlation between the occurrences of Na s layers and E s layers has led to suggesting the neutralization of the Na ion reservoir in the E s layers as a source of the neutral Na atoms (von Zahn and Hansen, 1988;Beatty et al, 1989;Kane and Gardner, 1993;Cox and Plane, 1998;Clemesha et al, 1999;Shibata et al, 2006;Williams et al, 2006Williams et al, , 2007Delgado et al, 2012;Yuan et al, 2013;Dou et al, 2013). In addition, according to several chemical theoretical studies, the Na ion is converted into a Na atom at a height around or above 100 km (Cox and Plane, 1998;Hansen and von Zahn, 1990;Collins et al, 2002).…”

Section: Z Ma Et Al: First Report Of Sporadic Na Layers At Qingdaomentioning

confidence: 99%

First report of sporadic Na layers at Qingdao (36° N, 120° E), China

Wang

Chen³

et al. 2014

Ann. Geophys.

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Abstract. This paper reports, for the first time, observational results of mesopause sporadic Na (Na s ) layers by a ground-based lidar at Qingdao (36 • N, 120 • E), China. Based on ∼ 430 h of observational data on 95 nights from December 2007 to June 2012, we have selected a total of 53 Na s layer events. It is found that characteristics of Na s layers over Qingdao have general similarity with those over nearby sites, Wuhan (30 • N, 114 • E) and Hefei (32 • N, 117 • E), but not those over the site Hachioji (35 • N, 139 • E) at nearly the same latitude as Qingdao. At the same time, parameters of sporadic E (E s ) layers were recorded by an ionosonde. The fact that E s layer occurrence probabilities of 19, 22, and 18 % in time intervals before, during, and after the Na s layers are very close to the average occurrence ratio of the nocturnal E s layer (21 %), may reveal a general independence between Na s and E s layers over Qingdao. Only those strong Na s layers above the peak altitude of the main Na layer might have a significant correlation with E s layers. In addition, a total of 11 high-altitude (above 105 km) Na s layer events have been surveyed specially. It is found that these high-altitude Na s layers were usually weak. And they possessed long-duration (> 147 min) and broad-layer width (4.0 km) compared with Na s layers below 105 km (> 96 min and 2.4 km). These characteristics are in accord with observational results at Wuhan. It is suggested that there is little correlation between this kind of Na s layers and E s layers. Finally, the summer topside enhancement phenomenon of Na atoms observed at Qingdao is in accord with several earlier observational results at different sites (18, 30, and 54 • N) in the Northern Hemisphere.

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Lidar Observations of Sporadic Fe and Na Layers in the Mesopause Region over Equator

Cited by 12 publications

References 23 publications

The first lidar observations of the nighttime sodium layer at low latitudes Gadanki (13.5°N, 79.2°E), India

The first lidar observations of the nighttime sodium layer at low latitudes Gadanki (13.5°N, 79.2°E), India

Some ubiquitous features of the mesospheric Fe and Na layer borders from simultaneous and common‐volume Fe and Na lidar observations

First report of sporadic Na layers at Qingdao (36° N, 120° E), China

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