A statistical study of sporadic sodium layer observed by Sodium lidar at Hefei (31.8° N, 117.3° E)

Dou, Xiankang; Xue, Xianghui; Chen, T.-D.; Wan, Weixing; Cheng, Xuewu; Li, Ting; Chen, C.; Qiu, Shican; Chen, Z.-Y.

doi:10.5194/angeo-27-2247-2009

Cited by 36 publications

(47 citation statements)

References 48 publications

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“…At low latitudes of the southern hemisphere (23°S), the Nas occurrence was relatively low [ Batista et al ., ]. At middle‐latitude East Asia, i.e., ~30°N, the Nas occurrence rate was approximately 10% [ Dou et al ., ; Gong et al ., ; Nagasawa and Abo , ; Yi et al ., ]. Thus, the Nas occurrence at Beijing is lower than other sites at middle‐latitude East Asia; this difference may have latitude dependence.…”

Section: Discussionmentioning

confidence: 99%

First report of sporadic K layers and comparison with sporadic Na layers at Beijing, China (40.6°N, 116.2°E)

et al. 2015

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A double-laser beam lidar was successfully developed to simultaneously measure K and Na layers at Beijing (40.6°N, 116.2°E) in 2010. Statistical analysis of the parameters of sporadic K (K s ) and sporadic Na (Nas) layers was performed over 2 years of lidar data, and different characteristics of them were found. The average K s occurrence (2.9%) was lower than that of Nas (5.9%); the Nas occurrence had a maximum (19.3%) in May-June months and a minimum (1.6%) in January-February months, while the K s occurrence had a maximum (4.9%) in January-February months and a minimum (1.0%) in September-October months; most K s peaks tended to occur around 93 km, which was~2 km lower than that of Nas (~95 km); the K s peak density was often at least 1 order of magnitude lower than that of Nas; notably, two K s with high peak densities (>1000 cm À3 ) were observed, which were much higher than K density (15-300 cm À3 ) reported before. The ascending time of K s was often longer than its descending time, but an opposite trend occurred for Nas. During the 152 cases of joint observation for the K and Na layers, 21% (32/152) were cases in which K s and Nas events simultaneously occurred, while 79% (120/152) were cases in which only one layer (K or Na) exhibited a strong K s or Nas.

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Section: Discussionmentioning

confidence: 99%

First report of sporadic K layers and comparison with sporadic Na layers at Beijing, China (40.6°N, 116.2°E)

et al. 2015

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“…One of these features is the occurrence of sporadic (or sudden) metal atom layers, which was first reported by Clemesha and Kirchhoff [] using ground‐based sodium lidar and is defined as an abrupt increase in the metal density over the level of the background layers. Sporadic metal layers, such as sporadic sodium layers (SSLs), appear widely at low and high latitudes as well as at some middle latitudes [ Nagasawa and Abo , ; Dou and Xue , ]. The horizontal dimensions of the sporadic metal layers usually extend to a large area, varying from hundreds to thousands of kilometers [ Kane and Hostetler , ; Fan and Plane , ].…”

Section: Introductionmentioning

confidence: 99%

Lower thermospheric‐enhanced sodium layers observed at low latitude and possible formation: Case studies

et al. 2013

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[1] We report two lower thermospheric-enhanced sodium layer (TeSL) cases observed at a low-latitude station, Lijiang, China (26.7°N, 100.0°E), on 10 March and 10 April 2012, respectively. The TeSLs in the two cases were located at altitudes near 122 and 112 km, respectively. In addition, strong sporadic sodium layers (SSLs) near 100 km accompanied the TeSL observed on 10 March 2012. Both the TeSLs and SSLs exhibited tidal-induced downward motion. The adjacent ground-based and space-borne ionospheric radio observations showed strong E s layers before the appearance of the TeSLs, suggesting an "E s -TeSLs (SSLs)" chain formed through the tidal wind shear mechanism. Assuming that the vertical tidal wavelengths remain unchanged, it is found that in different regions caused by the tidal wind shear, different TeSLs evolution processes are expected: (1) in a tidal-convergence region, a TeSL/SSL with a downward propagation phase is enhanced due to a rapid decrease in the Na + lifetime at the lower altitude; (2) in an ion convergencedivergence interface region, a TeSL/SSL will still follow the tidal downward phase progression, but sodium density does not exhibit evident enhancement; and (3) when a TeSL/SSL enters into a tidal wind-divergence zone, the layer density tends to decrease.

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“…Several observations of Na S have been reported (e.g. Kane et al 1991;Fan et al 2007;Dou et al 2009) wherein they deal with the correlation of Na S events with E S events. In this context, it is also to be noted that high altitude sporadic metal layers (or high altitude metal layers) have been reported from several observational sites (e.g.…”

Section: Introductionmentioning

confidence: 99%

A case study on occurrence of an unusual structure in the sodium layer over Gadanki, India

et al. 2015

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The height-time-concentration map of neutral sodium (Na) atoms measured by a Na lidar during the night of 18 to 19 March 2007 over Gadanki, India (13.5°N, 79.2°E) reveals an unusual structure in the Na layer for around 30 min in the altitude range of 92 to 98 km which is similar to the usual 'C' type structures observed at other locations. In order to understand the physical mechanism behind the generation of this unusual event, an investigation is carried out combining the data from multiple instruments that include the meteor wind radar over Thiruvananthapuram, India (8.5°N, 77°E) and the SABER instrument onboard the TIMED satellite. The temperature and wind profiles from the data set provided by these instruments allow us to infer the Richardson number which is found to be noticeably less than the canonical threshold of 0.25 above 92 km over Thiruvananthapuram suggesting the plausible generation of Kelvin-Helmholtz (KH) billows over southwestern part of the Indian subcontinent. Based on the average wind speed and direction over Thiruvananthapuram, it is proposed that the KH-billow structure was modified due to the background wind and was advected with it in nearly 'frozen-in' condition (without significant decay) in the northeastward direction reaching the Na lidar location (Gadanki). This case study, therefore, presents a scenario wherein the initially deformed KH-billow structure survived for a few hours (instead of a few minutes or tens of minutes as reported in earlier works) in an apparently 'frozen-in' condition under favorable background conditions. In this communication, we suggest a hypothesis where this deformed KH-billow structure plays crucial role in creating the abovementioned unusual structure observed in the Na layer over Gadanki.

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A statistical study of sporadic sodium layer observed by Sodium lidar at Hefei (31.8° N, 117.3° E)

Cited by 36 publications

References 48 publications

First report of sporadic K layers and comparison with sporadic Na layers at Beijing, China (40.6°N, 116.2°E)

First report of sporadic K layers and comparison with sporadic Na layers at Beijing, China (40.6°N, 116.2°E)

Lower thermospheric‐enhanced sodium layers observed at low latitude and possible formation: Case studies

A case study on occurrence of an unusual structure in the sodium layer over Gadanki, India

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