TY - JOUR
T1 - A case study on occurrence of an unusual structure in the sodium layer over Gadanki, India
AU - Sarkhel, Sumanta
AU - Mathews, John D.
AU - Raizada, Shikha
AU - Sekar, Ramanathan
AU - Chakrabarty, Dibyendu
AU - Guharay, Amitava
AU - Jee, Geonhwa
AU - Kim, Jeong Han
AU - Kerr, Robert B.
AU - Ramkumar, Geetha
AU - Sridharan, Sundararajan
AU - Wu, Qian
AU - Mlynczak, Martin G.
AU - Russell, James M.
N1 - Funding Information:
J. D. Mathews’ and part of S. Sarkhel’s component of this effort was supported under the National Science Foundation (NSF) grant ATM 07-21613 and AGS 1241407 to The Pennsylvania State University, USA. The Arecibo Observatory is operated by SRI International under a cooperative agreement with the NSF (AST-1100968), and in alliance with Ana G. Méndez-Universidad Metropolitana, and the Universities Space Research Association. A. Guharay acknowledges support of the Fundação de Amparo à Pesquisa do Estado de São Paulo, Brazil to this present research work. G. Jee, J. Kim, and part of S. Sarkhel’s effort is supported by grant PE15010 in the Korea Polar Research Institute, South Korea. NCAR is supported by the NSF. The SKiYMET radar installed at the Space Physics Laboratory was sanctioned under the 10th 5-year plan of the Department of Space, Government of India. The authors thank the director and the supporting staff members of the National Atmospheric Research Laboratory, Gadanki, India for their cooperation in making the observational campaign successful. S. Sarkhel thanks V. Lakshmi Narayanan and S. Gurubaran for useful discussion. This work is also partially supported by the Department of Space, Government of India.
Publisher Copyright:
© 2015 Sarkhel et al.; licensee Springer.
PY - 2015/2
Y1 - 2015/2
N2 - 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.
AB - 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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U2 - 10.1186/s40623-015-0183-5
DO - 10.1186/s40623-015-0183-5
M3 - Article
AN - SCOPUS:84923169995
VL - 67
JO - Earth, Planets and Space
JF - Earth, Planets and Space
SN - 1343-8832
IS - 1
M1 - 19
ER -