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Ann. Geophys., 25, 1759-1766, 2007
www.ann-geophys.net/25/1759/2007/
© European Geosciences Union 2007
Lidar observations of sporadic Na layers over Gadanki (13.5° N, 79.2° E)
P. Vishnu Prasanth, S. Sridharan, Y. Bhavani Kumar, and D. Narayana Rao
National Atmospheric Research Laboratory, Gadanki-517 112, Pakala Mandal, Chitoor District, Andhra Pradesh, India
Abstract. We studied the characteristics of sporadic sodium layers (SSLs) observed with
the sodium (Na) resonance scattering lidar at Gadanki (13.5° N, 79.2° E).
The SSLs were observed on a total of 63 occasions during 464 h of
Na lidar observations from January 2005 to February 2006. The observations
showed that one SSL event occurred, on average, every 7 h. The most
prominent sporadic layer, which formed on 12 February 2005, exhibited a peak
density of 60 722 Na atoms/cm³ around 92 km and it was nearly twice the
peak density reported from elsewhere using ground-based observations. In
general, the SSLs exhibited the following characteristics: (1) they
developed at heights between 88 and 98 km with an average height around
94 km;
(2) maximum density occurred during the early morning hours between 02:00 and
05:00 IST; (3) the ratio of the maximum peak Na density to the average
density was normally around 3 to 5 and it exceeded even 10 in some cases;
(4) the events lasted from a few minutes to several hours. The formation
period of the SSLs was longer compared to the decay period of the SSLs. Most
of the SSL events showed downward motions.
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