Correspondence to: P. Vishnu Prasanth

Abstract. In this paper, we present seasonal and nocturnal variations of mesospheric sodium (Na) layer parameters ob-served over Gadanki (13.5 ◦ N, 79.2 ◦ E), based on 166 nights during the period from January 2005 to December 2006, for the first time. The total Na content decreases during the evening and reaches a minimum value around midnight and maximum in the early morning. The year-to-year variations illustrate that Na layers reach the peak value close to 93.5 km for the year 2005 and ∼93 km for the year 2006 and falls to near zero value around 110 km. Though, seasonal varia-tion of sodium density illustrate maximum values in Septem-ber, December and March, we require a larger data base for September months to conclude the statement. The col-umn abundance shows maximum during autumn equinox and minimum during winter. The obtained seasonal and noctur-nal variation of sodium layer parameters are compared with mid-latitude observations and further possible mechanisms are discussed. Keywords. Atmospheric composition and structure (Mid-dle atmosphere – composition and chemistry) – Meteorol-ogy and atmospheric dynamics (Middle atmosphere dynam-ics; Waves and tides