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Proceedings with Extended Abstracts (single PDF file) - Radio ...

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4. SummaryThe high resolution (250s and 300m in time and height) Rayleigh lidar measurementsmade on two representative days during summer and <strong>with</strong>er is presented in this paper. Thelidar observations revealed significant gravity wave activity over the entire observed heightrange of 30-70 km. The wave activity is seen to be distinctly different from stratosphere tomesosphere. From the high-resolution temperature pro<strong>file</strong>s, revealing waves <strong>with</strong> verticalwavelength of the order of 5 – 10 km and downward phase descent of 0.2 – 0.4 ms -1 , it isinferred that long periods (~7 hrs) characterize the wave activity at stratospheric heights.These modes <strong>with</strong> low rate of vertical phase propagation, referred to as quasi-stationarymodes, are found to be similar to that observed over midlatitudes [e.g., Wilson et al., 1990]. Incontrast, the wave activity in the mesosphere is dominated by the relatively shorter periods,covering the observed range of ~16 – 270 min. The gravity wave activity is found to bemaximum during summer and minimum during winter, a behavior much different from that ofmid- and high latitudes where the maximum occurs in winter and minimum in summer.AcknowledgementThe National MST Radar facility (NMRF) is operated by the Department of Space<strong>with</strong> partial support from Council of Scientific & Industrial Research, Government of India.ReferencesAllen, S.J., and R.A.Vincent, Gravity wave activity in the lower atmosphere: Seasonal andlatitudinal variations, J. Geophys. Res., 100, 1327-1350, 1995.Beatty, T.J., C.A. Hostetler, and C.S.Gardner, Lidar observations of gravity waves and theirspectra near the Mesopause and Stratopause at Arecibo, J. Geophys. Res., 49, 472-497, 1992.Chanin, M.L., and A. Hauchecorne, Lidar observation of gravity and tidal waves in thestratosphere and mesosphere, J. Geophys. Res., 86, 9715-9721, 1981.Fritts, D.C., Gravity wave saturation in the middle atmosphere: A review of theory andobservations, Rev. Geophys. Space Phys., 22, 275-308, 1984.Fritts, D.C., and P.K. Rastogi, Convective and dynamical instabilities due to gravity wavemotions in the lower and middle atmosphere: Theory and observations, <strong>Radio</strong> Sci., 20, 1247-1277, 1985.Fritts, D.C., and T.E. vanZandt, Spectral estimates of gravity wave energy and momentumfluxes, 1. Energy dissipation, acceleration, and constraints, J. Atmos. Sci., 50, 3685-3694, 1993.Gardner, C.S., M.S. Miller, and C.H.Liu, Rayleigh lidar observations of gravity wave activityin the upper stratosphere at Urbana, Illonois, J. Atmos. Sci., 46, 1838-1854, 1989.Gavrilov, N.M., S. Fukao, T. Nakamura., Gravity wave intensity and momentum fluxes in themesosphere over Shigaraki, Japan (35°N ; 136°E) during 1987-1997, Ann. Geophys., 18, 834-843, 2000.Hauchecorne, A., and M.L. Chanin, Density and temperature pro<strong>file</strong>s obtained by lidarbetween 35 and 70 km, Geophys. Res. Lett., 7, 565-568, 1980.Wilson, R., A. Hauchecorne and M.L. Chanin, Gravity waves in the middle atmosphereobserved by Rayleigh lidar, Part 2: Climatology, J. Geophys. Res., 96, 5169-5183, 1990.244

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