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Ann. Geophys., 24, 823-834, 2006
www.ann-geophys.net/24/823/2006/
© European Geosciences Union 2006
Lidar observations of middle atmospheric gravity wave activity over a low-latitude site (Gadanki, 13.5° N, 79.2° E)
V. Sivakumar1,2, P. B. Rao3, and H. Bencherif1
1Laboratoire de l’Atmosphère et des Cyclones, CNRS–UMR 8105, Université de La Réunion, 97715 Saint-Denis Messag. Cedex 9, La Reunion, France
2Initially at National Atmospheric Research Laboratory, Gadanki-517 502, India
3National Remote Sensing Agency, Bala Nagar, Hyderabad-500 037, India
Abstract. The low-latitude middle atmospheric gravity wave characteristics are
presented using 310 nights of Rayleigh lidar observations made at Gadanki
(13.5° N, 79.2° E) over the period from March 1998 to December 2002.
The gravity wave characteristics are presented in terms of vertical wave
number and frequency spectra, along with the estimated potential energy for
the four seasons, namely, spring, summer, autumn and winter. The computed
wave number spectra for both the stratosphere and the mesosphere are found to
differ significantly from a saturated model predicted spectrum. The spectra
were found to be shallower at lower wave numbers and steeper at higher wave numbers with
transition at ~8.85×10-4 cy/m. The computed frequency spectra
seem to follow the model plot with a power law index of -5/3 above a
frequency of ~2×10-4 Hz. The estimated potential energy per
unit mass increases gradually up to ~60 km and then rather rapidly
above this height to reach values of the order of 200J/kg at ~70 km.
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