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Ann. Geophys., 23, 3237-3260, 2005
www.ann-geophys.net/23/3237/2005/
© European Geosciences Union 2005
Studies on atmospheric gravity wave activity in the troposphere and lower stratosphere over a tropical station at Gadanki
I. V. Subba Reddy1, D. Narayana Rao2, A. Narendra Babu1, M. Venkat Ratnam3, P. Kishore4, and S. Vijaya Bhaskara Rao1
1Department of Physics, Sri Venkateswara University, Tirupati - 517 502, India
2National MST Radar Facility, Department. of Space, Gadanki - 517 112, India
3Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611 0011, Japan
4National Institute of Information and Communications Technology, Tokyo 184-8795, Japan
Abstract. MST radars are powerful tools to study the mesosphere, stratosphere and
troposphere and have made considerable contributions to the studies of the
dynamics of the upper, middle and lower atmosphere. Atmospheric gravity waves
play a significant role in controlling middle and upper atmospheric
dynamics. To date, frontal systems, convection, wind shear and topography
have been thought to be the sources of gravity waves in the troposphere. All
these studies pointed out that it is very essential to understand
the generation, propagation and climatology of gravity waves. In this regard,
several campaigns using Indian MST Radar observations have been carried out
to explore the gravity wave activity over Gadanki in the troposphere and the
lower stratosphere. The signatures of the gravity waves in the wind fields
have been studied in four seasons viz., summer, monsoon, post-monsoon and
winter. The large wind fluctuations were more prominent above 10 km during
the summer and monsoon seasons. The wave periods are ranging from 10 min-175 min.
The power spectral densities of gravity waves are found to be maximum
in the stratospheric region. The vertical wavelength and the propagation
direction of gravity waves were determined using hodograph analysis. The
results show both down ward and upward propagating waves with a maximum
vertical wave length of 3.3 km. The gravity wave associated momentum fluxes
show that long period gravity waves carry more momentum flux than the
short period waves and this is presented.
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