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Ann. Geophys., 19, 985-990, 2001
www.ann-geophys.net/19/985/2001/
© European Geosciences Union 2001
Seasonal variation of equatorial wave momentum fluxes at Gadanki (13.5° N, 79.2° E)
M. N. Sasi and V. Deepa
Space Physics Laboratory Vikram Sarabhai Space Centre Trivandrum-695022, India
Abstract. The vertical flux of the
horizontal momentum associated with the equatorial Kelvin and Rossby-gravity
waves are estimated from the winds measured by the Indian MST radar located at
Gadanki (13.5° N, 79.2° E) during September 1995 to August 1996 in the
tropospheric and lower stratospheric regions for all four seasons. The present
study shows that momentum flux values are greater during equinox seasons than
solstices, with values near the tropopause level being
16 × 10-3, 7.4 × 10-3, 27 × 10-3 and 5.5 ×
10-3 m2 s-2 for Kelvin waves and 5.5 × 10-3,
3.5 × 10-3, 6.7 × 10-3 and 2.1 × 10-3 m2
s-2 for RG waves during autumnal equinox, winter, vernal equinox and
summer seasons, respectively. Using these momentum flux values near the
tropopause level, acceleration of the mean flow in the stratosphere up to a 29
km height were computed following Plumb (1984), by considering the wave-meanflow
interaction and the deposition of the momentum through the radiative
dissipation of the waves. A comparison of the estimated mean-flow acceleration
in the stratosphere compares well, except at a few height levels, with the
observed mean-flow accelerations in the stratosphere derived from the
radiosonde data from a nearby station.
Key words. Meteorology and
atmosphenic dynamics (tropical meteorology; waves and tides)
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