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Ann. Geophys., 19, 1019-1025, 2001
www.ann-geophys.net/19/1019/2001/
© European Geosciences Union 2001
Turbulence characteristics in the tropical mesosphere as obtained by MST radar at Gadanki (13.5° N, 79.2° E)
M. N. Sasi and L. Vijayan
Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum 695022, India
Abstract. Turbulent kinetic energy
dissipation rates (ε) and eddy diffusion coefficients (Kz)
in the tropical mesosphere over Gadanki (13.5° N, 79.2° E), estimated from
Doppler widths of MST radar echoes (vertical beam), observed over a 3-year
period, show a seasonal variation with a dominant summer maximum. The observed
seasonal variation of ε and Kz in the
mesosphere is only partially consistent with that of gravity wave activity
inferred from mesospheric winds and temperatures measured by rockets for a
period of 9 years at Trivandrum (8.5° N, 77° E) (which shows two equinox and
one summer maxima) lying close to Gadanki. The summer maximum of mesospheric
ε and Kz values appears to be related to the
enhanced gravity wave activity over the low-latitude Indian subcontinent during
the southwest monsoon period (June – September). Both ε and Kz
in the mesosphere over Gadanki show an increase with an increase in height
during all seasons. The absolute values of observed ε and Kz
in the mesosphere (above ~80 km) does not show significant differences from
those reported for high latitudes. Comparison of observed Kz values
during the winter above Gadanki with those over Arecibo (18.5° N, 66° W)
shows that they are not significantly different from each other above the ~80
km altitude.
Key words. Meteorology and
atmospheric dynamics (middle atmosphere dynamics; tropical meteorology; wave
and tides)
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