Turbulence characteristics in the tropical mesosphere as obtained by MST radar at Gadanki (13.5 degrees N, 79.2 degrees E)

Turbulent kinetic energy dissipation rates (epsilon) and eddy diffusion coe fficients (K-z) in the tropical mesosphere over Gadanki (13.5 degrees N, 79 .2 degrees E), estimated from Doppler widths of MST radar echoes (vertical beam), observed over a 3-year period, show a seasonal variation with a domi nant summer maximum. The observed seasonal variation of epsilon and K-z in the mesosphere is only partially consistent with that of gravity wave activ ity inferred from mesospheric winds and temperatures measured by rockets fo r a period of 9 years at Trivandrum (8.5 degrees N, 77 degrees E) (which sh ows two equinox and one summer maxima) lying close to Gadanki. The summer m aximum of mesospheric epsilon and K-z values appears to be related to the e nhanced gravity wave activity over the low-latitude Indian subcontinent dur ing the southwest monsoon period (June - September). Both epsilon and K-z i n the mesosphere over Gadanki show an increase with an increase in height d uring all seasons. The absolute values of observed epsilon and K-z in the m esosphere (above similar to 80 km) does not show significant differences fr om those reported for high latitudes. Comparison of observed K-z values dur ing the winter above Gadanki with those over Arecibo (18.5 degrees N, 66 de grees W) shows that they are not significantly different from each other ab ove the similar to 80 km altitude.