Tidal wind oscillations in the tropical lower atmosphere as observed by Indian MST Radar

Diurnal tidal components in horizontal winds measured by MST radar in the t roposphere and lower stratosphere over a tropical station Gadanki (13.5 deg rees N, 79.2 degrees E) are presented for the autumn equinox, winter, verna l equinox and summer seasons. For this purpose radar data obtained over man y diurnal cycles from September 1995 to August 1996 are used. The results o btained show that although the seasonal variation of the diurnal tidal ampl itudes in zonal and meridional winds is not strong, vertical phase propagat ion characteristics show significant seasonal variation. An attempt is made to simulate the diurnal tidal amplitudes and phases in the lower atmospher e over Gadanki using classical tidal theory by incorporating diurnal heat s ources, namely, solar radiation absorption by water vapour, planetary bound ary layer (PBL) heat flux, latent heat release in deep convective clouds an d short wave solar radiation absorption by clouds. A comparison of the simu lated amplitudes and phases with the observed ones shows that agreement bet ween the two is quite good for the equinox seasons, especially the vertical structure of the phases of the meridional wind components.