A study of diurnal tidal oscillations in horizontal winds using Indian mesosphere-stratosphere-troposphere radar located at Gadanki (13.5 ¿N, 79.2 ¿E) shows that during autumnal equinox season diurnal amplitudes of 1--2 m s-1 of horizontal winds prevail in the troposphere. The vertical structure of amplitudes and phases indicate a vertical wavelength of ~3 km in the lower troposphere and ~6 km in the upper troposphere. A comparison of these amplitudes and vertical wavelengths with results from theoretical tidal models suggests that these oscillations in the lower troposphere are manifestation of nonmigrating diurnal tidal oscillations excited by eddy heat flux in the planetary boundary layer and those in the upper troposphere excited by latent heat release in deep convective clouds. However, nonmigrating diurnal tidal modes generated by solar radiation absorption by water vapor and clouds in the troposphere cannot be ruled out. ¿ 1998 American Geophysical Union