Inertia-gravity waves associated with the tropical easterly jet over the Indian subcontinent during the south west monsoon period

Using the MST radar located at Gadanki (13.5 degrees N, 79.2 degrees E) win ds were measured every. four hours in the troposphere and lower stratospher e during a 72-hour period from 23 to 26 September 1997 when the tropical tr opospheric easterly jet (TEJ) was present south of Gadanki with its core at a height of similar to 16 km. Analysis of the radar data shows the presenc e of similar to 56 hour oscillations (close to local inertial period of sim ilar to 51 hours) in the wind components with significant amplitudes. Exami nation of the corresponding horizontal wind vector shows clockwise rotation with altitude (upward energy propagation) in an altitude region (17.7 - 20 .8 km) above the TEJ and anticlockwise rotation (downward energy propagatio n) in another altitude region (8.3 - 10.5 km) below. This indicates the gen eration of Inertia Gravity Waves (IGW) in the TEJ and their propagation bot h upwards and downwards from the source region. The inferred vertical and h orizontal wavelengths of the IGW are similar to 0.7 and similar to 75 km re spectively in the stratosphere and similar to 1 and similar to 143 km respe ctively in the troposphere.