Inertia‐gravity waves associated with the tropical easterly jet over the Indian subcontinent during the South West Monsoon Period

Abstract

Using the MST radar located at Gadanki (13.5°N, 79.2°E) winds were measured every four hours in the troposphere and lower stratosphere during a 72‐hour period from 23 to 26 September 1997 when the tropical tropospheric easterly jet (TEJ) was present south of Gadanki with its core at a height of ∼16 km. Analysis of the radar data shows the presence of ∼56 hour oscillations (close to local inertial period of ∼51 hours) in the wind components with significant amplitudes. Examination 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 propagation) in another altitude region (8.3–10.5 km) below. This indicates the generation of Inertia Gravity Waves (IGW) in the TEJ and their propagation both upwards and downwards from the source region. The inferred vertical and horizontal wavelengths of the IGW are ∼0.7 and ∼75 km respectively in the stratosphere and ∼1 and ∼143 km respectively in the troposphere.