Observational Evidence of Internal Inertia-Gravity Waves in the Tropical Stratosphere

Abstract Twenty-nine highly accurate wind profiles up to 30 km obtained during four days of the GARP Atlantic Tropical Experiment (GATE) by tracking vertically ascending balloons with radar are presented and analyzed. The existence of short, vertical wavelength easterly waves propagating upward in the tropical stratosphere, as suggested by a quick look at the profiles, is demonstrated and the wave characteristics are determined. The period of the waves is determined from the power spectra of the u (eastward) and v (north-ward) components at different heights, computed by the lag correlation method and from the rotary spectra computed by the maximum entropy method (35 h). Clockwise rotation of wind vector with time at various levels indicates westward propagation of the phase relative to the medium. Cross spectra between different levels are computed and phase differences demonstrate the downward propagation of phase. From the chronological sequence of u and v profiles, the vertical profile of vertical pha...