LARGE-AMPLITUDE WAVES DETECTED WITH BALLOONS NEAR THE ANDES MOUNTAINS

Spectral results from a vertical sounding of temperature and wind velo city performed with an open stratospheric balloon in Argentina near th e Andes mountains between 12 and 25 km of altitude, are reported. The use of sonic anemometers allows for a higher resolution than in previo us experiments. The data records are studied in successive subinterval s, yielding a good spectral correlation between the ascent and the des cent around and below the tropopause. The possibilities of an orograph ic origin for large amplitude modes observed in the spectra and of wav e generation by non linear interactions between them are discussed.