Spectral results from a sounding of temperature and wind velocity between 11.9 and 23.1 km performed with an open type stratospheric balloon near the Andes Mountains, are reported. The use of this kind of balloons and high performance instruments, allowed to attain better spatial resolution (around 2.5 meters during the descent) than previous results and other sounding techniques. This high resolution permitted to study the complete interval of altitude data in three consecutive subintervals (below, around and above the tropopause). Each of these subintervals shows different saturation characteristics. Some differences have been found with the general pattern of power spectal densities reported by different theories. A large amplitude wave of around 1.8 km and possibly originated in the mountain relief, is clearly observed in the temperature, vertical and shear wind velocity components. ¿ American Geophysical Union 1994