Radiosonde studies of internal waves in the southern near-equatorial atmosphere of the Earth

Abstract

Radiosonde measurement data of the wind speed, conducted on 28 February and on 15 November 2007, have been used for the internal gravity waves (IGWs) identification and determination of their parameters in the Earth’s lower stratosphere over Cocos Islands (coordinates: latitude –12.04°S and longitude –96.90°E). A wind speed hodograph analysis has shown that observed fluctuations are wave-induced while the wave energy propagates upwards. Using the results of a wind speed hodograph analysis, dispersion equation and polarization relations, we have obtained the magnitudes of key IGW characteristics such as the intrinsic frequency, amplitudes of vertical and horizontal perturbations of the wind speed, vertical and horizontal wavelengths, intrinsic vertical and horizontal phase (and group) speeds, wave kinetic, potential and total energy. An original method for determining the wave ground-based frequency and azimuthal angle of IGW propagation in the Earth’s atmosphere has been proposed. Application of the developed method to radiosonde measurements, conducted on 28 February 2007, has given a possibility to establish that the wave ground-based frequency is equal to 14.0· 10−4 rad/s and it corresponds to the actual wave period T=1.25 hours.