The semidiurnal tide for individual nights derived consistently from O 2 and OH intensities and temperatures

Abstract

The semidiurnal tide is studied with 159 special cases from the large airglow database acquired at El Leoncito (31.8ºS, 69.3ºW). These cases correspond to nights which exhibit similar periods in the temperature and intensity variations of the OH(6-2) and O 2 b(0–1) emissions. We find that all the periods (except one) are between 9 and 15.5 h. The phase distributions of these cases are narrow enough to ensure the identification as the semidiurnal tide, and their progression with altitude is consistent with downward phase propagation. The mean temperature amplitudes are large for both emissions. We obtain new values for Krassovsky's ratio including its phase. The vertical wavelength is determined independently for each emission using the relation suggested by the Hines and Tarasick theory. Mean vertical wavelengths derived for O 2 are longer than those for OH. The longest monthly mean wavelengths are observed from May to August. The mean ratio of temperature amplitudes between the two emissions corresponds to moderate wave attenuation during the upward propagation of the tide.