Coordinated global radar observations of tidal and planetary waves in the mesosphere and lower thermosphere during January 20-30, 1993

A multi-instrument global campaign involving incoherent scatter, medium frequency, and meteor wind radars was conducted during the period of January 20-30, 1993, to study the dynamics of the mesosphere and lower thermosphere. Data obtained from 15 radar stations covering a wide latitude range have been used to determine the global distribution of planetary and tidal waves during this 10-day campaign. Spectral analysis of the neutral winds measured by the radars in the altitude range from 80 to 130 km indicates the existence of a strong 48-hour wave near 90 km at latitudes between 40 degrees N and 40 degrees S that is present up to 108 km at 18 degrees N. The semidiurnal tide is large at middle and high latitudes near 90 km and is predominant above 110 km, while the diurnal tide is observed to be particularly important in the upper mesosphere near 40 degrees latitude. A least squares fit to the radar data is performed to obtain the amplitudes and phases of the tidal and 48-hour waves. Comparison with National Center for Atmospheric Research thermosphere-ionosphere-mesosphere general circulation model shows that the predictions from the model agree reasonably well with the observed global morphology of tidal wave amplitudes.