Tidal winds at mesopause altitudes over Arecibo (18 deg N, 67 deg W), 5-11 April 1989 (AIDA '89)

A tidal analysis of the imaging Doppler interferometer scattering point parameter data at upper mesosphere-lower thermosphere altitudes (70-110 km) is presented, on the basis of the procedure developed by Groves (1959), over the interval April 5-11, 1989 at Aercibo as part of Project AIDA. This analysis reveals a typical equatorial easterly circulation, with mean meridional circulation becoming significant only above 96 km. A periodogram analysis shows the diurnal tide to be the most significant feature of the wind field at these altitudes, with zonal amplitudes up to some 50 m/s and meridional amplitudes approximately half this value. The semidiurnal tide is well developed in both zonal and meridional directions only above 96 km. Both 8- and 6-hr components become significant above 100 km, the 6-h component being as strong as both the 24- and 12-h tides at 100 km.