1-14The climatalogies of quasi 2-day and 16-h wind oscillations obtained from the Meteor Wind Radar observations at Trivandrum (8°N, 77°E) are presented. The quasi 2-day oscillation amplitude is 20-30 ms-1, and during some months it is as large as 60 ms-1 at some altitudes. Amplitudes summer are small in contrast to largest summer amplitudes reported from mid-latitudes, the amplitude and phase profiles indicate the simultaneous presence of two wave modes; the stronger mode has large vertical wavelength (> 100 km) and the weaker mode has shorter vertical wavelength of 16 km, consistently during all the months. The amplitudes of both the modes are comparable in the NS and EW winds. The observed vertical wavelength of both the modes was found not to agree with that of wave number 3 Rossby wave, which is identified as the most probable wave mode in mid-latitudes. The 16-h oscillation amplitudes are significant during all the months over Trivandrum. The two significant wave modes of the 16-h oscillation identified could be of the products of interaction between the two quasi 2-day oscillation modes and the 24-h and/or 12-h tidal modes in the mesopause and above, reported earlier at Trivandrum
