QBO influences on the variability of planetary waves in the equatorial mesopause region

MF radar observations of hourly mean zonal and meridional winds at 86 km over Tirunelveli (8.7degreesN, 77.8degreesE), India, over a period of five years (1993-1997) are utilized to study the possible influence of stratospheric quasi-biennial oscillation (QBO) on the vertical propagation of planetary-scale waves. The radiosonde winds at Singapore are used to identify the phase of the stratospheric QBO at 30 hPa. The study reflects that the interannual variability of the planetary waves may be explained partly by the direction of the stratospheric QBO winds. Limitations of the present work are: (i) the QBO cycles considered are not many and (ii) the observed waves are presumed to originate from below and propagate through the stratospheric QBO wind system.