Characteristics of tropospheric biennial oscillation and its possible association with the stratospheric QBO

Abstract

Signals of oscillation with periods ranging from 20 to 32 months are found in the tropospheric temperature over the near-equatorial Indian station, Thumba (8° 23' N, 76° 52' E). The phase of this Tropospheric Biennial Oscillation (TBO) in temperature does not vary with height from surface to the level of tropopause and is associated with the intensity of the Indian monsoon rainfall. A quasi-biennial oscillation (QBO) signal is seen in the lower stratosphere. Marked differences in amplitude of QBO and TBO are noticed between the two decades 1971-81 and 1982-92. During the first decade the downward propagating phase of QBO is disturbed in the 18-23 km altitudes. The QBO in zonal wind, however, has neither inter decadal variability nor disturbances.