Long Period Waves in the Upper Troposphere & Lower Stratosphere over the Indian Region

328-334Long period waves in the upper troposphere and lower stratosphere in the Indian region have been identified using monthly mean data on the zonal and meridional winds and temperature over seven stations in the latitude range of 8-28°N. Four members of the wave family, viz. 2 month, 6 month, 12 month and 20-40 month periodicities, have been identified. The 2 month wave is masked by the more dominant Kelvin wave. The 6 month wave is confined to the equatorial stratosphere. The tilt of the line of maximum amplitude suggests transport of energy from the upper troposphere to lower stratosphere. The amplitude of the annual wave is a maximum below the tropopause. The prominent maximum near 200 mb, between 20 and 25°N is associated with the subtropical westerly jet. The quasi-biennial oscillation (QBO) present in the zonal wind and temperature is confined to 3D-month period. From the downward tilt from the equator to the sub-tropics in the line of maximum amplitude, it is inferred that the QBO originates in the equatorial stratosphere and travels to the upper troposphere over the subtropical latitudes