DYANA CAMPAIGN RESULTS ON LONG-PERIOD ATMOSPHERIC WAVES OVER THUMBA AND BALASORE

The variation with altitude of the spectral amplitudes of the long per iod waves in the middle atmospheric zonal and meridonal wind over Thum ba (8.5-degrees-N, 76.9-degrees-E) and Balasore (21.5-degrees-N, 86.9- degrees-E) have shown clearly the enhanced dissipation of the atmosphe ric waves in the lower stratosphere and near the stratopause. The ampl itudes are, in general, large for the lower frequency (<0.1 cycles/day ) waves in the troposphere. While propagating through the tropopause i nto the stratosphere and above, waves with periods in the range of 5-1 0 days suffer less attenuation. The dissipation of the atmospheric wav es is found to be relatively large for frequencies below 0.1 cycles/da y. The results are compared with earlier observational studies and the oretical computations on the propagation of equatioral waves through t he middle atmosphere.