A thesis submitted to Manonmaniam Sudaranar University in partial fulfilment of the requirements for the award of degree of Ph.D. in physics under guidance of Dr. Manohar Lal.The present thesis work mainly focuses on the following areas : *Identification of signatures of long period Slow Kelvin waves in the mesospheric altitudes *Study of planetary normal modes in the northern and southern low latitude MLT region and its response to zonal circulation *Investigation of climatology and inter-annual variability of wave mean flow interaction in the Northern Stratosphere *Investigation of the dynamical evolution of wave 1 and wave 2 major stratospheric warming and its influence on tropical stratospheric measurement and connective activity