In the realm of atmospheric sciences, the vertical air motion in any region dictates the structure and dynamics of that region. Importantly in the lower part of the atmosphere, wide spread deterioration and improvement of weather is usually caused by the vertical air motion. Adiabatic cooling due to upward motion leads to formation of clouds and adiabatic warming due to downward motion leads to dissipation of clouds. Thus vertical air motion plays a vital role in controlling the day to day weather. Also the information of convective updrafts/downdrafts is crucial for aviation industry and also for rocket launches. The direct measurements of vertical air motion were not possible until the advent of wind profilers. Realizing the importance of vertical air motion in the tropical atmosphere, the present thesis brings out unique results on the mean structure and variability of vertical velocity during fair-weather and convection using long term data (10 years) from Indian Mesosphere...