137-143Thermal convection has been observed to be a daytime atomospheric phenomenon. The thermal plumes have been recorded with an echosonde over Punjabi University, Patiala. These plumes have been observed up to an altitude of one kilometer of the planetary boundary layer. Detailed studies of the growth and dissipation, occurrence, height, diameter and velocity of the plumes and their effecton microwave communication have been made. They have periods ranging from 1 to 20 min and the diameter varies from 0.2 to 2.40 km, while the vertical velocities vary from a fraction of a metre to 2 meters per second. It is recommended that the pollutants should be released into the atmosphere only under the plume conditions so as to minimize the environmental pollution