Heat is transferred through the rod and eventually the whole rod is hot. Air becomes buoyant when air near the ground becomes less dense than air that surrounds it. The upward force of the heavy air forces the lighter air upward. Air moves in from the sides to replace the displaced air. Air that is more dense than surrounding air descends toward the ground.
Heat is distributed throughout the troposphere by conduction and convection.
Radiation - energy that propagates through free space or through a material medium in the form of electromagnetic waves. The quantity and quality of radiation is described by the amplitude and the wavelength of the electromagnetic waves.