Also, air is cooler as we go up in altitude as a result of adiabatic cooling. Ariel - The earth's atmosphere is rather transparent to radiation.
Atmospheric heating is largely the result of conduction.
There are two terms - standard lapse rate and adiabatic lapse rate. Standard lapse rate is likely what you are referring to and is measured by traveling up through the atmosphere. Adiabatic lapse rate requires a lifting force which causes a parcel of air to move up and reduce pressure causing a drop in temperature. If there is no lifting force, there is no adiabatic cooling. I'll try to simplify the radiation balance equation as much as possible, and use percentages rather than the actual numerical values of the radiation.