Convection - heat that is transferred by moving air or water. The process which involves a rising or sinking air parcel and the temperature changes associated with that motion. As an air parcel rises it moves into an area of lower pressure aloft. This lower pressure causes the air parcel to expand. The expansion allows more room for the air molecules inside the parcel to move about.
More room means less collisions between the molecules.
Less KE means cooler temperatures. This higher pressure causes the air parcel to compress. The compression allows less room for the air molecules inside the parcel to move about. Less room means more collisions between the molecules. More KE means warmer temperatures.