q Air molecules in the parcel (or the balloon)
have to use their kinetic energy to
expand the parcel/balloon.
qTherefore, the
molecules lost energy and slow down their motions
q è The temperature of the
air parcel (or balloon) decreases with elevation. The lost
energy is used to increase the potential energy of air
molecular.
qSimilarly when the air
parcel descends, the potential energy of air molecular is
converted back to kinetic energy.
q è Air temperature rises.