The rate of decrease of temperature with increasing altitude in the atmosphere. If heat is neither gained nor lost from the air parcel under consideration, then the lapse rate is said to be adiabatic and the energy to expand the volume of the parcel or rising air comes from the kinetic energy of the gas molecules in that parcel. The expansion of the parcel causes these molecules net kinetic velocity to decrease and this is equivalent to cooling the air. In dry air the dry adiabatic lapse rate is about 9. 8 C/km (the sign is traditionally positive although the temperature is decreasing with altitude). See Foehn. In moist air the release of latent heat by condensation of the contained moisture makes the lapse rate lower,