The winds that move from cold upland areas into lower elevations under the influence of gravity are described as

 The winds that move from cold upland areas into lower elevations under the influence of gravity are described as  katabatic winds. They are also called downslope winds, or gravity winds.
These winds carry high-density air from a higher elevation (mountains, plateaus, and hills )down a slope under the force of gravity. The katabatic winds occur at night, when the highlands radiate heat and are cooled.