Gravity wind

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gravity wind

(Also called drainage wind.) A wind resulting from cold air running or flowing down a slope, caused by greater air density near the slope than at the same altitude some distance horizontally from the slope.

Generally used when cold air is locally generated by a chilled slope surface during periods of weak synoptic or other larger-scale winds, as with katabatic or drainage winds. Slopes can be gentle as found over rolling topography or into river valleys, or steep as on mountains or mountain ranges. Although usually applied to smaller (individual slope) scale flows, the term is occasionally used to include fall winds, or air advected from a cold source region elsewhere, then spilling over and accelerating down a slope, as with a bora or a cold front passage over orography.
See downslope wind.