(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.