Anabatic and Katabatic winds are winds that flow up or down a hill slope.
Similar to the sea breeze, as the sun heats a hill side through solar radiation, the air on the hill warms and begins to rise. As it rises, the air below the hills will flow up the hill side to replace the rising air. The Pressure Gradient Force here can be quite strong but the Anabatic winds are usually quite weak since they have to flow upwards against the force of gravity.
The opposite to Anabatic Winds are Katabatic Winds which flow down a slope due to gravity. Overnight, the air on a hilltop is cooled through conduction with the cold land. As the air cools, density increases and gravity forces it down the hillside, creating a flow of cold air blowing down the slope.
Katabatic winds often increase in strength as the temperature continually drops overnight and the wind is usually strongest around sunrise.