An anabatic wind, from the Greek anabatos, verbal of anabainein meaning "moving upward", is a warm wind which blows up a steep slope or mountain side, driven by heating of the slope through insolation. It is also known as upslope flow. These winds typically occur during the daytime in calm sunny weather. A hill or mountain top will be radiatively warmed by the Sun which in turn heats the air just above it. Air at a similar altitude over an adjacent valley or plain does not get warmed so much because of the greater distance to the ground below it.