local air current that blows up a hill or mountain slope facing the Sun. During the day, the Sun heats such a slope (and the air over it) faster than it does the adjacent atmosphere over a valley or a plain at the same altitude. This warming decreases the density of the air, causing it to rise. More air rises from below to replace it, producing a wind. An anabatic wind may often attain a velocity of more than 6 metres per second (about 13 miles per hour).