Definition

Air flow travelling up a facing slope of an orographic surface (eg. hill, mountain).

Description

Anabatic winds are mainly created by ultraviolet solar radiation heating up the lower regions of an orographic area (i.e. valley walls). Due to its limited heat capacity, the surface heats the air immediately above it by conduction. As the air warms, its volume increases, and hence density and pressure decreases. The air becomes relatively buoyant and rises up the orographic slope (orographic lift), resulting in the anabatic flow (or wind).

The relatively colder air is displaced, part of it travels downwards to “replenish” the valley floor, and the process of heating by conduction may begin anew.