An air mass, originating in latitudes 50–70°, which may have a maritime or continental source. Maritime polar air has high relative humidity, is warmed in its passage towards the equator or over warmer seas, and becomes unstable. Continental polar air is stable in its source region and is associated with very cold surface conditions in winter (e.g. Siberian air moving across Europe).
Subjects: Earth Sciences and Geography — Ecology and Conservation.