Cold, dry, and generally stable air that originates in the continental anticyclones in the northern hemisphere, primarily the Canadian and Siberian anticyclones. These are particularly strong in winter, but weaken in summer, when the source regions shrink to a relatively narrow belt in the northern part of the continents. There are no source regions in the southern hemisphere. Strong cooling at the surface leads to stable air, which combines with subsidence to produce a deep inversion, typically up to 850 hPa. When continental polar air flows out over open water, it gains in temperature and humidity, and becomes unstable maritime polar air. See also Arctic air; maritime Arctic air.
Subjects: Meteorology and Climatology — Environmental Science.