Atmosphere Contents

5. General Circulation

Polar fronts form at high-mid-latitudes

At latitudes of 45-60 the mild air, which as travel north from the descending branch of the Hadley cell, meets cold area travelling south from the poles.These two air masses are of contrasting temperature which do not readily mix and are therefore separated by a boundary. This is termed the polar front, a zone of low pressure, the subpolar low, where surface air converges and rises and storms develop. Some of this rising air returns at high altitudes to the horse latitudes, where it sinks back to the surface near the subtropical high. Cellular flow, commonly known as the Ferrel cell, is completed when surface air from the horse latitudes flows poleward towards the polar front.

The general circulation of the atmosphere where the polar front exists between 45°-60° latitude

Why do polar fronts form at mid-latitudes?