Editing Atmospheric circulation (section)

=== Polar cell ===
{{Main|Polar vortex|Polar easterlies}}
The '''polar cell''' is a simple system with strong convection drivers. Though cool and dry relative to equatorial air, the air masses at the [[60th parallel (disambiguation)|60th parallel]] are still sufficiently warm and moist to undergo [[convection]] and drive a [[thermal loop]]. At the 60th parallel, the air rises to the tropopause (about 8&nbsp;km at this latitude) and moves poleward. As it does so, the upper-level air mass deviates toward the east.   When the air reaches the polar areas, it has cooled by radiation to space and is considerably denser than the underlying air. It descends, creating a cold, dry high-pressure area. At the polar surface level, the mass of air is driven away from the pole toward the 60th parallel, replacing the air that rose there, and the polar circulation cell is complete. As the air at the surface moves toward the equator, it deviates westwards, again as a result of the [[Coriolis effect]]. The air flows at the surface are called the polar easterlies, flowing from northeast to southwest near the north pole and from southeast to northwest near the south pole.

The outflow of air mass from the cell creates [[harmonic|harmonic wave]]s in the atmosphere known as [[Rossby wave]]s. These ultra-long waves determine the path of the polar [[jet stream]], which travels within the transitional zone between the [[tropopause]] and the [[Ferrel cell]]. By acting as a heat sink, the polar cell moves the abundant heat from the equator toward the polar regions.

The polar cell, terrain, and [[katabatic winds]] in Antarctica can create very cold conditions at the surface, for instance [[lowest temperature recorded on Earth|the lowest temperature recorded on Earth]]: −89.2&nbsp;°C at [[Vostok Station]] in Antarctica, measured in 1983.<ref>{{cite web|url=http://www.antarctica.ac.uk/met/momu/International_Antarctic_Weather_Forecasting_Handbook/2.1_The%20physical%20environment%20of%20the%20Antarctic.php|title=The physical environment of the Antarctic|publisher=British Antarctic Survey (BAS)}}</ref><ref>{{cite web|url=http://www.discoveringantarctica.org.uk/alevel_2_2.html |title=Regional climate variation and weather |publisher=RGS-IBG in partnership with BAS |url-status=dead |archive-url=https://web.archive.org/web/20150306052337/http://www.discoveringantarctica.org.uk/alevel_2_2.html |archive-date=2015-03-06 }}</ref><ref>{{cite web|url=http://www.scientificamerican.com/article/oymyakon-the-coldest-town/|title=Welcome to the Coldest Town on Earth|publisher=Scientific American|year=2008}}</ref>