The Polar Cell

Winds at the highest latitudes tend to be easterly (Figure 12.1, Figure 12.5 and Figure 12.10), which can be explained by a circulation like that of the Hadley cell. Air over the pole continually cools, becoming more dense and therefore subsides, eventually sliding down the dome of Antarctic ice. This flow is deflected westward by the powerful Coriolis effect of high latitudes, forming the south-easterlies which help form the Antarctic front between 60-65°S, where the MSLP is lower than anywhere else (Figure 1.8). Then the air is raised by frontal, disturbances which break up the front, as at the polar front. (However, the disturbances and the Antarctic front are limited to low levels only, whereas the polar front affects the entire troposphere.) Air above the Antarctic front flows back towards the pole, completing a meridional circulation called the polar cell. It is the weakest and most shallow of all three cells in each hemisphere, and covers the smallest area.

There are strong westerly winds between the Antarctic and polar fronts, with uplift at the disturbances on each side. Sometimes the two fronts temporarily combine into one.

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