Ferrel cell
The Ferrel cell or Mid Cell was proposed to account for mid latitude westerly winds as statistically averaged circulation where air converges at low altitudes and ascends along the boundaries of cool polar air and warm subtropical air around between 60 and 70 degrees north and south. It was proposed by William Ferrel in 1856 some 100 years after the proposed Hadley cell.
This type of air circulation occurs near the latitude of the UK and is the reason why the UK has such varying weather patterns. The circulation of this cell is impacted by the return flow of high altitude air around the tropics, where it joins sinking air from the Hadley cell. The Ferrel cell moves in opposite directions to that of the Hadley and Polar cells. The Polar cells are the weakest circulation cells which extend 60 to 70 degrees north and south, sinking over the highest latitudes and flowing out towards the lower latitudes at the surface. The Hadley cell extends from the equator to between 30 and 40 degrees North and South.
Atmospheric circulation around the earth is impacted by all three different cells (and jet streams) along with what is known as the Corriolis effect, which occurs a result of the earth’s spin, and describes why air moves in a certain direction around certain areas of low pressure.
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