but at the poles, earth's surface is much closer to the axis of rotation, so it moves more slowly (~ half the speed of equator)
these differences in speed of rotation cause additional atmospheric cells and deflections:
get a pair of circulation cells on either side of equator (Hadley cells); at mid-latitudes, air descending at 30° latitude turns poleward and is joined by air returning from the north/south (Ferrel cells); at the poles air at the surface blows towards the equator and by 50°/60° latitude, it has taken up enough heat to rise -- however because of density differences it can't mix with air in Ferrel cells, so it turns poleward, creating a polar cell