Illustration showing surface winds and vertical wind circulation cells on a rotating Earth globe. In the tropics, the winds flow from east to west (tropical easterlies, red arrows), forming Hadley cells. At higher latitudes, the winds flow from west to east and are called prevailing westerlies (blue arrows), forming mid-latitude cells (Ferrel cells). In the polar regions, cooler air sinks back towards lower latitudes (green arrows), forming polar cells. These patterns are caused by the Coriolis effect, where winds in each hemisphere are deflected in opposite directions by Earth's rotation.