GARY HINCKS / SCIENCE PHOTO LIBRARY GARY HINCKS / SCIENCE PHOTO LIBRARY
Global winds. Planetary model of the wind patterns observed in Earth's atmosphere, caused by the west-to-east rotation (red arrow at top) of the Earth on its axis. In the tropics, the winds flow from east to west, in what are known as tropical easterlies, or trade winds (red arrows). At higher latitudes, the winds flow from west to east and are called prevailing westerlies (purple arrows). In the polar regions, the circulation is less ordered, with the cooler air sinking back towards lower latitudes (blue arrows). This is caused by the Coriolis effect, where winds in each hemisphere are deflected in opposite directions by Earth's rotation.
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