Global winds refer to the pattern of air movement all around the globe, and they result from the fact that the Earth receives unequal heating from the sun. Not only does the tilt of the Earth's axis mean that different parts of the planet receive disparate amounts of sunlight, but the oceans and lands also heat at different rates. The imbalance in temperature makes heat move toward the poles, both in the wind and in ocean currents. When horizontal variances in air pressure take place as a result, wind occurs.
While local wind patterns appear to change from day to day at times, there is a global pattern of winds called the "general circulation." The surface winds that move across the hemispheres are split up into three different wind belts. The polar easterlies appear between 60 and 90 degrees of latitude in both hemispheres, moving southwest in the Northern Hemisphere and northwest in the Southern Hemisphere. At the 60-degree line is a subpolar low pressure area, and then between 30 and 60 degrees of latitude come the prevailing westerlies, moving northeast in the Northern Hemisphere and southwest in the Southern Hemisphere. Between 30 degrees and an area near the equator called the Intertropical Convergence Zone are the tropical easterlies, moving in the same direction as the polar easterlies.