The wind results from the large-scale movements of air masses in the air in motion. Succinctly put, wind is air in motion. These movements of air created on a global scale primarily by differential solar heating of the earth’s atmosphere. Thus, wind energy, like hydro, is also an indirect form of solar energy. Air in the equatorial regions is heated more strongly than at other latitudes, causing it to become lighter and less dense. This warm air rises to altitudes and then starts to ¥ow northward and southward toward the poles where the air near the surface is cooler. This movement stops at about 30°N and 30°S, where the air starts to cool down and sink and a return ¥ow of this cooler air takes place in the lowest layers of the atmosphere. The areas where air is descending are called the low-pressure zones. Hence, this horizontal pressure gradient forces the ¥ow of air from high to low pressure, which dictates the speed and initial direction of wind motion. Naturally, the greater the pressure gradient, the greater is the wind speed. But, as soon as wind motion is created, a de¥ective force takes place due to the rotation of the earth, which changes the direction of motion. This force is called the Coriolis force.