Global Wind Patterns
Wind is mainly the outcome of a thermodynamic principle and of the coriolis effect due to the rotation of the earth towards the east (counterclockwise). Warm air around the equator is lifted, which creates a suction effect for air masses coming from higher (or lower) latitudes. The high altitude air masse move either north or south until their temperature is low enough for them to "sink" and start to converge towards the equator. As these air masses move, the coriolis effect shift their direction. The outcome is a system of circulation known as a "cell"; three of which are between the equator and the North Pole (and vice versa for the South Pole). The most significant is the Hadley Cell from which the "Trade Winds" are the outcome.