Earth rotation effects wind direction for two reasons: first, the Earth rotates eastward; and second, the velocity at which the Earth turns is relative to the position of latitude on the Earth (the velocity at the poles is basically zero while the velocity at the Equator is much faster). As a result, if a cannon was fired from the North Pole towards the Equator, the cannon would appear to veer off course, landing to the left of the target. Similarly, winds that blow across the surface from the east to the west (or any direction) will change direction as they moves across the surface of the Earth. This concept of the effects of Earth rotation is known as the Coriolis Effect.
Air moves from areas of low pressure to areas of high pressure. When you open a can of soda or tennis balls, the pressurized air rushes out of the can into the lower-pressure atmosphere, creating the audible whooshing sound. On a non-rotating Earth, a circular high-pressure area would push air directly from the center of the high-pressure area, creating equally spaced rays. Because the Earth rotates, however, air flows clockwise around highs and counterclockwise around lows in the Northern hemisphere.
Wind speed generally increases in the stratosphere and decreases near the Earth's surface. This is because wind experiences friction from hills, trees, buildings and other features of the Earth's surface. The varying levels of friction also influence wind direction, because these features create paths of less or more resistance, resulting in changes in wind direction (wind must blow over or around features).
