The direction and speed of the winds are controlled by the combination of the following factors:
i. Pressure gradient force: The difference in the atmospheric pressure produces a force. The pressure gradient is strong where the isobars are close to each other and is weak where the isobars are apart. This is the driving force and wind moves from high pressure to low pressure.
ii. Frictional force: The frictional force is present near the surface. The irregularities of the earth’s surface causes friction and obstructs the winds and influence their speed and direction. Over the sea surface, the friction is minimal.
iii. Coriolis force: The rotation of the earth about its axis affects the direction of the wind. This force is called the Coriolis force. Due to the Coriolis effect or force the winds are deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
iv. Centripetal acceleration: Due to the inward acceleration of air towards the centre of rotation on the rotating earth, it is possible for the air to maintain a curved path about a local axis of high or low pressure. It is known as centripetal acceleration.
