Wind is a meteorological phenomenon in which there is a flow of air in the atmosphere, called wind. It happens when the sun heats the ground or ocean or water to a temperature higher than that of adjacent regions.
This difference in temperature generates thermal currents, i.e., an uneven heating of the ground and water results in different temperatures between two points in the atmosphere above these surfaces.
The warmest point creates changes, i.e., rises because it is warmer and expands, while there is less dense air above it that sinks to take its place.
These rising and sinking air masses undergo a circular movement taking place from hot to cold regions. As a result, a current of cooler air flows from high pressure areas towards low pressure areas.
In addition, rotation of the earth also affects the wind movement. The force exerted by the rotation of the earth is known as the Coriolis force.
Thus, the horizontal winds near the earth surface respond to the combined effect of three forces — the pressure gradient force, the frictional force and the Coriolis force. In addition, the gravitational force acts downward. Pressure Gradient Force
Frictional Force: It affects the speed of the wind.It is greatest at the surface and its influence generally extends upto an elevation of 1 3 km. Over the sea surface the friction is minimal.
Coriolis Force: The rotation of the earth about its axis affects the direction of the wind. This force is called the Coriolis force after the French physicist who described it in 1844.It deflects the wind to the right direction in the northern hemisphere and to the left in the southern hemisphere.
The deflection is more when the wind velocity is high. The Coriolis force is directly proportional to the angle of latitude. It is maximum at the poles and is absent at the equator.
The Coriolis force acts perpendicular to the pressure gradient force. The pressure gradient force is perpendicular to an isobar.
The wind circulation at the earth’s surface around low and high on many occasions is closely related to the wind circulation at higher level. Generally, over low pressure area the air will converge and rise.
