The movement of air in the horizontal direction is called wind.
- The wind is under influence of the pressure gradient force (PGF), the frictional force and the Coriolis force.
PRESSURE GRADIENT FORCE (PGF)
- It is the rate of change of pressure with respect to distance
- It is perpendicular to the isobars (parallel lines connecting same atmospheric level). Hence, PGF is strong where the isobars are close to each other and is weak where the isobars are apart.
- If PGF is high, wind speed will be more.
- It is due to friction between the features (natural and man-made both) of the Earth and wind.
- It affects the speed of the wind.
- It is greatest at the surface and its influence generally extends
- Over the sea surface, the friction is minimal.
The rotation of the earth about its axis affects the direction of the wind.
This force is called the Coriolis force (a pseudo force exerted on a moving object i.e. wind by the rotating non inertial frame observer).
It has a role only in the direction of the wind. In doing so, it deflects the wind in the right direction in the northern hemisphere and to the left in the southern hemisphere.
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