NCERT Notes: Forces Affecting Velocity And Direction Of Wind [Geography Notes For UPSC]

NCERT notes on important topics for the UPSC Civil Services Exam. These notes will also be useful for other competitive exams like banking PO, SSC, state civil services exams and so on. This article talks about the Forces Affecting the Velocity and Direction of Wind.

Forces Affecting the Velocity and Direction of Wind
  • The air in motion is called wind.
  • The wind blows from high pressure to low pressure.
  • The wind at the surface experiences friction.
  • The rotation of the earth also affects the wind movement.
  • The force exerted by the rotation of the earth is known as the Coriolis force.
  • Therefore, the horizontal winds near the Earth’s surface respond to the combined effect of three forces:
    • The Pressure Gradient Force
    • The Frictional Force
    • The Coriolis Force

Pressure Gradient Force
  • The differences in atmospheric pressure generate a force.
  • The rate of change of pressure with regard to distance is known as the pressure gradient.
  • The pressure gradient is weak where the isobars are distant and strong where the isobars are close by to each other.

Frictional Force
  • It impacts the speed of the wind.
  • The friction is maximum at the surface and minimal over the sea surface.
  • The influence of frictional force usually stretches up to an elevation of 1 – 3 km.

Coriolis force
  • The rotation of the earth about its axis affects the direction of the wind and this force is called the Coriolis force.
  • It is directly proportional to the angle of latitude.
  • It deflects the wind to the left direction in the southern hemisphere and the right direction in the northern hemisphere.
  • The deflection is more when the wind velocity is high.
  • It is maximum at the poles and is absent at the equator.
  • The force acts perpendicular to the pressure gradient force.
  • The pressure gradient force is perpendicular to an isobar.
  • The higher the pressure gradient force, the more is the speed of the wind and the larger is the deflection in the direction of wind happens.
  • As a result of these two forces functioning perpendicular to each other, in the low-pressure areas the wind blows around it.
  • The Coriolis force is zero at the equator and the wind blows perpendicular to the isobars.

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