Geography Answer Writing Practice 2018 - Week 3 - Question 3

90 Days Geography Answer Writing Practice Question 1 for 28-Nov-2018

Instructions for Writing Answer

1. Write your answers in the comment section.


2. Experts will provide their feedback in reply.

3. Model Answers will be uploaded on this page the next day.

4. Rectify your mistakes and progress further.

5. All the Best.

28-Nov-2018 - Question 1

Discuss the forces that govern the air movement on the Earth's surface. 20 marks.
For Question 2 - Click Here

Model Answer

Air movement on the earth’s surface is both horizontal and vertical. Horizontal movement is classified as wind movement while vertical motion leads to formation of convectional currents. The factors that govern the movement of air on the Earth's surface are:



1. Pressure gradient - Air moves from areas of high pressure to areas of low pressure. The pressure gradient is created to the difference in insolation received on the earth’s surface. This has led to the creation of pressure belts on a global scale.  The equatorial regions receive the maximum insolation due to which the air is warmed and a low pressure region is created. This low pressure region pulls air inwards from the sub-tropical high pressure region. This phenomenon occurs at meso and micro levels with low pressure regions being attracting regions and high pressure regions being the regions where there is outward flow of air. Pressure differences and thermal expansion of air also causes vertical currents of air.

2. Coriolis effect - It refers to the deflection of moving air due to the rotation of the Earth. The Coriolis effects becomes less if the air moves slowly. So the air near the surface of the Earth does not move directly parallel between the areas of high and low pressures. It gets deflected outward from a high pressure and inward toward a low pressure. So low pressures fill and high pressures subside. This effect is more pronounced and clearly visible in the circular motion of cyclones.
3. Friction - This has an impact on the movement of the boundary layer or the air which is in contact with the Earth. It acts as a barrier for the wind movement.  It is minimal over sea but can have high value over rough terrain.
4. Centripetal acceleration - It acts on air that is flowing in a circular manner. It creates a force acting perpendicularly to the motion of the wind and inward toward the centre of rotation.

Note: There is no template for a correct UPSC answer, the model answer is only for your reference

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