Winds - Notes | Geography for UPSC 2024 (Pre & Mains) PDF Download

 Page 1


 
 
WINDS:  
? The air in motion is called wind.  
? Pressure differences force winds to flow from high pressure are to 
low pressure area. Pressure differences in turn are caused by unequal 
heating of the earth’s surface by solar radiation. 
? The wind blows from high pressure to low pressure.  
? Winds balance uneven distribution of pressure globally. 
? Winds help in transfer of heat, moisture etc. from one place to 
another. 
 
FACTORS AFFECTING THE WIND VELOCITY  
 
PRESSURE GRADIENT FORCE  
? The rate of change of pressure with respect to distance is the pressure 
gradient.  
? The pressure gradient is strong where the isobars are close to each 
other and is weak where the isobars are apart. 
? The pressure-gradient force is the force that results when there is a 
difference in pressure across a surface. 
FRICTIONAL FORCE  
? The irregularities of the earth’s surface offer resistance to the wind 
movement in the form of friction. 
? It is greatest at the surface and its influence children extends upward 
elevation of 1 - 3 kilometre.  
? Over the sea surface the friction is minimum. 
 
CORIOLIS FORCE  
Page 2


 
 
WINDS:  
? The air in motion is called wind.  
? Pressure differences force winds to flow from high pressure are to 
low pressure area. Pressure differences in turn are caused by unequal 
heating of the earth’s surface by solar radiation. 
? The wind blows from high pressure to low pressure.  
? Winds balance uneven distribution of pressure globally. 
? Winds help in transfer of heat, moisture etc. from one place to 
another. 
 
FACTORS AFFECTING THE WIND VELOCITY  
 
PRESSURE GRADIENT FORCE  
? The rate of change of pressure with respect to distance is the pressure 
gradient.  
? The pressure gradient is strong where the isobars are close to each 
other and is weak where the isobars are apart. 
? The pressure-gradient force is the force that results when there is a 
difference in pressure across a surface. 
FRICTIONAL FORCE  
? The irregularities of the earth’s surface offer resistance to the wind 
movement in the form of friction. 
? It is greatest at the surface and its influence children extends upward 
elevation of 1 - 3 kilometre.  
? Over the sea surface the friction is minimum. 
 
CORIOLIS FORCE  
 
 
? The rotation of the earth about its axis affects the direction of the 
wind.  
? It deflects the wind to the right direction in the northern hemisphere 
and to the left in the southern hemisphere.  
? The Earth rotates faster at the Equator than it does at the poles. 
? The Coriolis force is directly proportional to the angle of latitude. It is 
maximum at the poles and is absent at the equator.  
 
 
NOTE: 
JUST TO REMEMBER 
When you go up ;  relative to the ground ; you move ahead of everything 
else. 
When u come back to the equator u fall behind. 
 
 
 
EFFECTS OF THE CORIOLIS FORCE: 
 
? The direction of ocean currents is determined by the Coriolis 
force. 
? The wind blows in the direction determined by the Coriolis force. 
? In the northern hemisphere, wind passing from high-pressure 
belt to low-pressure belt turns towards the right. This creates 
anti-clockwise hurricanes. 
Page 3


 
 
WINDS:  
? The air in motion is called wind.  
? Pressure differences force winds to flow from high pressure are to 
low pressure area. Pressure differences in turn are caused by unequal 
heating of the earth’s surface by solar radiation. 
? The wind blows from high pressure to low pressure.  
? Winds balance uneven distribution of pressure globally. 
? Winds help in transfer of heat, moisture etc. from one place to 
another. 
 
FACTORS AFFECTING THE WIND VELOCITY  
 
PRESSURE GRADIENT FORCE  
? The rate of change of pressure with respect to distance is the pressure 
gradient.  
? The pressure gradient is strong where the isobars are close to each 
other and is weak where the isobars are apart. 
? The pressure-gradient force is the force that results when there is a 
difference in pressure across a surface. 
FRICTIONAL FORCE  
? The irregularities of the earth’s surface offer resistance to the wind 
movement in the form of friction. 
? It is greatest at the surface and its influence children extends upward 
elevation of 1 - 3 kilometre.  
? Over the sea surface the friction is minimum. 
 
CORIOLIS FORCE  
 
 
? The rotation of the earth about its axis affects the direction of the 
wind.  
? It deflects the wind to the right direction in the northern hemisphere 
and to the left in the southern hemisphere.  
? The Earth rotates faster at the Equator than it does at the poles. 
? The Coriolis force is directly proportional to the angle of latitude. It is 
maximum at the poles and is absent at the equator.  
 
 
NOTE: 
JUST TO REMEMBER 
When you go up ;  relative to the ground ; you move ahead of everything 
else. 
When u come back to the equator u fall behind. 
 
 
 
EFFECTS OF THE CORIOLIS FORCE: 
 
? The direction of ocean currents is determined by the Coriolis 
force. 
? The wind blows in the direction determined by the Coriolis force. 
? In the northern hemisphere, wind passing from high-pressure 
belt to low-pressure belt turns towards the right. This creates 
anti-clockwise hurricanes. 
 
 
? In the southern hemisphere due to the Coriolis force, the wind 
moves towards the left direction creating clockwise storms. 
? The long distance flights face the Coriolis force and hence the 
earth’s rotation is taken into account to determine the direction 
of flight. Therefore the flights between two cities never travel in a 
straight line even if the cities are located on the same latitude. 
? Same is the case with rockets, the rockets are launched towards 
the eastern direction generally near the equator, so that they do 
not get affected by the Coriolis force. 
? Same is the case with satellites ( but only with the equatorial 
ones). 
? Military aircraft also determine the impact of the Coriolis force 
before the launch because if the missiles come under the 
influence of the Coriolis force, they may land up on a different 
target.